0149-B1

Protection of the Lebanese Cedar Forests with Particular Emphasis on the New Pest Cephalcia Tannourinensis N.Sp

Ghattas Akl, Fady Asmar^[1], Michel Bassil, Zeina Tamim, Nasri Kawar and Nabil Nemer

Abstract

One of the largest cedar forests in Lebanon, the Cedar Forest of Tannourine, is severely infested by a wood-wasp, recently identified as Cephalcia tannourinensis. The insect outbreak threatens all the cedar forests in Lebanon and the region. The paper describes the campaign to control the pest. Specific surveys for monitoring the Cephalcia population were developed and other insects were also found on the cedars.

Since 1999, the yearly spraying operations undertaken to control the insect outbreak have shown good results. The populations of the different insects will be regularly monitored for the preparation of an integrated pest management system in the cedar forests of Lebanon.

The monitoring of the insect populations and the control of the Cephalcia tannourinensis will contribute to the efforts of protection and rehabilitation of the cedar forests in Lebanon.

Introduction

Since ancient times, the overexploitation of the Lebanese Cedar has resulted in the depletion of most of the mountains of Lebanon leaving only a few scattered stands. Despite their low density, Cedars of Lebanon are of importance in genetic diversity of the species, and constitute the southernmost cedar population. The long history of cedars and people in the region forged a strong cultural link between this tree and the people. Thanks to legends and tradition, the cedar forests were not completely depleted.

One of the largest Cedar Forests in Lebanon, Tannourine, (1,600 to 1,850m altitude), is severely infested by a new wood-wasp species, recently identified as Cephalcia tannourinensis. The whole stand is attacked and the pest is spreading, threatening the surrounding forests, including the "Forest of the Cedars of God" in Bcharreh (1,804 to 2,057m) registered in the World Heritage Convention. The neighboring countries are also under threat and are concerned about the possible trans-boundary spread of the insect.

The protection of the cedars in Lebanon from Cephalcia tannourinensis contributes to the protection of Cedrus libani populations around the world and especially in the neighboring countries.

The Rural Development and Natural Resources Directorate (RDNRD) at the Lebanese Ministry of Agriculture (MOA) initiated a joint venture with the American University of Beirut (AUB) and with experts from the Institut National de la Recherche Agronomique, INRA-France. The MOA provided funds for four aerial spray operations. A Technical Cooperation Project (TCP) with the FAO provided the necessary assistance for further studies.

(Asmar 2000, and FAO 2001).

Materials and Methods

Inventory of cedar insects

The pitfall traps were used for the inventory of the insect populations. Five plots, about 50 m apart, in each of Tannourine and Hadath El Jebbeh, were established along a transect line into the forest. Within each plot, five pitfall traps were placed. Traps installation was completed in October 2001 and each trapping period lasted for one week. Samples collected from each pitfall are sorted to the order, family and species levels.

In addition to Cephalcia tannourinensis, other insects were found.

Monitoring Cephalcia tannourinensis population in Tannourine-Hadath El-Jebbeh

The surveys are conducted for evaluation of Cephalcia populations, estimation of the depredation. Pest control evaluation are conducted to evaluate treatment.

Pest population assessment

Tannourine Hadath El-Jebbeh is divided into four zones: Tannourine; Arz el Kourssi; Hadath El- Jebbeh; Qnat

A total of 30 sample points (40cm x 40cm) are taken from the four zones in the following patern: Tannourine (10); Arz El Kourssi (10); Hadeth El- Jebbeh (5); Qnat (5). Soil samples at a depth of 40cm are taken for counting all larvae present. The larvae are divided into those that would emerge in 2002 and those that would stay in diapause. These surveys are conducted during October, November, December, April and May and are the basis for predicting population levels at adult emergence time during spring and for evaluating the need for suppression interventions. Yellow sticky traps in the soil-sampled sites are used to monitor adult emergence during the spring.

Pest control evaluations are conducted after the aerial spraying to appraise the efficacy and/or safety of the treatment using the following procedures:

1. Egg sampling, during one month depending on the emergence of adults and weather conditions. This method is also an indicator of buds damage assessment in case no intervention is taken. It consists of collecting branches (length: 20cm) randomly, every seven days, from 50 sampling points in Tannourine Hadath-El Jebbeh.

