CURRENT STATUS OF CINARA CUPRESSI IN BURUNDI:
ITS IMPACT ON FOREST RESOURCES AND CONTROL OPERATIONS*

By

Jean Bosco Sabukwikopa
Forest Researcher

and

Stanylas Muyango
Research Entomologist

ISABU, B.P. 795
Bujumbura, Burundi 

INTRODUCTION

Burundi covers an area of 27,834 km² and has a population of 5.4 million with a population growth rate of 3%. Available agricultural land is thus becoming scarce with the consequent clearing of marginal lands which are generally reserved for forests.

At the same time, demand for wood is also increasing, particularly for fuelwood and lumber. This increasing demand exceeds supply. The difficulty in finding non-demanding species for marginal sites which also grow rapidly has led to the use of exotic tree species with the aim of reforesting approximately 600,000 ha, or 20% of the land area. As a result, extensive plantations using Callitris, Cupressus, Eucalyptus and Pinus have been established.

CURRENT FOREST COVER

Wooded areas comprise 50,000 ha of natural forests and 72,917 ha of plantations. Plantations with species which are members of the family Cupressaceae and susceptible to Cinara cupressi cover 24,794 ha or 34% of Burundi's exotic plantations (Table 1).

Callitris and Cupressus sp. were established primarily for the protection of bare hill sides. For this purpose, it was necessary to use species exhibiting plasticity with respect to environmental adaptability, particularly those capable of growing on skeletal soils while exhibiting rapid growth rates. Thus plantations have often been established on marginal sites in relation to their ecological adaptability.

TABLE 1
AREA OF EXOTIC TREES ESTABLISHED IN BURUNDI

As early as 1981, F. Brunck observed cypress dieback and suggested: "It is difficult to determine the cause of this dieback. Apparently, it is not a problem of parasites, although some attacks (rats, caterpillars etc.) can cause wounds which are likely to favour the dieback. But it seems to be a question primarily of soil and, to a lesser extent, climate. The last factor being reputed not to be of the most favourable for Cupressus lusitanica."

The same observation might equally be applied to Callitris.

Cinara cupressi thus encountered plants in a weakened state, subject in some areas to dieback which has been attributed to the poor quality of soils.

FIRST OCCURRENCE OF THE INSECT

The first records of Cinara cupressi were made in November 1988 in the south of the country, while the occurrence of damage in the north dates from 1989. Damage symptoms include drying out of the branches and the presence of honeydew and sooty moulds. In 1989, there was a rapid spread of the aphid covering most of the areas where Callitris and Cupressus have been planted.

It should be noted that there are species differences in susceptibility. Cupressus sp. are attacked first while Callitris sp. are attacked later. A gradual increase in resistance can be found as we move from Cupressus lusitanica to Callitris glauca, C. robusta, and C. calcarata.

The strong increase in aphid numbers during the main dry season has caused significant damage, particularly at high elevations where cypress and callitris are planted on poor skeletal soils. In the eastern part of the country, on the plains, the attacks have not been as severe. This could be an elevation effect or be due to different soils. On the plains, the soils are relatively deep.

From the available evidence and given the severity of the attack on cypress and callitris, we conclude that the aphid is a relatively recent introduction into Burundi because its presence was not detected despite surveys of the aphid fauna dating back to 1979. It is probable that the aphid entered from the south as it was recorded in Malawi in 1986, Tanzania in 1987 and Burundi in 1988.

CONTROL STRATEGY IN BURUNDI CHEMICAL CONTROL

In Burundi, chemical control of Cinara cupressi is economically and practically unrealistic. Wide scale chemical control in the cypress and callitris forests would be extremely expensive. Furthermore, the practical difficulties of spraying the affected trees which are sometimes widely dispersed would further increase control costs. Spraying has been limited to hedges around homes.

BIOLOGICAL CONTROL

Since Cinara cupressi is a recent introduction to Africa, biological control would be a realistic proposition, particularly since in its area of origin (Europe), its natural enemies regulate its numbers more or less effectively.

Within the framework of its program of biological control of aphids in general, the Institute of Agronomic Sciences of Burundi (ISABU), in collaboration with foreign institutions envisages the introduction of parasites specific to Cinara. With this in mind, Dr. Stary of the Entomological Institute of Czechoslovakia, with whom we collaborate, intends to use the genus Pauesia which parasitizes various species of Cinara in Europe. He also intends to use a coccinelid which controls Cinara well in Czechoslovakia. However, the complex of parasites of this particular aphid is not well understood in Europe where C. cupressi originates.

PRESENT OVERALL CONTROL STRATEGY

The present overall control strategy for C. cupressi in Burundi can be summarized into three points:

1. Stop further planting of cypress and callitris and search for alternative species (Grevillea, Eucalyptus, Acacia etc).

It should be noted that Callitris gives poor results on shallow soils. It grows poorly after about three years of age and produces very little leaf litter. With its fastigiate (narrow) crown, this species is not useful for soil protection. While the local cypress sources are of restricted genetic base, a number of new provenances have been introduced at the research level by ISABU.

2. Harvest all trees old enough to be utilized. This would allow the creation of uneven aged stands. It is believed that the degree of resistance or susceptibility to a pest varies as a function of species and age of the trees. This would minimize the risk of rapid spread of a pest.

3. Identify resistant individuals as we have noted that there were some healthy individuals in affected stands.

This strategy has allowed us to:

Avoid erosion problems through the avoidance of clearcutting.

Establish mixed plantations in cut over areas.

Follow the course of development of the pest.

THE DEVELOPMENT OF THE EPIDEMIC

Cinara cupressi was first observed in November 1989. Following its discovery, it was noted that populations decreased in April 1990. This reduction in aphid numbers could be due, in part, to rain which dislodges the insects and to the development of a parasitic fungus (family Entomophthorales). These factors, along with local predation by coccinellids, syrphids, lacewings (families Hemerobiidae and Chrysopidae) and spiders, tend to regulate aphid numbers more or less effectively.

At the present time, we are wondering whether these natural enemies are successfully maintaining populations of this pest at a level where it will not cause significant damage.

RESEARCH ACTIVITIES 

For the present time, research priorities are to:

1. Study the bio-ecology of Cinara cupressi and determine the various causes of population increase.
2. Inventory the various natural enemies and determine their effectiveness in controlling Cinara cupressi.
3. Continue with the diversification of genera, species and provenances to obtain resistant material and to allow the establishment of mixed plantations.

* Translated from French by Jean S. Brouard, Silvagen Associates LTD, Edmonton, Canada.

EXOTIC CONIFER APHIDS IN KENYA, THEIR CURRENT STATUS AND OPTIONS FOR MANAGEMENT

By

A. L. Owuor
Kenya Forest Research Institute
P.O. Box 20412
Nairobi, Kenya 

SUMMARY

Kenya, like several other African Countries, relies on exotic conifers for most of it's commercial softwood products. To meet this demand, we have established through the years, tens of thousands of hectares of cypress and pines. These plantations have been relatively free from serious insect pests apart from the occasional defoliators which have never been of grave concern. However, in the recent past, damaging exotic aphid species have invaded these plantations and, in some instances, serious damage has resulted. These aphid species include; the Eurasian pine woolly aphid, Pineus pini (Macquart), the holarctic pine needle aphid, Eulachnus rileyi (Williams) and the European cypress aphid, cinara cupressi (Buckton) (Table 1).

TABLE 1  

STATUS OF CONIFER APHIDS IN KENYA

PINE WOOLLY APHID

Of the three exotic conifer aphids, Pineus pini (Macquart) was the first to be recorded in Kenya. This was way back in 1968. In the 60's we were involved in projects aimed at improving our conifer germ plasm and we often relied upon the importation of vegetative material from other countries. P. pini found its way into this country through this same material that was meant to improve the country's softwood supplies.

This aphid was first noticed at the Muguga plant quarantine station on Pinus caribea grafted material from Australia. Aided by wind, the aphid spread rapidly in the months that followed. In these first months, observations made indicated that 90% of P. radiata within the infested area had been attacked, 51% having experienced heavy infestation, with growing leaves yellowing and older ones loosely attached to the branches. P. patula had about 70% attack. the situation looked grim and in the ensuing panic it was ordered that all host plants of the aphid in the area be destroyed. this was done in the hope that the pest was still confined to Muguga, but it turned out to be otherwise. This hurried action destroyed several selected provenances of pines from all corners of the globe that were to be found in the arboretum and tree bank at Muguga.

Once it was realized that the aphid had, in fact, spread beyond the gazetted quarantine area, alternative solutions to the problem were sought. Various control options were then investigated. they included pesticide application, natural enemies and silvicultural control by planting of less susceptible species of pines. Effective control was achieved with 0.075% BHC and Dimethoate 0.05%, but cost and benefit analysis ruled out large scale applications in plantations. These results were therefore confined to nurseries, seed orchards and tree banks.

