| The green lacewing Chrysopa pallens (Rambur) and Chrysopa formosa Brauer are excellent natural enemies, which have good application prospect and can be used in the control of many kinds of soft-bodies pests, such as aphids, spider mites, whiteflies and so on. They have a wide distribution, high fecundity and are carnivorous in both larval and adult stage. In recent years, many researches are on its biological characteristics, predation ability, diapause and artificial diet, but there is still no study on its application in greenhouse and farmland up to now. So far the establishment of adults of green lacewing are not ideal in field. Successful commercial products of lacewings in abroad is eggs, larvae, not adults. Based on this, we perform the research on dispersal distance and activity patterns of C. pallens and C. formosa under greenhouse conditions. We primarily determine the effect of plant, temperature, release height, prey on its behavior. Besides, it is meaningful to assess its potential application in biological control. The main results are as follows:We used fluorescent to be the markers for green lacewings so as to easily track them in night. Fluorescent is a suitable sort of marking material, which has many advantages, such as low cost, non-toxic, simple operation., time-saving and easy to obtain. Meanwhile, it has no significant impact on the flight capability of green lacewings. After been marked with fluorescent, lacewings are easily found at night.Biological characteristics of plant have a significant effect on the diffusion behavior of lacewings. Plant height, plant odors, leaf size and other factors will effect the behavior of lacewings. On the same kind of plant, the behavior of C. pallens and C. formosa have no significant difference. Whereas, the behavior of the same kind of lacewings on different kinds of host plant show some difference. C. pallens and C. formosa substantially prefer cucumber than tomato. When we release lacewings on cole, Chinese cabbage, spinach and radish, there is not any lacewings on vegetables. All of them are on the ceiling and walls of the greenhouse. After adding8tall tabacco among those vegetables, approximately20%lacewings will choose tabacco as the habitat other than the ceiling and walls. Meanwhile, there is no significant differences between C. pallens and C. formosa. When we add coriander among cucumber, the number of lacewings on cucumber is more than control group. At the same time, the number of lacewings on ceiling and walls decrease dramatically.Temperature has remarkable impact on lacewings dispersal behavior. While we release lacewings at15℃,20℃,25℃,30℃four temperature conditions, the average dispersal distance of lacewings will gradually become longer as the temperature increasing. The mainly activity area of lacewings on plant also transfer from the lower portion to the upper part. At15℃,there are prominent differences between C. pallens and C. formosa (p=0.0336<0.05). It sates that the diffusion capability of C. formosa is better than C. pallens at low temperature.Prey do not significantly affect the the dispersal behavior of lacewings. From7:00to23:00, we found that the number of C. pallens and C. formosa on the plant have no significant increased after soybean aphid or Bemisia tabaci had been put on the plant.Release height effect the diffusion of lacewings significantly. We release C. pallens and C.formosa at60cm,120cm,180cm distance from the ground. With the release height increased, the main distribution area of lacewings transfer from the lower part of plant towards the upper part and the ceiling of greenhouse. There are no conspicuous differences between the two kinds of green lacewing diffusion distance and spatial distribution. When lacewings released at180cm, the number of lacewings on lower part of plant is5%of total released. Simultaneously, the number of lacewings on ceiling of green house and upper of plant is over90%of total released. |
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