2. The impact of Cephalcia on cedars is measured collecting branches from 50 random sampling points during the months of larval development and then after the larvae drop i.e. May, June, July and August. The number of attacked buds, the length of new bud growth and other tree growth development criteria are recorded. This method will estimate the amount of depredation resulting from insect feeding activity during spring.

The sampling of the underground larvae have shown to be the most reliable method for estimating Cephalcia population since it takes into account the diapausing population.

Spraying Operations

The treatment tactic used is an insect growth regulator, acting on the population of Cephalcia. Once the high population of the pest is suppressed, other treatment tactics could be used.

After considering the first biological studies on the new insect pest Cephalcia tannourinensis, the use of the insect growth regulator, diflubenzuron known as DIMILIN SC 48 was chosen and one outbreak area was considered: Tannourine Haddet El-Jobbe (FAO, 1993).

Products and method of application

Dimilin SC 48® was mixed with the oil adjuvant, Citrole^®. The products were chosen for their ability to be used in the ultra-low volume (ULV) method of spraying.

Considering the geography of the mountain and the lack of equipment, a helicopter Alouette II from a French company (procoptere), equipped with a full ULV pulverization system with wind driven nozzles was imperative for a treatment of 3L/hectare in the years 1999 and 2000 (Démolin et al 2001) and (Nemer et al 2001). In 2001, a Bell 205 helicopter form the Lebanese Army equipped with a Simplex pulverization system with electric nozzles supplied by Micronair was used. Dimilin SC 48 was used at the rate of 75 g a.i./hectare (0.165 L/hectare) mixed with the Citrole^® at a rate of 1L/hectare. Water was added to make up the rate of 3L/hectare. The spraying took place on June 11-13, 1999, June 16-18, 2000, May 22-24, 2001 and May 22-24, 2002.

Sampling procedures

Soil samples

20 sampling points were chosen inside the sprayed and unsprayed area (about 200 hectares, elevation range 1600-1800). At each point, a soil sample of 40x40x50 cm was taken within the crown projection of the trees. The sampling was done once/month, from September 1998 to March 2001, in a total of 36 sampling sessions. The number of pre-pupae extracted from the soil was recorded for each month (Nemer et al 2001).

Yellow traps

In mid April 2000 and in early April 2001, yellow traps were set in the sprayed and unsprayed areas. The traps were suspended on a branch at about 2m above the ground. All traps were exposed for approximately 45 days and removed a few days after the end of adult emergence. The number of adults caught was recorded every four days (Nemer et al 2001)

Larval mortality

Initial observation was done two days before the spraying in 1999, 2000 and 2001 and fourteen days after the spraying in 1999; six, ten and fourteen days after spraying in 2000 and 2001. Twenty branches (25 cm) were picked randomly from the cedar trees at each point. The number of eggs, live and dead larvae for each stage were recorded (Nemer et al 2001).

Results and Discussion

Identified insects:

1. Ernobius sp. Order Coleoptera, Family Anobidae. Detected on the summer buds of cedars in 1998, it is recent in the cedar forests of Lebanon.

2. Dasineura cedri. Order Diptera, Family Cecidomyidae. Detected on the summer buds of cedars in 1999, it is also recent in Lebanon.

3. Dichelia (Parasyndemis) cedricola Diakonoff The Cedar Shoot Moth. In 1973, an insect infestation on the cedars of Barouk and Masser El-Shouf was reported. Larvae were feeding on the cedar needles and buds. The adult moths that emerged in June-July were identified as a new species Parasyndemis cedricola, Order Lepidoptera, Family Tortricidae. Recently, the genus name was changed to Dichelia. The insect was not reported in other cedar forests. In the course of studying the biology and life cycle of D. cedricola, four Hymenopterous parasites of the larvae were found. These were identified as follows: Microdus sp. (Hymenoptera, Braconidae); Dusona sp. (Hymenoptera, Ichneumonidae); Scambus sp. (Hymenoptera, Ichneumonidae); Scambus elegans (Hymenoptera, Icneumonidae). The four parasite species are active and help in reducing the insect population.