Late in 1969, once it was obvious that pesticides would not solve the problem, due to prohibitive costs, biological control was suggested. Past experience with the Eucalyptus snout weevil, in 1945, had proved to us that this was a possible way out of the situation. the International Institute for Biological Control (IIBC), then Commonwealth Institute for Biological Control (CIBC), was contacted for assistance. After surveys in Asia and Europe, candidate insects were made available for releases into Kenya. Releases were made between 1970 and 1975. The first predators released were Scymnus suturalis, S. niqrinus and Leucopis tapiae, all collected from Europe. They all failed to establish. Next in line were Leucopis nigraluna and L. argenticollis. They also failed to establish. The anthochorid, Tetraphleps raoi, was released in Kenya for the first time in 1975. The introduction was from Pakistan. It established well but its success as a bio-control agent for the pine woolly aphid in Kenya is highly doubted. Work to determine its efficacy is still underway.

Prior to the pine woolly aphid outbreak in the late 1960's, a lot of emphasis had been placed in the planting of the fast growing, high yielding P. radiata. this had to change as this species had proven to be more prone to aphid attack. P. patula, which had shown greater tolerance was therefore the natural choice. Its yields were lower than those of radiate but were acceptable.

THE HOLARCTIC PINE NEEDLE APHID

The pine needle aphid, Eulachnus rileyi (Williams), is a less common exotic aphid pest in our pine forests. Since its first record from the foot of Mt. Elgon in 1988, this aphid had not spread to other pine growing areas in Kenya. Not much is known of its economic importance to pines locally. It established much smaller colonies as compared to the other two aphids. Affected needles turn yellow and drop off prematurely. Infestations in plantations are normally scattered. The worst we have seen are trees with roughly 10% of the foliage yellow. This is normally spread evenly all around the crown of the trees. What we are certain of is that the aphid has a preference for P. patula. Research on this aphid is currently centred around literature search and its annual spread in the country. We do not anticipate it developing into a serious pest soon. It is not known for sure how this insect got into Kenya, but the fact that it was first observed near the Kenya/Uganda border seems to indicate that it could have flown across this border, assisted by wind.

THE EUROPEAN CYPRESS APHID

The cypress aphid Cinara cupressi (Buckton), is by far the most dangerous of the three conifer aphids. Not only does it kill trees fast but it is also capable of covering large areas rapidly through strong flying alates, assisted by air currents. As is well known, this insect's first record is in Malawi during the year 1986. By 1990, it had found its way into Kenya. The infestation in Kenya had spilled over from that in neighbouring Tanzania and therefore began in the south. In just one year this insect had spread to all cypress growing regions of the country.

This aphid is capable of killing fully grown trees in three months. damage to plantations has been as high as 90% in some cases. We in Kenya have a lot at stake. Cupressus lusitanica is currently the most widely planted softwood species. Out of 167,000 ha of softwood plantations, it forms 44%. Juniperus procera, which is also attacked by the aphid, but to a lesser extent, covers some 200,00 ha in the water catchment areas. This aphid is causing severe devastation to Cupressus sp, Callitris sp, and Widdringtonia sp. From its first point of entry, it spread fast in a N.W. direction aided by wind.

When first detected in the small town of Kiseran, attempts were made to eradicate all its host trees from the region but the lesson taught in 1968 was repeated. The insect had spread too fast for us to contain the outbreak in this area.

We then opted for the alternative control measures. we chose to adopt the IPM approach for this problem. A joint collaborative proposal was therefore prepared by KEFRI, Forest Department, ICIPE and IIBC as players.

A wide variety of pesticides have been screened with varying results. Some are listed in Table 2.

TABLE 2

PESTICIDES SCREENED AGAINST 
CINARA CUPRESSI

Most of these are broad spectrum insecticides. More studies are still underway with selective aphicides such as Ekatin and Pirimor. Various modes of pesticide application have also been tested. Soil applications of systematic pesticides failed to work even on young hedges. Aerial application has been ruled out as we foresee great difficulty in the penetration of the dense canopy. We have experimented with two methods of application; high volume, back mounted motorised sprayers and shoulder mounted warm fog generators. The former has the disadvantage of requiring very high volumes of water, which is difficult to supply under rugged field conditions. It is also limited by the height to which it can spray. Warm fog generators are capable of reducing the man hours for spraying by two thirds. The fog is able to rise to the top of the trees and the drift makes it possible to cover a wide area with a single pass.

Even with more efficient methods, pesticides are still very expensive and can only be applied to selected crops for a limited time only. Pesticides will therefore be only applied to contain sudden explosions of the aphid population in high value crops, defined as seed orchards, tree banks and plantations under the age of 15 years. As we anticipate bio- control to be on the ground by the end of year three of the project, chemical control will be concentrated in these first three years.

Biological control is one of our long term management strategies for C. cupressi. While surveys are being undertaken in Europe, Asia and North America by the IIBC, we are engaged in studies of the insect's basic biology in preparation for introductions of the natural enemies within the next few years.

Natural enemies used alone may not produce the best results, from our experience with the pine woolly aphid, replacement of highly susceptible species is also a very important management tool. In this past year we have noticed several varieties of Cupressus lusitanica that have survived the worst onslaught by the cypress aphid. Two mechanisms seem to be in play. In some instances the trees have been totally avoided by the aphid and others are able to withstand attacks by the aphid. We could therefore talk of either resistance or tolerance to the pest. There is also a marked difference in the level of tolerance of various species of Cupressus. These trees will form the base population from which resistant tree crops for plantation establishment will be drawn. Our research proposal also addresses itself to this area of genetic control.

CONCLUSION

Today's world has been made smaller by the efficient transportation network that links practically all cities on the globe. Even the strictest quarantine regulations will not be able to prevent the entry of minute pests such as the aphids from other continents. We should therefore expect to see in the future, more and more of our exotic trees being attacked by their natural pests that they have hitherto been isolated from. Our efforts should therefore be on early detection for prompt management of such pests.

The problems caused by these three conifer aphids is not unique to Kenya. Several other African countries are experiencing the same problem. the search for a solution should therefore be a regional effort where activities undertaken by each country complement those of the others. This will not only improve the ties between the national forestry research programmes of the affected countries, but will also save valuable time and resources, that would otherwise have been wasted by duplication of efforts.

REFERENCES

Aloo, T. C. and M. K. Karanja, 1986. The bio-control of the pine woolly aphid in Kenya using Tetraphleps raoi. Egerton Univ. Col. Res. no 10.

Brown, K.W., 1970. Testing of insecticides against Pineus sp in east Africa. East Africa Agr. Journal, 36:200-201.

Katerere, Y., 1982. Aphid density and animal damage to Pinus patula Schiede and Deppe in a clone bank at Melsetter Forest Research Station. S. Africa Forest Jour, 122:63- 65.

Kfir, R., F. Kirsten and N.J. Van Rensburg, 1985. Pauesia sp. (Hymenoptera:Aphidae), a parasite introduced into South Africa for the bio-control of the black pine aphid, Cinara cronartii (Homoptera:Aphidae). Environ. Entomol. 14:597-601.

Mailu, A.M., C.P.M. Khamala and D.J.W. Rose, 1982. Establishment of the pine woolly aphid, Pineus pini (Gmelin) Adelgidae, on some host trees in Kenya. Jour. Sci. Tech. Biol. Sc. 3:61-68.

Mills, N.J., 1990. Biological control of forest aphid pests in Africa. Bull. Entomol. Res. 80:31-36. 

Odera, J.A., 1969. A new genus and species of Homoptera in Kenya. Kenya Forest Dept. Tech Note 125.

Odera, J.A., 1970. Accidental introduction of Pineus into E. Africa. Kenya Forest Dept Tech Note 129.

Odera, J.A., 1971. Insecticidal control of Pineus sp. (Homoptera:Adelgidae) in East Africa. Pans 17:464-467.

Odera, J.A., 1974. The incidence and host trees of the pine woolly aphid, Pineus pini (L) in East Africa. Comm. For. Rev. 53:128-136.

Odendaal, M. 1980. Eulachnus rileyi: a new pest on pines in Zimbabwe. S. Afr. For. J. 115:69-71.    

THE STATUS AND DEVELOPMENT OF CONIFER APHID DAMAGE IN MALAWI

By

C.Z. Chilima
Forestry Research Institute of Malawi
Box 270, Zomba, Malawi

INTRODUCTION

The establishment of major forest plantations in Malawi started in the 1930's involving mostly exotic conifer species which were planted in industrial plantations for sawn timber and other industrial purposes. Eucalypts were also planted mainly to provide construction poles and fuelwood. The total planted area since then, covers more than 74,000 hectares and the largest proportion of this is composed of conifer species, mainly Pinus patula and P. kesiya. Cupressus sp. and Widdringtonia nodiflora occupy a minor portion of the total planted area, but they are widely used as ornamental, shade and ceremonial trees. W. nodiflora is a source of precious and durable timber and is designated the National Tree of Malawi. Natural forests of this species are found on Mulanje Mountain.

