IOBC wprs Bulletin Vol 22(9), 1999

Field trapping of lacewings with aphid pheromones

K. S. Boo, S. S. Kang, J. H. Park, J. A. Pickett, L. J. Wadhams

The lacewings (Neuroptera: Chrysopidae) are an important group of predators against small insect pests such as aphids. In South Korea Chrysopa cognata is the most common species which is now under study for a possibility of utilization as a biological control agent against aphids in protected horticulture. This species has another advantage due to its insectivorous habit even during adult stage, in contrast to other Chrysoperla species. One group of entomologists in South Korea are trying to develop an artificial diet for this species so that this species can be released in mass in green houses or protected horticultural structures. But one problem is how to keep them in such structures as long as possible. One possibility is using some attractive chemicals so that they may stay there longer.

In our previous communication (Boo et al. 1998) C. cognata was shown to be influenced by aphid sex pheromone components, (4aS,7S,7aR)-nepetalactone and (1R,4aS,7S,7aR)-nepetalactol, in EAG measurements and in an olfactometer bioassay. However, field trapping trials with water traps at a peach orchard were not so successful. It turned out, from this report, to be due to very low level of its population at the orchard caused by heavy spray of insecticides.

This report is concerned with results from field trapping trials with sticky traps at a chestnut orchard, an arboretum and our college campus. At these places insecticides were not or rarely sprayed and consequently we could capture many number of them with those chemicals during last three years. C. cognata was significantly more attracted to nepetalactol than nepetalactone, which was again significantly more effective than a solvent, hexane. For example, the number of C. cognata trapped with nepetalactol was 3,065 against 231 with nepetalactol at field trappings during Aug. 5 to Sept. 3, 1998. The combination of the two chemicals at various ratios did not improve the catching efficiency. The number of lacewings caught increased with the amount of chemicals, up to 30 mg per a lure, the highest amount tested in this series of experiments. The lacewing was caught in traps mainly during nights, especially from 7.30PM to 1.00AM in July and August in South Korea (at about 38° latitude). In November when outdoor temperature is quite low, however, a few of them were caught during the daytime. Trap color, as expected, did not influence the trap efficiency. The catch extended throughout the season, from May to November, with more numbers in July and August. For a dispenser for aphid sex pheromone chemicals, rubber septa were much more effective than glass vials, in terms of longevity and attractivity. Besides C. cognata, a few individuals, 11 of Chrysopa formosa and 6 of Chrysopa phyllochroma, were also trapped together during Aug. 5, to Sept. 3, 1998. But these numbers are much fewer if compared to 3,296 C. cognata caught during the same period. This seemed to be due to the low level of C. formosa population, not due to lower attractiveness to this species. Even Chrysoperla carnea was shown to be responding to these chemicals in EAG measurements (T. Baker, personal communication). Another interesting aspect was that those lacewings caught were mostly males, regardless of the species. It was hard to catch female lacewings with the traps, even though they were found to be active to these chemicals in EAG measuremtents. The aphid alarm pheromone, (E)-ß-farnesene did not attract any lacewings in field trappings, just like in its inactivity in EAG measurements(Boo et al. 1998).

Key words: lacewings, sex pheromone, Chrysopa cognata, Chrysopa phyllochroma, Chrysopa formosa

Reference

Boo, K.S., Chung, I.B, Han, K.S, Pickett, J.A. & Wadhams, L.J. 1998: Response of the lacewing Chrysopa cognata to pheromones of its aphid prey. J. Chem. Ecol. 24: 631-643.

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