4. Thaumetopoea libanotica. The Lebanese cedar processionary moth, is an important insect on cedars in Lebanon. A pheromone specific for Thaumetopoea bojeani synthesized at INRA was tested in Tannourine-Hadath El-Jebbeh and Bcharreh. Delta traps containing the pheromone were placed in a number of locations in the two forests to catch adult moths. Although timing was not optimal, traps caught few adult moths of Thaumetopoea libanotica in the Bcharreh forest but did not catch any adults in the Tannourine-Hadath El- Jebbeh forest. The traps will be tried again during summer 2002.

5. Two aphid species were also found on cedars in Lebanon. They are:

• Cinara cedri in Tannourine-Hadath El-Jebbeh and Bcharreh.

• Cedrobium laportei in Bcharreh.

6. Cephalcia tannourinensis n.sp. Order Hymenoptera, Family Pamphilidae The cedar web-spinning saw-fly must have been present on the cedars of Tannourine-Hadath El-Jebbeh for several years before its damage started to intensify in 1998. It has caused large outbreaks in Tannourine-Hadeth El Jobbe in the last decades. It is an extremely voracious insect, which cause the death of the trees (Demolin et Nemer 2001).

• Description: The adult has a 7 to 11 mm flattened body. The head is large, with long antennae composed of 27-29 segments, the third segment being as long as the next two together. The wings are narrow, transparent with dark venation, light gray at the tips and cover the abdomen when folded. The wingspan of females is 22 to 27 mm and that of males is 20 to 24 mm.

  Eggs are almost cylindrical, but ovoid at both ends. Freshly laid eggs are pale yellow, 1.6 mm by 0.7 mm in size, but reach 2.3 mm by 1.1 mm before hatching and become dark yellow.

  The larva has three pairs of thoracic legs, and a pair of anal prolegs on the last segment of its body. The prevailing larva color is green. A fully-grown larva is dark green. Large mature larvae are females, smaller ones are males.

  The pupa is free and greenish. The eighth segment in a female carries rudiments of an ovipositor.

• Life Cycle: The adults swarm from mid April to mid-June. Females stick up to 7 eggs on the needles of a new bud. Each female can lay up to 50 eggs. Hatching is completed in two to four weeks. The larvae spin their webs into the bud bases. Feeding and development of the larvae lasts six to eight weeks and the larvae pass through three instars. After the last molt, the larvae cease to spin, between late June till and the end of July, drop to the ground and penetrate the mull, often to the boundary of mineral soil at a depth of 15-50 cm where they make a hole for hibernation. The end of diapause is indicated by a clarification of the larval eyes followed by the formation of large, dark and sharply delineated pupal eyes. The duration of pupation is not determined yet. A five year diapausing period was recorded for some insects within the same genus (Gruppe, 1996).

• Damage: The larvae feed on the new cedar needles and thus cause extensive damage. Attacked trees turn brown in color and look as if fire has swept through the forest.

In 1998 and 1999, 70% and 80% attack was recorded through a random sample of branches from 60 trees. Outbreaks can be predicted by counting diapausing larvae in the soil. 650 larvae/m² were recorded in December 1998 and 950 in 1999. The potential for devastating outbreaks is thus a real threat.

Results of Spraying Campaigns against Cephalcia tannourinensis n.sp.

1999

The first spraying gave good results, since more than 80% of the larvae on the trees were killed. However, due to technical difficulties the spraying operation was delayed for about two weeks and the larvae that had already dropped to the soil were not killed (Demolin et al 2001) and (Nemer et al 2001).

Population counts of underground larvae were significantly lower (50%) in the sprayed areas compared to the control plots taking into account that 35% of the larvae did not emerge during the flight period of the year 1999 (Table 1).

Adult catches on yellow traps during the April-May were significantly lower in the sprayed area than the unsprayed plots indicating the relative success of the operation carried in 1999 (table 2).