These plantations provide 90 % of the wood fuel to the population of Malawi and employment to more than 10,000 people. They also make the country self sufficient in timber and construction poles, and have a high water, soil, fauna and flora conservation value.

Since the initiation of their establishment in the 1930's, the conifer plantations have enjoyed a relatively pest free period. This period, however, has been broken by the appearance of the three conifer aphids; Cinara cupressi, Eulachnus rileyi and Pineus pini. Within the past 10 -15 years, these pests have appeared in succession in the plantations, and are causing considerable damage.

This is a brief report of the status and development of the damage that each of the three conifer aphids is inflicting on the conifer plantations of Malawi.

PINE NEEDLE APHID, EULACHNUS RILEYI

This pest was first found in Africa in the later 1970's in Zambia and Zimbabwe (Marchant 1981). It was first reported in Malawi in 1979 when it was causing non-fatal damage to Pinus patula and P. kesiya in Dedza and Viphya Forest. It has since spread to all parts of the country attacking almost all pine species (Odera 1991).

The pest appears to feed on senescing or mature needles throughout the crown. This causes a characteristic mottling and yellowing of the pine needles which eventually get cast prematurely. Damage seems to be most severe during the dry season which coincides with peak aphid population. During the rainy season. all trees appear to recover and aphid populations are very low.

PINE WOOLLY APHID, PINEUS PINI

The pine woolly aphid was first recorded in Africa in 1968 from Zimbabwe and Kenya (Odera 1974, Barnes, et al 1976). In Malawi, the first occurrence of the pest was in 1984 when it was attacking Pinus kesiya in Dedza Forest. By the end of 1985, 1,500 ha of P. kesiya had been attacked to various extents. Tree mortality during this outbreak was low. For a period of about three years, the pest seemed to be restricted to Dedza Forest and on P. kesiya and P. radiata only. However, in 1988, it was reported from Ndirande Forest and by 1989, it was found in all major forests of the country, attacking practically all pines that are grown in Malawi. (Odera 1991).

Infested trees have white mats of wool between the bud scales and bases of the growing needles. Heavy infestations led to the death of needles and gouting and death of leading shoots (Odera 1991). Pinus kesiya and P. patula were the most heavily infested and, in severe cases, whole trees were killed.

It has been observed that infestations are most severe during the dry season but they persist throughout the year.

CYPRESS APHID, CINARA CUPRESSI

The first record of this aphid in Africa was in Malawi in August, 1986, when specimens were found on Cupressus lusitanica. According to Magembe (pers. comm.), symptoms of damage by the pest were observed earlier in the Musoma area, Tanzania in 1985, but this record has not been published. In Malawi, the pest was first found in the northern region, in the city of Mzuzu and the Viphya Forest (Chilima 1989).

The year 1986 had an abnormally long dry season and had an annual rainfall which was about 17 % lower than the average for the period 1978-1987. This appeared to have favoured rapid buildup of the aphid population. Within a period of one year, the pest had spread throughout the Viphya Forest, attacking C. torulosa and Widdringtonia nodiflora as well as C. lusitanica. By the end of 1988, C. cupressi had also spread southwards and was reported from the whole country, wherever its host trees were growing.

Close inspection showed that damage symptoms developed when colonies of the pest were feeding on the smaller twigs of the host trees. Each year, damage appeared to be most severe during the dry seasons (June-October). This coincided with peak populations of aphids; as many as 100 individuals per 30 cm of twig. The aphids induced yellowing and browning of foliage immediately surrounding their colonies. Where infestation were high or persistent, this led to death of branches and sometimes of whole trees. During the rainy seasons, aphid populations declined and those trees which had not been killed showed some signs of recovery. However, it was observed that most trees did not recover after two or three seasons of attacks.

Surveys conducted in the Viphya Forest showed that a number of predators, mainly syrphid larvae and coccinellids were feeding on the aphids but were not effectively reducing their populations.

LOSSES DUE TO APHIDS SO FAR

Financial losses due to Cinara cupressi damage in Malawi were estimated by Odera (1991). It was estimated that by the end of 1990, the pest had inflicted losses of about $US 2.4 million on the standing crop of cypress and cedar and another US$ l million on increment.

Losses due to the two pine aphids as of the end of 1990 were estimated at $US 2.6 million on the standing crop and a further $US 2.6 million on annual increment (Odera 1991). Recent observations indicate a rapid increment in mortality of pines due to P. pini; and therefore the loss on standing crop is likely to be much higher than $US 2.6 million.

The value of the different tree species for soil, water, fauna and flora conservation is difficult to quantify in monetary terms. So is the value of Cupressus sp. as ornamental, hedge and ceremonial trees and that of Widdrinatonia nodiflora as the National Tree of Malawi. The financial losses mentioned above therefore, are underestimates of the real damage that the conifer aphids are causing in Malawi.

INTERVENTIONS AND FUTURE PROGRAMS

BIOLOGICAL CONTROL

A programme of classical biological control was initiated through consultations with the International Institute of Biological Control (IIBC). The programme is being funded by ODA. Surveys for natural enemies are already underway in Europe. Meanwhile, pre-release preparations are being carried out in Malawi. It is hoped that releases will be done within the next two years.

CHEMICAL CONTROL

Several insecticides are being screened for possible use in control of aphids in nurseries, Christmas tree stands, hedges, orchards and research trials. So far, fastac, with an LC 50 of 1.5 ppm followed by fenitrothion with an LC 50 of 1.8 ppm for C. cupressi appears to be the most effective. Work on this will continue.

SILVICULTURAL CONTROL

Recommendations were made to stop further establishment of Cupressus lusitanica in the country, and to clearfall all severely damaged stands. Alternative hedge species were recommended.

BIOLOGY AND ECOLOGY

Studies have been initiated to determine the

reproduction, development and population dynamics of the three aphids. Work on this is in progress and will continue until the biology and ecology of the aphids in Malawi is established.

MONITORING

Monitoring of the development of the aphid problems has been conducted in the Viphya Forest since they were first reported. This will continue and will be expanded to cover more forests.

REFERENCES CITED

Anon, 1990. Economic impact of exotic aphid pests, Cinara cupressi, Eulachnus rileyi and Pineus sp. on exotic conifer forestry plantations and woodlots in southern and eastern Africa. IIBC, UK.

Barnes, R.D. 1976. Introduction, spread and control of the pine woolly aphid, Pineus pini (L.) in Rhodesia. South African Forestry Journal, 90:1-6.

Chilima, C.Z. 1989. Cinara cupressi: a pest of Mulanje cedar and cypress trees in Malawi. FRIM Report No. 89009.

Marchant, L. 1981. The pine needle aphid, Eulachnus rileyi Williams (Homoptera:Aphididae). Pests and Diseases of South Africa, No 273, 4 pp.

Odera, J.A., 1974. The incidence and host trees of pine woolly aphid, Pineus pini (L.) in east Africa. Comm. For. Review, 53:128-176.

Odera, J.A., 1991. Some opportunities for managing aphids of softwood plantations in Malawi. Assistance to Forestry Sector, MLW/86/020, Malawi, FAO, Rome.

A REVIEW OF THE PINE WOOLLY APHID, PINEUS PINI (L.), A PEST OF PINE PLANTATIONS IN TANZANIA

By

Alfred Massawe
Tanzania Forest Research Institute
Silviculture Research Centre
P.O. Box 95
Lushoto, Tanzania

SYNOPSIS

In the early seventies, Pineus pini (L.) was first noted in Tanzania, where it has become an important pest of pine plantations. This paper reviews the literature available on the aphid and summarises preliminary observations of the pest in Tanzania.

INTRODUCTION

In Tanzania, several plantations have been established by the state to supply raw materials to wood based industries in the country. The main softwood species under planting include Pinus patula, P. caribaea, P. elliottii and Cupressus lusitanica. Other species planted on a small scale include P. kesiya, P. oocarpa, and P. taeda. The softwood plantation forests cover more than 60,240 ha. based on data collected in 1981 (Forest Division 1982).

Pests and diseases are among the severe problems facing most of the industrial plantations in the country. Pest infestation to forest stands causes growth retardation, death of plants and lowers the quality of the final crop, hence the products are sold at lower prices.

Pine woolly aphid, Pineus pini, (Adelgidae) is among the problematic pests that attack most of the pine species. Problems of pine woolly aphids were first noted in the country in the early 1970's at the Sao Hill Forest Project. The infestation was so severe that the infested trees were cleared as part of remedial measures to combat the spread of the pest. Chemical such as propoxur at 0.5% and endosulfan at 1% concentration were tried and biological control using a predator, Tetraphleps raoi (Ghauri) was also tried with little success.

