 FO:TCP/RAF/4451 TECHNICAL COOPERATION PROGRAMME ASSISTANCE FOR THE
MANAGEMENT OF KENYA AND THE UNITED REPUBLIC OF TANZANIA
Terminal Statement prepared for the participating governments by the Food and Agriculture Organization of the United Nations Rome, 1998 |
Table of Contents
1, INTRODUCTION
1,1, Project background
1.2. Outline of official arrangements
2.2. Assistance in obtaining clearance
2.3. Import of natural enemies
2.4. Rearing and release of natural enemies
2.5 Impact studies
2.6 Methodology
2.7 Results in Kenya
2.9 Training
1. INTRODUCTION
Leucaena (Leucaena leucocephala) is a fast growing, nitrogen-fixing tree native to Mexico and Central America, which has been widely planted in countries such as Kenya, Malawi, Tanzania and the Sudan owing to its many desirable properties. Leucaena foliage is a highly nutritious fodder, its new shoots are eaten as a fresh vegetable, and its excellent wood properties make it highly desired as pulpwood and fuel and as a building material. Intercropping of leucaena with maize has also proved to be an excellent means of restoring soil nitrogen.
Leucaena plantings are now threatened by an exotic insect, the leucaena psyllid (Heteropsylla cubana), native to Mexico, Central America, the Caribbean Islands and South America. Between 1985 and 1988, infestations were detected in the Pacific Islands, Australia, South-East Asia and the Indian subcontinent. In late 1992, the presence of leucaena psyllid was confirmed in three African countries: Kenya, Madagascar and Tanzania. At the time of the project's inception, in 1994, the insect posed an immediate threat to leucaena throughout the African continent.
In view of the economic importance of leucaena, and the threat being posed to its continued use in East Africa, the Governments of Kenya and Tanzania requested FAO assistance under the Technical Cooperation Programme (TCP) to take plant protection measures against leucaena psyllid.
1.2 Outline of official arrangements
The Project Agreement between the CAB International Institute of Biological Control (CABI), FAO and the Governments of Kenya and Tanzania, for project TCP/RAF/4451 "Assistance for the Management of Leucaena Psyllid", was approved on 15 July 1994. The project became operational immediately and was scheduled to continue until June 1995. Field activities in fact ceased at the end of May 1996. Donor funding for the project amounted to $US 271 000. The Ministry of Environment and Natural Resources of Kenya, and the Ministry of Tourism, Natural Resources and Environment of Tanzania were the government agencies responsible for project execution.
The implementing agency for Tanzania was the Tanzania Forestry Research Institute (TAFORI), which appointed the National Project Coordinator (NPC) from the Sokoine University of Agriculture (SUA). In Kenya, the NPC was from the Forest Health Management Centre (FHMC), in the Ministry of Environment and Natural Resources. In March 1995 the NPC requested that CABI collaborate in implementing the biological control work with the Kenya Forestry Research Institute (KEFRI), part of the Ministry of Research, Technical Training and Technology.
Additional collaborators were the Tanzania Agricultural Research Organisation (TARO), the Kenya Agricultural Research Institute (KARI) and the International Centre for Research in Agroforestry (ICRAF).
The long-term objectives of the project were to raise awareness of the leucaena psyllid and the damage it can cause in order to contribute to early detection of infestations; to implement a regional strategy for managing this insect using principles of integrated pest management (IPM) and design a long-term IPM programme; to strengthen networks among African countries affected by this insect through a process of Technical Co-operation among Developing Countries (TCDC) and, finally, to encourage contacts with countries affected by this insect in the Asia-Pacific Region.
The immediate objectives of the project were: in Phase I, to prepare information leaflets and related materials, conduct sub-regional workshops and establish an information network to facilitate pooling of information, biological materials and expertise; in Phase II, to conduct surveys of infestations, carry out seasonal evaluations monitoring the population dynamics of leucaena psyllid, and prepare maps showing locations of leucaena plantings and damage caused by the psyllid; and, in Phase III, to introduce, screen and evaluate natural enemies of leucaena psyllid for use in biological control programmes, establish test plantings with proven resistance or tolerance to feeding injury by the insect, and design an integrated pest management action plan.
Existing facilities in Kenya and Tanzania which could house laboratories for rearing the Heteropsylla cubana, a natural enemy of the leucaena psyllid, were surveyed, and designs for modifying existing facilities were drawn up.
An appropriate site for an insectary in Kenya was found to be the KEFRI station at Gedi on the coast. No buildings there were considered suitable, and a new insectary was therefore proposed.
In Tanzania, likewise, the TAFORI centre in Kibaha was identified as the most suitable location and a preliminary design for a small new structure was submitted in May 1995.
2.2 Assistance in obtaining clearance
In compliance with the Project Agreement, technical assistance was provided to national programmes for obtaining social clearance for the importation of natural enemies of leucaena psyllid.