Results of the first spraying operation indicated a high mortality percentage among the first and second larval instars of Cephalcia tannourinensis, fourteen days after treatment (table 3).

2000

The treatment was successful in terms of timing and efficiency and 70-85% of the larvae on the trees were killed. The successful effect of the operation carried during 2000 was positively affected by the cold winter and resulted in a high percent mortality among first and second larval instars (table 1). The numbers of adults caught on yellow traps during April-May 2001 were less in the treated area compared to the unsprayed plots (table 2). Population counts of underground larvae were significantly lower (70%) in the sprayed areas compared to the control plots knowing that only 50% of the larvae emerged during the flight period of 2000 (table 3) (Demolin et al 2001) and (Nemer et al 2001).

2001

The Bell 205 exhibited comparable results to the operations carried by the Alouette II. Results showed a high percent mortality among the first and second larval instars (table 1). The efficacy of the treatment will be assessed through the population counts of underground larvae during the coming months and by adult catches during the flight period in Spring 2002.

Table 1. Efficacy of forest spraying on the larval instars of C. tannourinensis n.sp. in 1999, 2000 and 2001.

Table 2. Adult catches by yellow traps during the years 2000 and 2001

Table 3. Population counts of underground larva before and after the spraying during the years 2000 and 2001

Conclusion

The Cephalcia tannourinensis n.sp should be given the appropriate regional and international attention. The damages caused by this pest could be very harmful to a whole population of cedars. The control methods tested by the RDNRD, with the scientific partners aim at keeping the pest population under control, thus avoiding a wide spread of the attack.

IN addition to causing death of the insects Dimilin SC48 has metatoxic effect. That is why in the forests subject to spraying, investigations will be carried out to determine the instar and male/female structure of populations, their reproductive potential and bio-mass.

Such a complex approach to analyzing pest populations, will give possibility to forecast the development of the populations for next years with high degree of accuracy.

On the other hand, dendrochronological will be undertaken to study the history of previous insect attacks and their correlation to environmental conditions.

The application of sound sustainable management plans and appropriate conservation measures will certainly help in the attenuation of the insect attack and will contribute to the prevention of further insect outbreaks.

References

Asmar F., 2000. Ecology, Conservation and Genetic Variability of the Lebanese Cedar, M.Sc. Thesis, MAICh, Greece.

Demolin G., 1999. The Cedars of Tannourine endangered. Agrotica 30, pages10-11.

Demolin, G., N. Kawar, L. Kfoury, N. Nemer, B. Frerot and E. Abou-Fakhr Hammad. 2001. Etude d’un complexe de nouveaux insects ravageurs et dévastateurs en cédraies libanises. Rapport Intermédiaire, 99Egrn F 42/L39, CEDRE, National Council for Scientific Research (CNRS), Lebanon.

Demolin, G. and N. Nemer. 2001. Biologie des insects ravageurs, encore inconnus au niveau mondial, découverts en cédraie de Tannourine. Le 3ième Séminaire sur l’Etat d’Avancement des Projets de Recherche. Comité Franco-Libanais du Programme CEDRE, CNRS, Lebanon, 6-7 June, 2001.

FAO, 2001. TCP/LEB/0169, Protection of the Forests with Particular Emphasis on the New Pest Cephalcia tannourinensis Infesting Lebanon Cedars.

FAO, 1993. Mission Report in Lebanon. Technical Cooperation Program TCP/LEB/2251.

Gruppe, A. 1996. Model of the importance of exogenic factors influencing the variable dormancy of prepupae of Cephalcia abietis (Hymenoptera: Symphyta: Pamphiliidae). Entomologia Generalis 21(1-2), pages 95-105.

Kawar, N. 2001, Insect Pest of Cedar Forests in Lebanon. FAO project TCP/LEB/0169

Nemer, N., G. Demolin, N.S. Kawar, L. Kfoury, E. Sfeir and E. Zakhour. 2001. Forest application of benzyl-urea insecticides and effect of different chemical treatments against the Lebanese cedar web spinning saw-fly, Cephalcia tannourinensis n.sp. (submitted to Forest Ecology and Management).