The pest has now spread to almost every pine plantation in the country. Although various methods were employed, hardly anything is reported on the real effects of the pines and the critical population density of aphid which can cause severe damage.

This paper attempts to show the efforts taken to control pine woolly aphids in the country and their success.

BACKGROUND INFORMATION

In general, many of the woolly aphids of the genera Adelges and Pineus (Homoptera:Adelgidae) are not known to be pests in the holarctic temperate zones. They have been introduced into the tropics accidentally through afforestation programmes with the temperate zone softwood species (Odera 1971).

It was also mentioned that Pineus pini was introduced to Muguga, Kenya from Australia on pine scions. In 1969, a well established infestation of Pineus sp. was found on about 38 species of pines in the East African Agricultural and Forestry Research Organization's (EAAFRO) arboretum at Muguga and in the neighbouring farms in the Muguga reserve in Kenya. These were the only recorded occurrences of Pineus in Africa south of the Sahara. From Muguga, grafted materials were distributed to Sao Hill and West Kilimanjaro in Tanzania (Odera 1971,1974).

After the discovery of the infestation at Muguga, a reconnaissance survey was conducted in areas where the grafted materials were distributed, that is Muguga, Sao Hill and West Kilimanjaro. The survey revealed that some trees were infested in seed orchards and in stands planted in 1967 at Sao Hill, the seed orchard planted in 1968 at Muguga (Kenya) and West Kilimanjaro in Tanzania.

Odera (1974) pointed out that the plots of seed orchard of pines planted before 1967 in Sao Hill and 1968 in Muguga and West Kilimanjaro were not infested by woolly aphid. It was then concluded that the pest was introduced to Sao Hill and West Kilimanjaro through seedlings from Muguga. From that time (1967), the pest spread rapidly to some of the forest plantations in the country including the Meru Forest Project in Arusha, Rongai and West Kilimanjaro in the Kilimanjaro region.

SYMPTOMS OF PINEUS PINI INFESTATION

The symptoms of P. pini attack is the white, woolly appearance on the infested parts of the plant. This happens when the aphid infestations moderate to heavy. The older growing needles below the growing shoot turn yellow to reddish. Change in colour begins at the needle tips and extends to the base. Loss of older needles, extensive chlorosis, deterioration of young needles and combined colour of the mould provides a clear indication of severe Pineus pini attack before the tree dies.

Retardation in height growth and diameter increment (basal area) is also experienced (Odera 1972). Trees may recover from aphid attack but such trees look unhealthy (Kisaka 1976).

DAMAGE CAUSED BY PINEUS PINI

The effect of P. pini attack on pines varies with the host species and with the severity of aphid infestation. The research carried out by Zwolinski et al (1988) in South Africa showed that P. pini infestations reduce the seed production of Pinus pinaster by 23% in mature cones. The aphid caused abortion of female strobili and the death of immature cones (Odera 1972) which probably reduces the number of mature cones on the tree. Zwolinski further pointed out that an average of 31.8% of the total collected cones were affected; mean mass, volume, length and width of cones was reduced by 50.3%, 38.3%, 22.5%, and 15.3% respectively when compared to unaffected cones. The total number of seeds obtained from affected cones was reduced by 74.7%.

The full effect of P. pini in East Africa is not fully known. At present the relationship between the feeding of P. pini and the damage caused to its host is still doubtful.

The close relationship between the damage and the loss of yield has been demonstrated by Austra (1970) who found out that 100% defoliation of Pinus patula resulted in 50% growth reduction.

According to Kisaka (1976), trees with small diameter are more affected by the insects than trees with large diameters. The study conducted by Kisaka (1976) at Sao Hill (Tanzania) showed that increment in basal area of the attacked tree is 1.14% less than that of unaffected trees. It was also shown that uninfested trees grow in height by 1.14% than that of infested trees.

A study to determine the effect of P. pini on the cumulative growth of seven year old Pinus patula and the critical population density which can be harmful to the pine (Rwamputa 1987) in the Meru Forest Project showed that there is a negative correlation between aphid density and cumulative growth retardation by 82.32%. Severe damage was found to begin at a density of about 0.88 aphids per centimetre.

CONTROL OF PINEUS PINI

The control of pine woolly aphid at Sao Hill has been dealt with to some acceptable degree. It was found that spraying with thiodan and Teepol 1% solution and propoxur (Baygon E.C.) was effective but expensive. Chemical control has now been ruled out due to the high costs and spray difficulties (The insect is protected by a waxy wool).

The recommended control method of pine woolly aphid is biological control. Bennett and Ostmark (1972) have suggested that the application of biological control is the only way to manage this pest. This was also supported by Odera (1971) who unsuccessfully used chemicals to eradicate the pest. Odera's

failure was due to insect habitat, feeding habit, cost and the effect of chemicals on the environment. It was suggested to use chemicals in the nurseries only. The main attraction of biological control is that it obviates the necessity of using chemical poisons and in its most successful case, gives permanent control from one introduction (Hill 1975). This method of control is most effective against pests of exotic crops which often do not have their full compliment of natural enemies in their introduced localities.

In Tanzania, native predators such as the Coccinellids, Chaelemens sp., Chilocorus sp.,and Rodolia sp. have been found keeping down the aphid population in some pine plantations in the Sao Hill, West Kilimanjaro and Meru Forest projects (Kisaka 1990, personal communication). Various exotic predators which have been evaluated for control of P. pini include:

Diptera: Chamaemydae

Leucopis nigraluua
L. manii
L. tapiae
Leucopis sp.

Coleoptera: Coccinellidae

Ballia eucharis
Scymnus sp.

These predators were caged and released on Sao Hill in Tanzania and Muguga in Kenya in pine plantations infested by P. pini. Another predator introduced into Sao Hill after being reared in Muguga, Kenya was Tetraphleps raoi (Hemiptera: Anthocoridae) (Kisaka 1976). Most of these predators have been found feeding on the aphids, hence helping in suppression of the pest. Among the predators released, T. raoi was found to be effective. This insect is multivoltine and is known to attack only Pineus sp. Its feeding habit in all life stage is promising for its value as a biological agent against P. pini.

Apart however, from the question of biological control methods, it is probable that further knowledge of the silvicultural requirements of our forests and the prospects of breeding for resistance of pines to control the aphid will enable the forester to deal more effectively with pine woolly aphid in plantations.

ACKNOWLEDGEMENT

The author acknowledges FAO for inviting him to this workshop.

REFERENCES

Austra, O., 1970. The effect of artificial defoliation on the growth of P. patula in East Africa. East African Forestry Journal, 36:114-118.

Bennett, w. H. and H. E. Ostmark. 1973. The insect pests of southern pines. USDA, Forest Service, Southern Forest Experiment station, New Orleans, Louisiana (USA).

Hill, D.S., 1975. Agricultural insect pests of the tropics and their control. pp 79-98.

Forest Division, 1982. Management practices in conifer plantations in Tanzania: Notes on forest operations.

Kisaka, E.E., 1976. Special studies on the woolly aphid (P.pini) at Sao Hill.

Odera, J.A., 1971. Insecticidal control of Pineus sp. (Homoptera:Adelgidae) in East Africa. Pans 17:464-467.

Odera, J.A., 1974. The incidence and host trees of the pine woolly aphid (Pineus pini (L.)) in East Africa. The Commonwealth Forestry Review, 53:128-136.

Rwamputa, A.K., 1987. The effect of woolly aphid (Pineus pini) on quantity of Pinus patula. Timber Utilization Research Centre.

REVIEW OF THE CYPRESS APHID IN TANZANIA

By

B. S. Kessy
Regional Natural Resources Officer
Coast Region
P.O. BOX 30080
Kihaba, Tanzania

INTRODUCTION

Tanzania is the largest country in East Africa with an area of 940,000 km². Forests and woodlands occupy about 44 million hectares which are distributed into 1,400,000 ha of natural forests, 80,000 ha of mangrove forests and 42,891,000 ha of woodlands.

About 13,024,000 ha have been gazetted for production and catchment purposes. within the forest reserves, there are plantations which occupy an area of about 80,000 ha. Species planted include Tectona grandis, Pinus radiata, P. patula, Eucalyptus sp., Cedar, Podo, Cupressus sp., Olea africana and Grevillea robusta.

OUTBREAK OF CYPRESS APHID

The drying of the cypress trees was reported in June 1987 in two regions in the north, i.e. Arusha and Kilimanjaro and three regions in the southern highlands, i.e. Mbeya, Iringa and Ruvuma.

A team of scientists consisting of a soil scientist/plant nutritionist, plant pathologist and forest entomologist was sent to the affected regions with the following objectives:

1. To assess the extent of the disease and establish its causes.
2. To evaluate possible control measures.
3. To recommend remedial measures.

