Interaction effect between Lyonetia clerkella and Grapholitha molesta sex pheromones

Abstract:【Objective】Lyonetia clerkella L.(Lepidoptera, Lyonetiidae) and Grapholitha molesta B. (Lepidoptera, Tortricidae) are important pests in orchards, which damage leaves, twigs and fruits of peach, pear, apple, plum, apricot and other fruit crops. Due to the damaging characteristics of the two pests, the control effect by chemical pesticide is limited. Insect sex pheromones have been widely used in integrated pest management including the sex pheromone of L. clerkella and G. molesta. Their occur- rence periods of two insects overlap throughout the year. The purpose of this study was to explore the interaction effect between two sex pheromones by means of Electroantennogram (EAG) and field trap- ping tests. One of the objectives of this study was to test whether male moths of L. clerkella and G. mo- lesta can perceive sex pheromones of each other; and another objective was to determine whether the two synthetic sex pheromones could be blended into a lure for monitoring and controlling the both in- sect pests simultaneously. The results can provide a basis for the development of a blending lure to save the cost of management and improve multi-species control efficiency.【Methods】This study was divid- ed into two parts: EAG test and field trapping test. The sex pheromone of L. clerkella used was 14-meth-yl-1-octadecene and the sex pheromone of G. molesta was composed of (Z)-8-dodecenyl acetate (Z8-12: OAc), (E)-8-dodecenyl acetate (E8-12:OAc) and (Z)-8-dodecen-1-ol (Z8-12:OH) in a ratio of 95∶5∶5. In the EAG test, the different doses of sex pheromone of G. molesta (0.1, 1.0, 10.0, 100.0 and 500.0 μg) were used to stimulate the antenna of L. clerkella male moth, and then the 5 same pheromone doses ofL. clerkella were to stimulate the antenna of G. molesta male moth conversely. The paraffin oil was used as control. Each EAG test was repeated for 8 times. In the field trapping test, the different doses of sex pheromone of G. molesta (50.0, 100.0, 200.0, 300.0 and 500.0 μg) were mixed respectively with 1.0 mg pheromone of L. clerkella, and then 1.0 mg and 2.0 mg doses of sex pheromone of L. clerkellawere mixed respectively with the 50.0 μg pheromone of G. molesta. In addition, 1.0 mg pheromone ofL. clerkella and 50.0 μg pheromone of G. molesta were used as control respectively. The type of trap used was triangle trap that was hung on the branch at a height of 1.5 m above the ground. Check was done once a week and the location of traps in the same block was exchanged circularly. Five replicates were used for each treatment.【Results】Male moth of L. clerkella could perceive as low as 0.1 μg sex pheromone of G. molesta and the responses of 5 doses (0.1, 1.0, 10.0, 100.0 and 500.0 μg) were signifi- cantly higher than those of control (p < 0.05). The EAG responses of G. molesta increased with the in- crease of sex pheromone of L. clerkella. When the dose was 0.1-10.0 μg, there was no significant differ- ence compared to control (p > 0.05); when the dose increased to 100.0 μg, there was significant differ- ence compared to control and 0.1-1.0μg treatments (p < 0.05), but no significant difference compared to 10.0 μg (p > 0.05); when the dose increased to 500.0 μg, the EAG response was the highest, which was significantly higher than control and 0.1- 100.0 μg treatments (p < 0.05). The field trapping test showed that when 50.0, 100.0, 200.0, 300.0 and 500.0 μg sex pheromones of G. molesta were mixed with 1.0 mg sex pheromone of L. clerkella respectively, the average L. clerkella moth catch per trap per week was slightly lower than control (1.0 mg sex pheromone of L. clerkella), which were 39.8, 42.1, 43.5, 41.0, 38.2 and 46.3 respectively, and there were no significant differences among the six relative trapping rates (p > 0.05), which were 16.50% ± 1.44% , 16.13% ± 1.32% , 17.27% ± 0.82% , 16.80% ± 1.00%, 15.21%±0.41% and 18.09%±0.76% respectively. When 1.0 mg and 2.0 mg sex pheromones ofL. clerkella were mixed with 50.0 μg sex pheromone of G. molesta, the average G. molesta moth catch per trap per week was also slightly lower than control (50.0 μg sex pheromone of G. molesta) but there was also no significant difference among the three relative trapping rates (p > 0.05), which were 17.89%±5.20%, 22.98%±6.07% and 35.17%±3.80% respectively.【Conclusion】Male moth of L. clerkellaand G. molesta can perceive sex pheromones of each other at some dosages and different doses of mixed at- tractants containing both L. clerkella and G. molesta synthetic sex pheromones had no significant effect on the two moth captures in the fields. Therefore, to save the manpower and cost, the two pheromone blend can be used to monitor and control both L. clerkella and G. molesta simultaneously in orchards.