Ecological Factors Affecting Artificial Culture Of Mirid Bug Cyrtorhinus Lividipennis (Reuter)

Mirid bug, Cyrtorhinus lividipennis (Reuter), is the important predator of rice leaf-and planthoppers. It migrates together with rice planthoppers from rice growing regions of Southeast Asia and southern China to the main rice production areas in Yangtze Delta, and to Japan and Korea every year. The abundance of C.lividipennis population in early rice growth season is too low to efficiently control the population of rice planthoppers, since the population establishment of C. lividipennis in paddy fields could match up the rapid population growth of the main rice planthoppers, brown planthopper and white backed planthopper. To maximize the impact of C. lividipennis in natural control of rice planthoppers, the massive culturing and artificial releasing techniques are needed. Unfortunately, these techniques are not available in China. In this paper, key ecological factors affecting massive culture of C. lividipennis were preliminarily explored on the effects of temperature, starvation, host plants, substitute foods and artificial diet on C. lividipennis for assisting the further study of artificial massive culture and release in paddy fields. The results are as follows:1. The successive effects of different temperatures on the growth, development and reproduction of Cyrtorhinus lividipennis Reuter were determined for three successive generations under19℃,23℃,27℃and31℃in laboratory. The results showed that the female nymph duration markedly shortened with the increase of successive generations under19℃, while obviously successive effect was not recorded at23℃,27℃and31℃. There were no successive effects found on male nymphal duration and nymphal survival rate under all tested temperatures. There were no significant differences on weights of female adults among various temperature treatments. The number of offspring decreased significantly in the3rd generation compared to that in the1st and2nd generation both at19℃and31℃, especially at31℃. The longevities of female adults reduced significantly with the increase of successive generations under19℃, while no obvious changes were observed in the longevities of the male adults with the same temperature treatment. It was implied that significant cumulative effects were occured on adult fecundity and female nymphal duration at19℃, and on female adult fecundity and longevity at31℃.2. At26℃, the mean survival duration had no significant differences between lower instar nymphs and higher instar nymphs when fed on rice plant with water, while the same survival duration of3rd instar nymphs and4-5th instar nymphs were observed fed with nothing. However, the mean survival duration of4-5th instar nymphs was obviously longer than that of the3rd instar nymphs when fed on water only, it implies that the rice plant could provide nutrition for the lower instar nymphs. While at15℃, rice plant negatively effected the adult survival, and the longevities of adults fed on rice plant were shorter than those on water only.3. Both male and female adults of C. lividipennis did not show significant preference to odor source of tested host plants, however, the male adults showed a little repellent to Eleusine indica (L.) Gaertn. Rice plant is the favorite oviposition host plant followed by Echinochloa crusgalli (L.) Beauv among five candidate host plants used in this experiment. The oviposition rate on E. crusgalli is18.23%, while76.05%on rice. Female adults prefer to lay eggs in leaf veins, except mostly laying eggs in leaf sheathes of the middle part of Digitaria sanguinalis (L.) Scop.4. Mirid bug adults showed no preference to Corcyra cephalonica eggs exposed to30W UV for different durations (15min,30min,45min) and kept at4℃for different durations(2d,4d,6d). Second instar nymphs did not prefer to the eggs treated with30W UV and4℃stored, as well as to those stored at26℃for different durations (Id,2d,3d). However,4th instar nymphs showed significant preference to the eggs stored at26℃for3days.5. Preliminary developed artificial diets satisfied the demands of C. lividipennis to successfully finish its life cycle with55.4%nymphal survival rate. Compared with the C. lividipennis fed on brown planthopper eggs and C. cephalonica eggs, those fed on tested artificial diets showed longer nymphal duration, lighter female weight, weaker predation ability and less fecundity.