FIELD SURVEYS

The team conducted a field survey and observed the drying of trees belonging to the family Cupressaceae at the following levels:

1. At the plot level, most trees were either dry or green and sometimes were sandwiched between an array of dry ones.
2. At the tree level, two drying patterns were observed. Either the apical shoot started drying, thus extending to the entire tree or a significant portion of its foliage. Or sometimes the drying was reversed starting from the bottom of the crown and then extending to the apical shoot. This latter drying lead to a few deaths because recovery occurs if the rains come prior to the drying of the apical shoot. This drying pattern occurred in valley bottoms or level ground.

The drying trees in the Mbeya and Iringa Regions were found to have dark, grey coloured, bumble bee looking aphids. No aphids were observed in the other regions.

SCIENTIFIC STUDIES

During the survey, the team embarked on the following scientific studies:

1. Soil fertility status in relation to the problems of drying cypress species.
2. Entomology - entomological problems.
3. Pathology - pathological problems.

SOIL FERTILITY STATUS IN RELATION TO THE PROBLEMS OF DRYING CUPRESSUS SP.

METHODS

Soils were sampled in 18 profiles with an auger to a depth of 100 cm assuming this to be the maximum rooting depth for Cupressus lusitanica. Soils were sampled beneath the affected trees. In other areas fresh soil profiles were opened up or use was made of sawyers pits found adjacent to affected trees. These were subjected to chemical and mechanical analysis for the following parameters:

1. Organic carbon (%C)
2. Total nitrogen
3. C/N
4. P, Ca, Mg, K, Na, Cu, Zn, Fe, Mn
5. % Clay

Rainfall data for 1987 in relation to previous years was collected.

RESULTS

The soils of the southern highlands are comparatively poorer than soils in the northern parts. Hence drying of cypress in the south was more acute than in the north.

There is widespread deficiency of copper in the south. Soils in the north are experiencing manganese deficiency.

In some stations rainfall was a bit lower in 1987 compared to the previous years.

It was observed that drought, copper and aphid infestation could be the causative agents in the southern highlands while drought and nutrient deficiencies such as manganese could be the causative agents in the north.

PATHOLOGICAL STUDY

During the survey, an attempt was made to diagnose diseases caused by various pathogens such as fungi, bacteria and viruses. Infected plant parts were examined in the field, collected and taken to the laboratory for identification.

The various genera of fungi observed were:

1. Armillaria sp.
2. Phytophthora sp.
3. Fusarium sp.
4. Aspergillis sp.

These fungi do not damage trees due to improved silvicultural techniques. Hence all were found to be weak pathogens.

THE CASE OF CYPRESS ATTACK BY CINARA CUPRESSI IN RWANDA

By

Nsengidiana Jean Claude and Musabima Fanstin
ISAR, B.P. 671
Butare, Rwanda

STATUS AND IMPORTANCE OF CUPRESSACEAE IN RWANDA AFFORESTATION

In Rwanda, artificial plantations cover 206,900 ha. Fifteen percent of these plantations are of trees of the family Cupressaceae. Introduced since the 1930's, the following species are represented.

Callitris:

C.robusta
C.calcarata
C.quadrivalis

Cupressus:

C. lusitanica lusitanica
C. lusitanica benthamii
C. torulosa
C. sempervirens
C. arizonica
C. funebris

Juniperus

J.bermudiana
J.procera
J.virginiana

Thuja orientalis

Widdringtonia

W. cupreses
W. schwarzii
W. whytei
W. juniperes
W. dracomontana

Among these species, Cupressus lusitanica, P. lusitanica benthamii, Callitris robusta, and P. calcarata are widespread in economic and rural plantations.

BACKGROUND OF THE PEST, CINARA CUPRESSI

In Rwanda, the first attacks were recorded in January and February, 1989 in the southern part of the country near the border with Burundi. From there the pest spread toward the west of the country where there are many cypress plantations.

A group of entomologists and foresters in Rwanda, accompanied by a consultant (Dr. Benz) did a survey throughout the country up to Burundi and concluded that:

- The aphid Cinara cupressi was the causal agent.

- There was no fungal or virus disease.

- The gravity of the pest was in relation to the degree of soil fertility.

- The effect of the disease started inside the tree canopy outwards for individual trees and from the interior of plantations outwards.

- There are some trees which apparently have a natural resistance.

- Among trees widely planted, the severity of attack runs from Cupressus lusitanica lusitanica. C. lusitanica benthamii, Callitris robusta, C. quadrivalis, Cupressus torulosa, C. sempervirens and C. funebris. C. torulosa and C. funebris were free from attack.

- Although cypress are attacked, there are some individuals where recovery has started to progress. This began after November 1989 and the percentage varies according to edaphic and ecological conditions. In high altitudes, few trees are gaining needles while at mid altitudes, this phenomenon is evident.

- Pruning and thinning operations in attacked plantations increase the death of remaining trees because it reduces respectively the area of photosynthesis and the number of trees to be attacked, hence there is a concentration of many insects on a small area or on a few trees.

- The removal of sensitive species leads to attack on resistant species.

- The aphid is exclusively a monoecic species with a biologically complex cycle including parthenogenetic and sexual cycles. It appears that the parthenogenetic cycle is predominant under Rwanda conditions.

- The attack of Cinara was associated with ants, Phiedole sp. (Hymenoptera:Formicidae). This species is presumed to carry the aphid mechanically from one tree to another, to protect the aphid from natural enemies and to stimulate the sucking process.

- Some predators of the aphid were found:

Coccinelidae

Adalia bipunctata
A.10-punctata
A. shymnus

Syrphidae

Syrphus sp.

Neuroptera

Chrysophora carnea

Spiders

- None of these predators are specific to Cinara and some are parasitized.

The team concluded that:

- Chemical control of the aphids is theoretically possible but according to the socio-ecological point of view, the condition does not allow their use.

- Biological or integrated pest management methods could be more efficient for Rwanda.

MEASURES TAKEN BY THE GOVERNMENT

- Stop pruning and thinning in cypress plantations.

- Avoid systematic cutting of trees attacked by the aphids.

- Start research on species resistance and any other relevant method to control the pest.

STRATEGY FOR SHORT AND LONG TERM TO CONTROL THE APHID

- Reduce the monoculture of Cupressaceae.

- Select species according to their ecological and edaphic needs in order to increase their resistance.

- To set up a national network on cypress aphid.

- To favour information exchange between countries where the aphid is recorded.

- To control movement and transport of plant material inside as well as from outside of the country.

RESEARCH PROGRAMME (FIVE YEARS)

PHASE 1: SHORT TERM RESEARCH - TWO YEARS

Research on resistance:

- To mark and follow up of assumed resistant trees for 2-3 years. Fully resistant trees will serve for seed collection.

Progress of early attacked trees:

- Trees with different levels of attack will be followed to evaluate rates of decline and recovery.

Evaluation of secondary pests of cypress:

- Record presence of bostrichidae, curculionidae and cerambycidae in dead and dying trees.

Association with ants:

- Prevent ants from climbing into trees and aphid colonies to observe the impact of ants on the aphids.

Population dynamics and life history of Cinara:

- At regular intervals, count individuals which compose colonies and record number, % of winged and wingless forms, duration of life cycle.

Study of the behaviour of the aphid:

- Observe the movement of marked individuals.

- Study the factors influencing the appearance of winged aphids.

- Study the effect of light and temperature on the aphid.

Training of staff:

- Possible training of a forest entomologist at IIBC.

Monitoring and evaluation of local predators.

PHASE 2 - LONG TERM PROGRAMME (THREE YEARS).

Biological control (If a specific natural enemy is found)

- Field release.

- Monitoring and evaluation.

CURRENT STATUS OF APHIDS IN UGANDA: THEIR IMPACT ON FOREST RESOURCES AND CONTROL OPERATIONS THUS FAR EMPLOYED

By

Peter Kiwuso
Forest Entomologist
P.O. Box 1752
Kampala, Uganda

INTRODUCTION

Softwood plantations in Uganda cover a total of 13,381 ha. They consist of almost exclusively three main species. Pinus patula is planted on the poorer high altitude sites. Cupressus lusitanica is planted on better high altitude sites. Pinus oocarpa and P. caribea are planted on lower altitude sites. Other softwood species have been planted but form a negligible proportion. These include P. ellioti, P. taeda, Cupressus benthamii, P. kesiya, Araucaria cunninghammii and Callitris preissi.

The areas planted with each of the major species are:

Until recently, these softwood plantations were flourishing with little problem. Although with scattered attacks from lepidopterous defoliators such as Gonmeta podocarpi, Buzura edwardsi and Pachymetana sanguicincta, these forests have been relatively free of major insect problems of economic importance. This is not the case now. These softwoods, planted mainly for the provision of sawn timber, pulp, fuel and by small scale farmers as hedgerows and shelter belts are currently under heavy attack by an exotic aphid, Cinara cupressi. First observed in Malawi in 1986, this insect pest has spread up to Uganda.

