IOBC wprs Bulletin Vol 22(9), 1999

Studies on the response of the leopard moth, Zeuzera pyrina L. (Lepidoptera:Cossidae) to pheromones in apple orchards

George E. Haniotakis, Athanasios Koutroubas1, Anastasia Sachinoglou1 and Aimilia Lahlou2

Abstract: Prototype pheromone dispensers prepared by TNO, The Netherlands, for monitoring and mass trapping of Zeuzera pyrina L. with different concentrations and release rates, were compared to the following commercial dispensers: a) IPO-DLO of Plant Protection Research Institute, Wageningen, The Netherlands in 1995; b) Z.p.-13505, Serbios, Italy in 1996; and c) Z.p.-01607, Serbios in 1997, in tests conducted in apple orchards in Greece. The dispenser Z.p.-01607 containing 1.03 mg of E2,Z13-C18Ac+0.075 mg of E3,Z13-C18Ac, was found superior by far to all other types prototype or commercial. Moths responded to the pheromone traps flied toward it, landed on a near-by object and enter the trap by walking. The mass trapping method with the use of prototype dispensers in Serbios traps, at a density of 10 traps/ha (in tests of 1995) or 9 traps/ha (in tests of 1996 and 1997), was not effective. The mating disruption method with prototype dispensers, each containing 100 mg of E2,Z13-C18Ac, used at a density of 446 dispensers/ha + 130 dispensers/ha containing 150 mg of the same compound (total 576 dispensers/ha), or 64.1 g of pheromone/ha, appeared to be effective in the tests of 1997. In 1998 the mating disruption tests continue using the dispenser of TNO with 150 mg pheromone content (above) at a density of 494 dispensers/ha, or 74 g of pheromone/ha. The preliminary results (tests will finish in November, 1998) are encouraging.

Key words: Pheromone dispensers, Mass trapping, Mating disruption, Zeuzera pyrina Cossidae, Lepidoptera

Introduction

The leopard moth, Zeuzera pyrina, L. is a serious pest of apple orchards in Greece. Females deposit their egg masses on the brunches of apple trees and newly hatched larvae (first instar) bore into the wood of young shoos killing them. Larvae of consecutive stages descent to lower, thicker, brunches ending to the tree trunk causing the death of parts or the entire tree depending on the level of infestation. Current control practices include either manual killing of larvae inside their galleries by introducing a flexible wire into it, a time consuming, labor intensive and therefore costly procedure, or wide spectrum insecticide applications against adults. Due to the prolonged adult emergence period, however, and the short residual activity of the insecticide sprays, a large number of applications is required throughout the active period of the insect (about three to four months) for an effective control, resulting in all known undesired side effects of such applications.

Alternative control methods have been sought for decades without acceptable practical results: Entomopathogenic fungi and bacteria, both natural and commercial, including Bacillus thuringiensis (Myers 1988; Nashnosh et al. 1993; Pasqualini 1989), insectivorous nematodes (Abdel-Kawy et al. 1992), chitin synthesis inhibitors (Myers 1988) and pheromones (Nashnosh et al. 1993; Pasqualini 1989, Pasqualini et al. 1992; Pasqualini et al. 1993) are the most extensively methods studied during the last few years.

Application of pheromones for monitoring adult populations is already being used by government agencies and apple-growers in Greece for timing insecticide applications. Their use for direct control by means of mass trapping or mating disruption appear to be at the present time the most promising alternative methods but more efficient pheromone formulations and refinement of control methods are still required. In the framework of a E.U. project (AIR3-CT94. 1607) with the title "versatile controlled release dispenser for mating disruption with pheromones" new type of dispensers based on advanced polymer technology have been developed and tested for monitoring and control of Z. pyrina L. and Cossus cossus. The results of these tests on Z. pyrina in Greek apple orchards conducted during the last four years are presented here. The results of the tests on C. cossus were not satisfactory and are not included. Greek C. cossus does not respond to pheromone blends developed for C. cossus of Italy probablu because Greek populations constitute a different strain utilizing a different pheromone blend for sex communication.

Material and methods

Experimental orchards

All tests were conducted in 2ha plots replicated three times for dispenser evaluation and mass trapping and two times for mating disruption.

Pheromone traps

Funnel-type, pyramid-shaped traps of white polypropylene (Serbios, Italy) were used in all experiments. Traps, with the pyramid basis up, were placed on poles 50 - 100 cm above the tree canopy.