2.2.1 Selection of agents
In Asia and the Pacific, two coccinellid predators, Curinus coeruleus Mulsant and Olla v-nigrum Mulsant, and two hymenopterous parasitoids, Psyllaephagus yaseeni Noyes and Tamarixia leucaenae Boucek, had been used in biological control programmes. The predators are generalists while the parasitoids are host specific to a small number of psyllids. Tamarixia leucaenae and Psyllaephagus yaseeni were therefore selected for the first introductions, as parasitoids were likely to be more effective and safer than predators.
2.2.2 Kenya
All imports and releases of biological control agents to Kenya were subject to the approval of the Kenya Standing Technical Committee on Imports and Exports (KSTCIE), which only meets at irregular intervals. Permission for direct release was refused, but permission was granted to import the insects and release them after one generation in quarantine in the UK. At a KSTCIE meeting on 3 October 1995, it was agreed that the quarantine could take place at the CABI Kenya station instead of in the UK. The import permits were dated 29 November 1995, and were valid for six months.
2.2.3 Tanzania
In Tanzania, all requests to import biological control agents required approval by the National Plant Protection Advisory Committee. A request to import the parasitoids to Tanzania was presented in August 1993 and, after a long period of discussion concerning the conditions under which the permit could be issued, and particularly the need to monitor the results of the introductions, a permit was issued to TAFORI on 14 March 1995, and was sent to CABI on 5 May 1995. This permit gave permission for the import and direct release of the natural enemies following appropriate inspection by a Ministry of Agriculture quarantine officer.
2.3 Import of natural enemies
Shipments of the natural enemies of the leucaena psyllid, Heteropsylla cubana, into Tanzania and Kenya all originated at the CABI Trinidad station, where cultures were established from field-collected material. They were first sent to the CABI UK station, where they were screened for contaminants, washed in sodium hypochlorite, and then repackaged and dispatched to East Africa. Three shipments were forwarded to Tanzania and three to Kenya. The survival rate of the insects was generally acceptable, given the length of the journey and the extra handling that took place in the UK.
All live adults from the shipments to Tanzania were released in the field, following the required inspection by the quarantine officer from the Ministry of Agriculture. The shipments to Kenya were received into the quarantine facility at CABI Muguga, as required by the KSTCIE permit, where the insects were reared for at least one generation prior to release.
2.4 Rearing and release of natural enemies
No facilities for rearing natural enemies were available in collaborating institutes in Tanzania or Kenya. This necessitated the growing of potted Leucaena leucocephala seedlings, and the culturing of leucaena psyllids. The methods used were based on those developed at CABI Trinidad, where psyllid and natural enemy rearing was undertaken to provide the biological control agents for shipping to Africa.
In Tanzania, voucher specimens of released insects were lodged with the Ministry of Agriculture, and further specimens were retained by TAFORI. In Kenya, voucher specimens were lodged with the National Museums of Kenya.
A total of 2 075 Tamarixia leucaenae, and 1 263 Psyllaephagus yaseeni was released. Releases were made by introducing adults into muslin cages holding heavily infested branches of leucaena. Adult parasitoids were carefully introduced into the cage by holding the open vials containing the insects under the netting and allowing them to fly out. This method of release was used to provide some protection for the parasitoids, and to assist them with host location. A few days later the cages were removed.
2.5 Impact studies
The impact of introduced natural enemies can be assessed in a number of ways. One is to compare the magnitude of the pest population in the absence and presence of the natural enemy. This can be achieved by monitoring before and after the introduction of the natural enemy, or monitoring two sites simultaneously, one with and the other without the natural enemy. In this project the latter approach was recommended as being suitable to the project timescale. The sites must be separated by enough distance to prevent immediate immigration of natural enemies from neighbouring sites, but close enough to experience similar weather conditions. A distance of around 20 km was considered adequate.
Assistance was given to national programmes in setting up the sites and in training field staff to undertake the monitoring. The data collected were reported in the national programme reports.
2.6 Methodology
Leucaena can be cultivated in various ways: as hedgerows, trees and coppiced stumps. The habitat unit used for sampling was 50 cm of hedgerow, a single branch, and the whole of a coppiced stump, respectively. Non-destructive and destructive sampling methods were tested. For both methods, at each sample plot a number of habitat units were selected at random and marked for regular monitoring. The life cycle of the psyllid is such that numbers can sometimes change rapidly, and so a sampling frequency of once every 2 weeks was preferred.
2.6.1 Non-destructive sampling
At each sample occasion, and for each habitat unit, the following information was recorded: the number and identity of predators, the total number of shoots, and whether there were any inflorescences or seed pods. This information indicated the growth stage of the host plant, which affects the population dynamics of the pest. For each of the trees or coppiced stumps, the overall tree damage was observed, using the scale widely used in Asia and elsewhere (Wheeler, 1988):
1. No damage
2. Slight curling of leaves
3. Tips and leaves curling
4. Tips and leaves curling, covered with sap
5. Loss of up to 25% of young leaves
6. Loss of 26-50% of young leaves
7. Loss of 51-75% of young leaves
8. Loss of 76-100% of young leaves, blackening of lower leaves
9. Total leaf loss, blackened stem
In five shoots selected at random, or starting from the tip of the branch when sampling from trees, the health of each shoot was recorded. For the same shoots, an estimate of the number of nymphs present was made, using the following categories:
0. None present
1. 1 - 5 (assume mean 3)
2. 6 - 30 (assume mean 18)
3. 31 - 100 (assume mean 65.5)
4. > 100 on leaves only (assume mean 100)
5. > 100 aggregations extending to the stem (assume mean 100)
For the same shoots, and the three leaves below each shoot, the presence or absence of any mummies (parasitized psyllids) was also recorded.