PEST STATUS OF THE APHID IN UGANDA

As mentioned, the cypress aphid has attacked cypress forests and hedgerows in Uganda causing substantial damage and loss to the cypress crop.

The attack was first reported in November 1989 in Echuya Forest Reserve, Kisoro District bordering Rwanda. Since the pest had previously been reported in Rwanda, it is most likely that the pest spread from their.

From Echuya Forest Reserve, the pest has spread to all major cypress forest reserves, woodlots and hedgerows in the country.

The following cypress forests in the indicated regions have been attacked by cypress aphid:

SOUTHWESTERN REGION

The softwood plantations of Muko (162 ha), Mafuga (1386 ha) and Kiirima (926 ha) have had the heaviest toll of the aphid attack. Over 70 % of the cypress trees in many of the compartments in the area have also been infested heavily. Attack has also been reported in Rhoho (52 ha) and Bugamba (131 ha) forest reserves.

MID WESTERN REGION

The Mwenge group of softwood plantations in this area have reportedly been attacked. Those attacked are Kagorra (414 ha), Kyehara (47 ha), Kikumilo (45 ha) and Kibale (123 ha). Hedgerows and woodlots have also been attacked in the region.

CENTRAL, WESTERN AND NORTHERN REGIONS

Wampanga softwood plantation (471 ha) in the western region has been reported attacked by the aphids. Cypress hedgerows in the Central and Northern Regions have also been attacked.

NORTHWESTERN REGION

Lendu softwood plantation (1292 ha), on the border with Zaire has been reported to be as heavily infested as the softwood plantations in the Southwestern region. Usi (327 ha), Awang (94 ha) and Okavo (232 ha) forest reserves including cypress hedges and woodlots have also been heavily infested.

EASTERN REGION

Softwood plantations of Suam (793 ha) and Kapkwata (1089 ha) on the slopes of Mt. Elgon bordering Kenya are not apparently attacked. But since the presence of the aphid has been reported elsewhere, there are fears that the infestation is likely to intensify and spread like it has done in other regions of the country.

In summary, the aphid has spread to every part of the country carrying with it a trail of destruction.

IMPACT ON THE FOREST RESOURCE

As already pointed out, Uganda's softwood resource consists almost exclusively of three species; Pinus patula, Cupressus lusitanica and Pinuscaribea. Today, C. lusitanica, which accounts for 35 % of total softwoods planted, is under very serious attack from the aphid. Although the most noticeable damage is on mature trees, all other age groups are being affected and are losing vigour and drying up. This is posing a very serious threat to the afforestation programme using this species. In fact, the general public, who now refer to the infestation as "slim of cypress trees" are no longer interested in taking cypress seedlings for their private woodlots. With the death of the current stock in our forests and woodlots and the reluctance by the general public to plant more cypress, cypress stocks are going to decline seriously. This is going to cause a loss of the following benefits to our economy which would otherwise arise from the utilization of the forest resource:

- Royalty payments.

- Sales tax on sawn wood.

- Taxes on industries using this species.

- Foreign exchange earnings from the export of the resource.

- Supply of raw material to aid in the reconstruction and development in the country at a reasonable price.

In general, the future of the cypress plantations in Uganda depends on the proper management and control of this exotic pest - Cinara cupressi.

CONTROL MEASURES THUS FAR EMPLOYED

The Forest Department Research Section has tried out pesticidal methods of control. Possible chemicals were tested and their efficacy noted. The following insecticides in the following dosages were found to be effective against aphids:

Although preliminary studies carried out indicated that control with the above chemicals was possible, there has not been any spraying of the forests in Uganda.

This is because not only is the method prohibitive in terms of the cost of pesticide and application but it offers only a temporary solution. Besides, because of the nature of forests, it is generally difficult to achieve adequate coverage of pesticides in the forest canopy.

Since Cinara cupressi is an exotic pest having originated from southern Europe where the same pest is kept under control by natural enemies, classical biological control can apply here through importation and release of natural enemies.

The Forest department has this view and has embarked on biological control in conjunction with the Biological Control Unit at Kawanda Research Station.

Initial work was supposed to start with surveys and mapping of the pest problem but because of lack of necessary logistics, the work has not begun.

Otherwise our best hope lies in the biological control of this pest.

A REPORT ON CURRENT STATUS OF PINE INSECT PESTS WITH PARTICULAR REFERENCE TO PINE APHIDS IN ZAMBIA

By

O. Shakachite
Forest Pathologist/Entomologist

And

B. Chenduauka
Forester, Entomologist, Computation Specialist

Division of Forest Research
P. 0. Box 22099
Kitwe, Zambia

SUMMARY

Pine plantations are generally healthy in Zambia but this fortunate situation may not continue hence the need for continuous surveillance and observational work. Forest hygiene regimes used as a prophylactic treatment are needed to decrease the danger of Pinus plantations caused by some indigenous and potential exotic pests. No defoliators of economic importance have been found during previous surveillance done and no outbreaks have been reported in spite of large numbers of existing potential defoliating species. The climatic conditions are considered suitable for many exotic pest species. Therefore, practical quarantine systems on forest and wood products should be well established to prevent or delay the introduction of foreign forests pests. Of the potential pest species, the pine woolly aphid in particular constitutes a potential danger to Pinus plantations.

INTRODUCTION

The planting of exotic species began in Zambia on a large scale in 1963. The total area planted up to the beginning of 1991 was approximately 60,000 ha, being mainly planted with exotic pines and eucalypts throughout the country. About 50,000 ha of the plantations are for industrial and 10,000 ha are for provincial or community purposes. The rat of planting however, decreased over the past 10 years with ZAFFICO, Ltd (Zambia Forestry and Forest Industries Corporation) replanting only about 350-500 ha/a. The plantations have been established to fulfil the needs of sawn timber, fuel wood, particle board and pulp requirements in the country.

The establishment of the Entomology Section in 1974 marked the beginning of organized research work on forest pests in Zambia. Then continuous forest insect surveys started in plantations and investigations on potential pests were initiated.

The impact of insect pests on forest plantations has been more than that of diseases, hence protection of forest plantations from insect pests is very important. It is generally known that plantations in dry tropics in Africa stocked with fast growing exotic trees may become susceptible to extensive pest attack (Anon 1974). In Zambia, the number of introduced forest pests with serious impacts has been relatively small and large outbreaks of native pest insects have been uncommon,. Emphasis is therefore on preventing new pests, introduced or native, spreading and establishing themselves in plantations. This requires an effective pest surveys as well as development of strict legislative measures by quarantine and embargoes to prevent potential spread of pests through movement of plant and forest product materials, presently observed to be lax. The original spread of Phoracantha beetles, a major insect pest into the country was largely due to lack of these measures. Earlier pest surveys have shown the presence of aphids on pines and these findings are presented in some research interim reports (Loyttyniemi 1975, 1978, Ivory 1977, Selander & Bubala 1983).

DETECTION AND EVALUATION

The entomology section monitors and detects any pest, either potential or occasional, minor or major in forest plantations, and to keep up-to-date information on the general pest situation in the country. Forest pest surveys have been conducted since the early 1970's. The first general reports on the insect pest situation in forest plantations being based mainly on the findings in the Copperbelt province were those by Loyttyniemi 1975, Ivory 1977, Loyttyniemi 1980b, 1980d and Selander & Bubala 1983. Furthermore, these have been supplemented by reports made by visiting scientists.

The forest pest survey and the entomological field work in general have been the principal source of material for the establishment and enlargement of the insect reference collection. The collection provides reliably recognized insect material for the species identification of any other specimens of forest entomological interest.

The most valuable part of the insect reference collection consists of the specimens authoritatively identified by the identification service of the International Institute of Entomology British Museum, London or by other specialist in corresponding institutions. Presently, the number of insect specimens in the collection amounts to about 6,000 to include approximately 1,500 different species, mainly consisting of beetles (Coleoptera), paratype specimen new to science and several new findings to Zambia (Beaver & Loyttyniemi 1985a, b, 1989, Loyttyniemi et al. 1989).

The number of entomological records on the distribution and harmfulness of forest insects has considerably increased during the past few year's due to intensive research, survey and communication. Useful information about economically important groups of Zambian insects have become available also from other sources. In order to maintain up-to-date information on forest insects for the purposes of further research, forestry extension and publicity, use has been made of modern microcomputers by developing the forest entomological data based information system, FORENTO, for Zambian conditions (Selander & Chenduaka 1987). The system is based on the application of KNOWLEDGEMAN, the universal knowledge management system (Microdata base systems, Inc. Lafayette, Indiana, USA).

At present, FORENTO grow comprises more than 1500 entomological records from more than 50 localities (Plantations or districts). The information can now be readily used for the purpose of knowledge inquiry.