Pheromone dispensers

Prototype dispensers prepared by TNO, The Netherlands were compared with commercial dispensers as follows:

Dispensers for mating disruption

1997 (576 dispensers/ha)		1998 (494 dispensers/ha)
Code No.	Content	Code No.	Content
Z.P.-112D	100mgE2	Z.P.-114	150mgE2
Z.P.-114	150mgE2

Dispensers for monitoring and /or mass trapping.

1995 (20 dispensers/ha)		1996 (18 dispensers/ha)		1997 (18 dispensers/ha)
Code No.	Content	Code No.	Content	Code No.	Content
1804-1a	4.75 mg E2* + 0.25 mg E3*	2703-10	9.0 mg E2 + 0.7 mg E3	Z.P.-19	1.0 mg E2 + 0.07 mg E3
1804-2a replaced on July 3 by	as above	2703-11	9.6 mg E2 + 0.8 mg E3	Z.P.-20	0.5 mg E2 + 0.025 mg E3
0706	as above	Z.P.-13505 Serbios (standard)	0.52 mg E2 + 0.11 mg E3	Z.P.-01607 Serbios (standard)	1.03 mg E2 + 0.075 mg E3
1804-3a IPO-DLO, Netherlands (standard)	as above 0.95mg E2 + 0.05 mg E3

Evaluation of the results

The following parameters were recorded in each orchard: Number of moths (both sexes) captured per week. Pheromone residues measured for all dispenser types at 15-day intervals through out the experimental period. Tree infestation, including counts of infested shoots (counted once per year in early Fall before leaf drop) and numbers of active larval galleries (counted twice per year in the Spring and late Fall after the leaf drop).

Results

Evaluation of dispensers for monitoring and mass trapping

Fig .1 shows the relative biological activity, expressed in total numbers of moths caught per trap in all experimental fields by all traps of each dispenser type tested during 1995, 1996 and 1997. Impressive was the activity of the commercial dispenser Z.P.-01607 (Serbios) in 1997 which appears to be the result of a twofold increase of its pheromone content over that of 1996. The activity of the remaining dispenser types varied from 2.5 to 8.1 during 1995 and 1996.

Fig. 2 shows total numbers of insects caught by all traps of all dispenser types in all experimental fields at different periods of time during 1995, 1996 and 1997.

Fig. 3. shows total numbers of moths caught in the control by one light trap (1995), or two pheromone traps with commercial dispensers (1997) at different time periods. With small deviations from year to year insect catches begin around mid May reach maximum around mid to late June and stop in October. Catches, however, after July are small. These results suggest that the active period of this pest, under the conditions of the experimental region, during which insecticide applications will have their maximum effect, is about two months, i.e. June and July.

Mass trapping

The presence of pheromone traps at the density of 10 traps/ha (1995) and 9 traps/ha (1996 and 1997) in the experimental orchards and the total number on insects removed by them, which are shown in fig. 2, did not reduce pest population densities expressed in total numbers if insects caught by the traps. On the contrary the highest density was observed in the third year (1997). This, however, does not mean that mass trapping is not effective, considering the differences in pheromone trap activity during all these years. Figs 4 and 5 show percent of treeswith infested shoots by this pest and in the trapping orchards and the control and numbers of infested shoots per tree respectively, during 1995,1996 and 1997.

Figure 1. Total number of Zeuzera pyrina moths captured per trap of each dispenser type tested in all experimental orchards during 1995, 1996 and 1997. Within each sex and totals bars with the same letter are not significantly different, Duncan´s multiple range test, P=0.05.

Figure 2. Total numbers of Zeuzera pyrina moths captured by all traps of all dispenser types in all experimental plots except controls at different periods of time during 1995, 1996 and 1997. *Moths are divided in four periods as follows: 1=1-7, 2=8-15, 3=16-22, 4=23-31.

Figure 3. Total numbers of Zeuzera pyrina moths captured in the contro orchard by one light trap (1995) and two pheromone traps (1997, 1998). *Moths are divided in four periods as follows: 1=1-7, 2=8-15, 3=16-22, 4=23-31.

Figure 4. Percent of trees with shoots infested by Zeuzera pyrina in mass trapping plots and the control during 1995, 1996 and 1997. * S = Spring, F = Fall.

Figure 5. Numbers of shoots per tree infested by Zeuzera pyrina in mass trapping plots and the control.