2.6.2 Destructive sampling
At each sampling, samples were selected at random from habitat units, if possible avoiding the units used in the non-destructive sampling. Shoots were selected at random, and carefully removed into a vial or polythene bag. The next three leaves below the shoot were also removed, but kept separate.
In the laboratory, a microscope was used to score the number of nymphs and parasitoids on each shoot and associated lower three leaves. Psyllid nymphs were recorded as small (instars 1 and 2), medium (instars 3 and 4), or large (instar 5 with wing pads). The number of mummified psyllids was recorded for each parasitoid.
2.7 Results in Kenya
Field visits were made with KEFRI to identify field sites for release and monitoring of biological control agents, and to train technical staff to undertake the regular monitoring. Suitable sites and collaborators were identified at Mtwapa (KARI regional research centre), Embu (KARI/ICRAF agroforestry project), and Maseno (KEFRI/ICRAF/KARI).
In addition to the sites identified and established by KEFRI, CABI undertook monitoring at the ICRAF station at Machakos where the first releases in Kenya were made. After initial trial sampling, six shoots per hedge were sampled destructively, giving a sample size of 66 shoots once every 2 weeks. The mean number of nymphs per shoot obtained by destructive sampling showed two peaks in January and April. As would be expected, the most damage to shoots was observed in January, when pest populations were highest. On one sample occasion, over 90% of shoots were recorded as either severely damaged or dead.
Releases of bio-control agents were made at Machakos from late December 1995 to mid-February 1996. By March, the parasitized psyllids (mummies) were detected in the regular sampling. The parasitism index for Psyllaephagus was similar to that reported in Asia and the Pacific, where the insect had been released in many countries. Tamarixia had not been successfully released previously, so it is significant to note that the parasitism index rose to over 35% within five months of release. Coupled with the evidence that it dispersed well, the indications were that Tamarixia was a more effective agent than Psyllaephagus.
2.8 Results in Tanzania
Three locations where leucaena is grown, Tanga, Morogoro and Tabora, were identified as suitable for releases and monitoring. At Tabora the ICRAF/TARO agroforestry project expressed a wish to collaborate on the project, as it had already been investigating host plant resistance to the psyllid. Its data allowed a comparison to be made of psyllid populations before and after the introduction of natural enemies.
At Morogoro there had been little rain, so there was no flourishing leucaena, and very few psyllids. Consequently no Tamarixia were observed. However, subsequent observations showed that Tamarixia had spread several kilometres from the release site. At Tanga there was good evidence of initial establishment by November 1995, and evidence of parasitism by Tamarixia was found up to 10 km from the release site. Later reports indicated that Tamarixia had spread considerable distances. They were reported on the Kenya coast, north of Mombasa, prior to any releases being made there, and it was considered likely that this was a result of dispersal from the Tanga release site. There was thus good evidence that Tamarixia was firmly established in Tanzania.
2.9 Training
In Kenya, a KEFRI technician was attached to CABI for 10 weeks for bench training on rearing and sampling H. cubana and its natural enemies. During the field visits to identify and set up field sites for the release and monitoring of natural enemies, training was given to technical staff from the collaborating institutes. Training in monitoring psyllid populations, release of natural enemies, and natural enemy monitoring was provided for Tanzanian staff during visits by project scientists to Tanzania.
A training course was held at CABI, Kenya, from 4 to 8 March 1996, covering all aspects of classical biological control of the leucaena psyllid. The course comprised lectures, and laboratory and field practicals.
The significant achievements in the release and establishment of biological control agents at a limited number of sites in Kenya and Tanzania indicate that further work would be worthwhile.
The impact of the biological control agents should be monitored more closely in order to determine their dispersal, their effect on the pest and the damage they cause. It is impossible to conduct an adequate assessment within a short project, although the results of such an assessment are vital in determining the need, if any, for further intervention. This might include the redistribution of the bio-control agents to areas where they have not dispersed naturally.
As the pest has already spread to many other countries in eastern, central and southern Africa, it is proposed that the biological control agents be introduced to those countries, with appropriate monitoring and assessment.
In future research, field sampling should consist of scoring predators, plant growth and damage. For accurate population data, however, destructive sampling is recommended, as the time required in the field can be reduced. Samples must be taken directly to the laboratory in a cool box and examined using a microscope. The trapping of adults, using sticky yellow traps, is not essential but would provide information that is not available using the other methods.