INSECT PESTS ON PINES

Pines have been grown in Zambia under plantation conditions since the early 1930's firstly in small research trials, but on a commercial scale since the early 1960's. The planted areas now exceed 40,000 ha. The main commercially grown species are Pinus kesiya Royle ex Gordon and Pinus oocarpa Schiede.

There are no major and economically important pests on pines in Zambia so far, but there are potential pests, both indigenous and introduced ones (Esjberg 1978, Van Den Berg 1979, Odendall 1980) have been considered in several contexts (Loyttyniemi 1975, 1978, Ivory 1977). On the other hand, minor and occasional pests of pines include some 25 species, both defoliators and bark borers, but their effects on growing trees have been negligible (Loyttyniemi 1980b) or very secondary (Mikkola et al 1979, Loyttyniemi 1980e, Selander & Bubala 1983).

An effect of simulated defoliation on young pines thus in the absence of any pest has been studied in order to find out how pines would recover and grow if actual damage by any potential insect defoliator would occur (Loyttyniemi, 1980f). It was found that P. kesiva and P. oocarpa can survive after complete defoliation, and that the reduction in growth may remain economically tolerable (Loyttyniemi 1981).

The monoterpene composition and tree to tree variation in the needle oil of P. kesiya, P. occarpa and P. caribea has been determined as a part of a study designed to evaluate the susceptibility of pines to pests in Zambia. The results also throw some light on the specific characters of these pine species as a potential source of commercial turpentine (Hiltunen & Loyttyniemi 1978, Loyttyniemi et al 1982).

FOLIAGE PESTS

PINE NEEDLE APHID (EULACHNUS RILEYI, WILLIAMS)

This Lachnid aphid was for the first time in any tropical region recorded in Zambia (Loyttyniemi 1979). The aphid is present sometimes abundantly in the pine plantations in the country (Selander & Bubala 1983), but its effect on tree growth has remained negligible. The aphid has been found on all Pinus species examined; P. caribea Morelet, P. merkusii De Vries, P. michoacana Martinez, P. oocarpa Schiede and P. patula Schlect & Cham. It has been found particularly abundant on P. kesiya, P. oocarpa and P. merkusii. (Fig 1.)

Fig. 1 Pine plantations infested by the pine aphid, Eulachnus rileyi in Zambia.

The life cycle of the aphid in Zambia has shown that the species continuously produces overlapping generations of apterous viviparous females, Winged females are also present at all times of the year. According to Loyttyniemi 1979, the build-up of populations is rapid around May to June after the rains had ceased, and the onset of the rains cause a drastic decrease in population density in November to December. Some Coccinellids, especially Cheilomenes sp. have been observed to have occurred abundantly and preyed on the aphid (Loyttyniemi 1979).

The aphid is known to feed on the needles, and all age classes of the needles are attacked. The infestation is easily detected in the dry season being revealed by copious honeydew. Even in the case of heavy infestation, yellowing of the foliage has only been seen in the second oldest mature needle whorl. Premature needle cast has not been observed to occur. As new growth quickly replaces the old moribund needles, the damage to trees may remain slight even if the infestation becomes more severe.

The aphid is not therefore regarded as a major pest but a potential and threat to Zambia pine plantations. The aphid was not found in the earlier surveys in 1974-1975, hence this suggests that the species may have entered Zambia and spread through the pine plantations very recently (Loyttyniemi 1979).

The aphid was identified as Eulachnus rileyi (Williams) from specimens collected from P. kesiya in Chati Plantations in the Copperbelt Province. P. rileyi has not been an important pest in its original distribution area on P. sylvestris in Nebraska (Williams 1910) although some other closely related species have caused severe damage to pines (Kearby 1967, Browne 1968, Campbell & Balderston 1971).

PINE WOOLLY APHID (Pineus pini)

It is notable that other pine aphids, like Pineus pini (Katerere 1982) in Malawi (Esbjerg 1978) in Tanzania (Odera 1974) and in Zimbabwe (Anon 1973) exist. It is probable Pineus pini will spread into Zambia in the near future or it may already exist owing to its effective anemochloric dispersion and easy transportation by man (Loyttynieme 1970). It is not possible to predict yet how sensitive Pineus pini attack to Zambia pine plantations will be, because the resistance of the Pinus species here and effect of natural control including climatic factors is not known. If this pest cannot be eradicated at an early stage of its occurrence, there must be careful consideration before very radical and expensive countermeasures are undertaken, because the experience so far is that established woolly aphid species cannot be eradicated or successfully controlled in practical forestry by technical or chemical means only.

OTHER INSECT PESTS

Bark and Stem Borers

Fresh Pinus kesiya logs and moribund fire damaged or chemically thinned trees have been occasionally attacked by pinhole boring Xyleborus species (Scolytidae) and an undermined wood boring curculionidae species. A Chysobotris species (Buprestidae) attacks the same breeding material, and this species is considered as a potential risk to stressed pines in Zambia. Some old traces of shoot borers on P. kesiya were found possibly caused by Lepidoptera pests. The European pine shoot moth Rhyacionia buoliana causing similar damage can be considered as a potential pest for pine plantations in Africa, including Zambia. The insect pest has been reported on fast growing Pinus species from the Mediterranean region and South America (Ram Reddy & Singh 1975). So far no injury in pine leaders has been found in P. kesiya.

Cone and Seed

Pine cones in forests and cones and seeds during extraction have been inspected, but no traces of seed and cone insects have been found so far. Only storage pests have been found to exist. A potential exotic pine cone pest in Zambia might be Pissodes validirostris (Curculionidae).

Pine Thrips

In Chati area slight thrips (Thysanoptera) attack has been found on Pinus kesiya needles. Thrips species Heliothrips haemorrhodalis, in South Africa is reported to have infested young pine plantations, including P. kesiya causing wilting and defoliation (Anon 1970, Took, F.G.C. 1935b).

CONTROL

Chemical control of pine insect pests has not been suggested in Zambia since no insect pest of economic importance on pine has been found and no outbreaks has been reported from previous surveys. Forest hygiene is needed to reduce the danger to Pinus plantations caused by some indigenous and exotic potential pests. Several Coccinelidae species have been found as predators of Eulachnus rileyi particularly Adonia variegata (Goeze). Cheilomenes propigua Muls., C. securinger Mader, C. sulphurea, Chilocorus distigma (Klug) Exochomus flaviventralis Mader, and Micraspis striata (f). Of these Cheilomenes sp. especially C. propigua occurred abundantly.

FUTURE PINE INSECT PEST MANAGEMENT

In general, there have not been many changes in insect pest fauna in pine plantations since the early 1970's. No large-scale outbreaks have occurred although there are several potential pests which could reach pest status in Zambia conditions. In the future, the objectives of pine insect pest management should be considered possibly under two categories. Firstly, to reduce avoidable and unnecessary losses in plantations. These objectives can be reached in the short- term if immediate actions are taken. Secondly, the goal should be to develop a long term plan on research of pine insect pests which could focus on the following:

To increase the scientific understanding of the significant biological, ecological and economic processes in the growth of pine forest plantations in Zambia, in connection with the population dynamics of potential pests and their natural enemies.

To develop alternative tactics and methods, especially silvicultural, biological and tree resistance techniques which are ecologically most compatible and still economically acceptable.

To improve methods of collecting, processing and interpreting of relevant biological and forest protection data, etc.

LITERATURE CITED

Anon, 1973. Further notes on the pine woolly aphid, Rhodesia For. Commission, Res. Newsletter No. 5-6.

Anon, 1974. Tree planting practices in African Savannas, F.A.O., Forestry Paper No. 19, Rome 185 pp.

Browne, F.G., 1968. Pests and diseases of forest plantation trees, Clarendon Press, Oxford, 1330 pp.

Campbell, R.L. & Balderston, C.P., 1971. An approach to an integrated control program for Scotch Pine Christmas trees in Ohio. J. Econ. Entomology 64, 218-223.

Esbjerg, R.L., 1978. Field handbook of Malawi forest insects. Copenhagen, Denmark. 62 pp.

Hiltunen, R. & Loyttyniemi, K. 1978. Monoterpene composition of needle oil in Pinus kesiva Royle ex Gordon. Communicationes Instituti Forestalls Fenniea 94(1) 9pp.

Ivory, M.H. 1977. Preliminary investigations of the pests of exotic forest trees in Zambia. Commonwealth Forestry Review 56:47-56.

Katerere, Y. 1982. Aphid density and animal damage to Pinus patula Schiede and deppe in a clone bank at Mesetter Forest Research Station, South African Forestry Journal 122: 63-65.

Kearby, W.H. 1977. Helicopter spraying for aphids in Scotch pine plantations. J. Econ. Entomology 60: 1453.