Figs 6 and 7 show percent of trees with active larval galleries and active galleries per tree, respectively. A trend of gradual reduction of tree infestation, expressed in shoot infestation or active galleries was observed. This, however, can not be attributed to the effect of trapping since the same trend was also observed in the control orchard, unless the number of insects removed by the monitoring traps from the control (see fig. 3), had some effect on tree infestation. Most likely, however, this gradual reduction of tree infestation is the manifestation of a 9-year cycle which includes 3 years of population increase, 3 years of population at high levels, and 3 years of population decline (Myers, 1998). For a definite conclusion on the efficacy of the mass trapping method for the control of this pest the experiments must be repeated with the trap found to have the highest activity (Serbios Z.P.-01607).

Figure 6. Percent of trees with active larval galleries of Zeuzera pyrina in the mass trapping plots and the control. * S = Spring, F = Fall.

Figure 7. Numbers of active larval galleries per tree of Zeuzera pyrina in the mass trapping plots and the control.

Mating disruption

Figs 8 and 9 show percent of trees with infested shoots and number of infested shoots per tree, respectively, in the mating disruption orchards and the control. Figs 10 and 11 show percent of trees with active larval galleries and number of active galleries per tree, respectively. In 1997 even though a reduction of tree infestation, in shoot infestation and active gallery counts, was observed both for in the mating disruption and control orchards, the level of reduction during the disruption period (Spring 97 - Fall 97) was much greater in the test than the control orchards. More specifically, percent of trees with infested shoots was reduced by 67.4% (from 91.0-29.7) in the treatments compared to a 36.8% (from 73.1-46.2) reduction in the control. The number of infested shoots per tree was reduced by 92.9 % (from 9.8 to 0.7) in the treatments compared to a 78.6% (from 4.2-0.9) in the controls. Percent of trees with active galleries was reduced by 53.5% (from 77.2-35.9) in the treatments compared to a 27.7% (from 50.5-36.5) in the control. Numbers of active galleries per tree was reduced by 78.9% (from 3.8-0.8) in the treatments compared to a 58.3%(from 1.2-0.5) reduction in the control.

Figure 8. Percent of trees with shoots infested by Zeuzera pyrina in the mating disruption plots and the control.

Figure 9. Numbers of shoots per tree infested by Zeuzera pyrina in the mating disruption plots and the control.

Figure 10. Percent of trees with active larval galleries of Zeuzera pyrina in the mating disruption plots and the control prior (1997 Spring) and after (1997 Fall) disruption.

Figure 11. Numbers of active larval galleries per tree of Zeuzera pyrina prior (1997 Spring) and after (1997 Fall) disruption

Conclusions

The commercial dispenser Z.P.-0107 (Serbios, Italy) was found to have a higher biological activity than any of the other dispenser types tested, both prototype and commercial. The mass trapping method with the use of prototype dispensers for the control of this pest was not effective First year results indicated that the mating disruption method is effective. Preliminary results of the second year are similar or better. Final results will be available at the end of October, 1998.

Acknowledgments

This study has been carried out with financial support from the Commission of the European Communities, Agriculture, Project AIR3-CT-94-1607, "Versatile controlled release dispenser for mating disruption with pheromones". It does not necessarily reflect the views and in no way anticipates the Commissionâs future policy in this area.

References

Abdel-Kawy, A.G.M., El-Bishry, M.H. & El-Kifi, T.A.H. 1992: Controlling the leopard moth borer, Zeuzera pyrina by three entomopathogenic nematode species in the field. Faculty of Agriculture Bulletin, Univ. of Cairo, 43(2): 769-780.

Myers, J.H. 1988: Can a general hypothesis explain population cycles of forest Lepidoptera? Adv. Ecol. Res. 18: 179-242.

Nashnosh, I.M., Baraka, M.M., Ismai, W. & Maayuf, M. 1993: Laboratory evaluation of natural and commercial preparations of entomopathogenic fungi and bacteria on the leopard moth, Zeuzera pyrina L. (Lepidoptera:Cossidae). Arab. J. Plant Protection 11(2): 73-76.

Pasqualini, E. 1989: Technique di lotta biologica in sistemi di lotta integrata sulle pomacee. Inf. Agrar. Verona 45(48): 67-78.

Pasqualini, E. Antropoli, A. Faccioli, G. 1992: Attractant performance of a synthetic sex pheromone for Zeuzera pyrina L. (Lepidoptera, Cossidae). Bollettine dellâ Istituto di Entomologia Guito Grandi della Universita degli Studi di Bologna 46: 101-108.

Pasqualini, E. Antropoli, A. Faccioli, G. & Molfese, M. 1993: Zeuzera pyrina L. (Lepidoptera, Cossidae): Results of five year researches on sex attractant. Bull. OILB/SROP 16(10): 189-194.

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