Loyttyniemi, K. 1975. Forest insect pests in commercial eucalyptus and pine plantations in Zambia. Division of Forest Research. Interim Report. Mimeo 24 pp.

Loyttyniemi, K. 1978. Status of pine insects in Zambia. Paper for the joint meeting of IUFRO working parties on Diseases of Tropical Pines and Pine Insects in the Tropics. Medellin, Columbia. Mimeo. 3 pp.

Loyttyniemi, K. 1979. Eulachnus rilevi (Williams) (Homoptera, Lachnidae) infesting pines in Zambia. Annales Entomologici Fennici 45:116.

Loyttyniemi, K. 1980b. A preliminary annotated list of pine insects in Zambia. Division of Forest Research. Research Note No. 26. 13 pp.

Loyytyniemi, K. 1980d. A preliminary annotated list of Eucalyptus insects in Zambia. Division of Forest Research. Research Note No. 28 19 pp.

Loyytyniemi, K. 1980e. Life history and potential harmfulness of a Buprestidae beetle on Pinus sp. Division of Forest Research. Report FE/3/1. Mimeo. 3 pp.

Loyttyniemi, K. 1981. The effect of artificial defoliation on the growth of Pinus kesiya and Pinus oocarpa in Zambia. Insect Science and Application 2: 153-155.

Loyytyniemi, K., Beaver, R.A. and Loyytyniemi, R. 1985. Annual flight patterns of timber insects in a Miombo woodland in Zambia. Platypodidae (Coleoptera). Annales Entomologici Fennici 51: 27-29.

Loyytyniemi, K., Bubala, M. and Selander, J. 19089. Forest pests and their management in Zambia. Division of Forest Research. Research Note No. 43. 23 pp.

Mikkola, L., Piearce, G.D., Loyytyniemi, K. and Mubita A.C. 1979. Late stock - scion incompatibility in Pinus merkusii De Vries in Zambia. Commonwealth Forestry Review 58: 207-2090.

Odendaal, M. 1980. Insect studies in plantations of Pinus patula in Zimbabwe, South African Forestry Journal 115: 69-71.

Odera, J.A. 1974. The incidence and host trees of the pine woolly aphid. Pineus pini (L) in East Africa. Commonwealth Forestry Review 53: 128-136.

Ram Reddy, M.A. and Singh, P. 1975. Diseases and insect pests of fast growing trees for developing countries - softwoods. Second F.A.O. Technical Consultation on Forest diseases and insects. New Delhi, India, 1975, 10 pp.

Selander, J. and Bubala, M. 19983. A survey of pest insects in forest plantations in Zambia. Division of Forest Research, Research Note No. 33. 33 pp.

Selander, J. and Chendauka, B. 1987. FORENTO: A computer based information system for the management of entomological records. Division of Forest Research. Control Plan FEO/3. Mimeo. 10 pp.

Tooke, F.G.C. 1935b. The greenhouse thrips, Heliothrips haemorrhoidalis Bouche, a pest of pines. Bull Dept. Agric. South Africa 142, 45-52.

Van Den Berg, M.A. 1979. Research on forest timber insects in South Africa since 1899. Phytopylactica 11: 69-78.

EXOTIC CONIFER APHIDS IN ZIMBABWE: STATUS AND PRESENT CONTROL STRATEGIES

By

Ramas Mazodze
Forest Entomologist
Forestry Commission, Zimbabwe

Conifers planted in Zimbabwe belong to two main genera, Pinus and Cupressus. The former is the most commercially important, now established on over 70,000 ha of plantations. Three major species are grown, Pinus patula, P. elliotti, and P. taeda and these are attacked by the two exotic (introduced) aphids, Pineus pini and Eulachnus rileyi.

Cupressus sp. are widely planted in Zimbabwe as hedges, ornamentals, windbreaks or noisebreaks and are a prominent feature of our urban landscapes. There are only a few plantations. Three major species are planted; Cupressus lusitanica, C. arizonica, and C. torulosa. The recent outbreak of Cinara cupressi caused tree dieback and deaths, and aroused a lot of public concern though many trees survived, some probably due to resistance (highly infested individuals have been observed flanking healthy ones).

Pineus pini

The pine woolly aphid was probably introduced into Zimbabwe in 1962 through P. taeda scions imported from Australia. It is now widespread through our pine plantations.

Pineus infestations in Zimbabwe, like elsewhere, result in browning of the needles, shoot dieback or tree mortality. However, in both inter- and intra-specific variation in susceptibility have been observed. Of the three commercial species, P. ellioti is the more susceptible while P. patula and P. taeda are much more tolerant.

The impact of Pineus was more severe during the first few years of its introduction than it is now. This is probably due to two main reasons.

1. Native natural enemies had to adapt to the new insect and build up their populations within the plantations over time. The coccinelid beetle (adults and larvae) are notable predators, also syrphids (larvae of hoverfly) (Katerere 1983b).
2. A tree breeding strategy started some 20 years ago has ensured that susceptible individuals of families are rogued out from the seed orchards. In fact most young plantations (less than 20 years old) are more resistant to Pineus than the older plantations were at the same age.

Although the damage due to Pineus at present is below economic threshold levels, there are no figures to support this claim and close monitoring through periodic surveillance is a continuous process. Losses of increment are obvious and certainly classical biological control integrated with natural biological control should provide long-term sustained control. Pineus is most abundant between August and September (hot, dry period).

Chemical Control - Soon after Pineus was noted, BHC was used in an attempt to eradicate it. This was a failure. Chemical control is presently not recommended. Avoidance of off-site planting and planting of less susceptible clones is being encouraged.

Eulachnus rileyi

This aphid was first noted in 1980 but the exact time of its introduction is not known. It is also very widespread and is found throughout the year though the peak populations occur between August and October.

Eulachnus causes yellow mottling of needles which at times turn yellow or brown prior to defoliation. P. patula, the most susceptible of our commercial species, is defoliated while the needles are greenish-yellow.

Eulachnus has caused unusually severe damage this year and total rainfall for the 1990/91 season was below average. This demonstrates the principles that: one, continuous pest surveillance of the plantations is necessary; and two, moisture stress predisposes the trees to attack; and thirdly, most indigenous natural enemies do not synchronize their life cycles well with exotic hosts.

The woolly aphid predators also feed on Eulachnus. Another controlling factor as reported by Katerere (1983a) is a fungus, Entomophthora planchoniana. especially under humid conditions.

Chemical Control - As for the woolly aphid, chemical control is not recommended at present and no insecticide has been used against this pest before.

Cinara cupressi

This aphid was first noted in July 1990 and the exact time of its introduction is not yet known. It is now widespread throughout the country and seems to occur only in the dry season (July to October).

The impact of this aphid aesthetically has been quite catastrophic. Variation in susceptibility among the cypresses has already been observed. C. torulosa trees have been less frequently attacked or are less susceptible that C. lusitanica and C. arizonica. No attacks have been observed in the nursery.

Chemical Control - Treatment with a systemic (Dimethoate or Metasystox) has been recommended (soil drench or full cover spray). No feedback on success/failure has been received. It appears that chemical control is a costly exercise as continuous reinfestations call for repeated treatments.

Native natural enemies have not been observed yet.

GENERAL RECOMMENDATION

Classical biological control of the three aphids by introducing natural enemies from the regions of origin is ecologically sensible and will certainly result in decreased losses of increment as well as risk. Once established, biological control should be the most cost-effective since in forestry we are dealing with fairly permanent habitats.

REFERENCES

Barnes, R.D., R.F. Jarvis, M.A. Shweppenhauser and M.J. Mullin, 1976. Introduction, spread and control of the pine woolly aphid, Pineus pini (L.) in Rhodesia. South African For. Jour., 96:1-11.

Katerere, Y., 1983. The fungus Entomophthora plachoniana Cornu (non Thaxter) parasitic on the pine needle aphid, Eulachnus rileyii (Williams) in Zimbabwe. (unpublished).

Katerere, Y., 1983. Insect pests of pine plantations in the eastern districts of Zimbabwe. Zimb. J. Agric. Res. 21:101-105.

Mazodze, R., 1990. A review of forest entomology in Zimbabwe. Prepared for the Forest Research Seminar - "Forest Research Advances in Zimbabwe" held in August, 1990, Mutare, Zimbabwe.

Mazodze, R., 1991. Outbreak of the cypress aphid, Cinara cupressi in Zimbabwe. Prepared for a talk to the Harare City Rotary Club, 12 March, 1991, Harare, Zimbabwe.

Mills, N.J. 1990. Biological control of forest aphid pests in Africa. Bulletin of Entomological Research 80:31-36.

Odenaal, M., 1980. Eulachnus rileyi (Williams) (Aphididae:Lachininae): a new pest of pines in Zimbabwe. South African Forestry Journal, 115:69-71.

Piearce, G.D., 1990. The cypress aphid outbreak. Forest Research Newsletter, 2 (4).