Effect Of Green Control Technology On The Populations Of Rice Planthoppers And Their Natural Enemies And Avaluation Of The Effect Of Pymetrozine On Cyrtorhinus Lividipennis Treated With The Sublethal Concentration Of Insecticide

Rice planthoppers(Hemiptera:Delphacidae)are considered to be the most economically important rice pests in China.Cyrtorhinus lividipennis(Reuter)(Hemiptera:Miridae)preys on eggs and young nymphs of rice planthoppers and plays an important role in pest control.Rice spiders are also important predatory natural enemies of rice planthoppers and important biological control agents.Pesticides are designed to be extremely effective at killing targeted insect pests,but they also have the potential to adversely affect non-target natural enemies not only through lethal effects but also through sublethal effects.The effects of environmentally friendly pest control techniqueson on the field populations of rice planthoppers and their natural enemies were examined to reduce the use of chemical pesticides and to protect environment and natural enemies.Chemical control is still the first choice for many farmers to manage rice pests and diseases.Pymetrozine is a good pesticide in green control technology and previous study indicated that sublethal concentrations of pymetrozine stimulated reproduction of C.lividipennis.However,the predatory capability and fecundity of progeny surviving from pymetrozine exposed individuals remains unclear.In this paper,the effect of pymetrozine on the progeny form surviving individuals treated with the insecticide was also evaluated.The results are as follows.(1)The effects of environmentally friendly pest control techniques(non-chemical-control:the LED light trap,sex pheromone lure and biopesticide)on the field populations of rice planthoppers and their natural enemies(predatory spiders and C.lividipennis)were surveyed in rice paddy in Yixing.Rice paddy using chemical insecticides pymetrozine and nitenpyram was considered as the control.The data on 7th,Sep indicated the number of N.lugens in aon-chemical control rice paddy(18.67±1.33 individuals per 100 hills)was higher than that of the control(13.33±1.33 individuals per 100 hills)increasing by 40.01%,and it also showed that the number of Sogatella furcifera was significantly lower than those of control.No significant difference in spiders population was observed between the non-chemical control paddy fields and the control.The data on 14th,Sep and 22th,Sep indicated that the number of C.lividipennis was lower in non-chemical control rice paddy than the control.The result indicated that the environmentally friendly pest control techniques could control the density of rice planthopper when the planthopper was not serious.Previous laboratory studies have shown that sublethal concentrations of pymetrozine can stimulate the reproduction of C.lividipennis.The increased number of C.lividipennis in the control paddy might be resulted from the stimulatory effect of pymetrozine on this predator.This hypothesis needs to be confirmed by more experiments.(2)Under laboratory conditions,the effects of sublethal concentration of pymetrozine(LC20)on the orientation behavior,predatory capability,fertility,and longevity of adults in F1 generation(progeny surviving from pymetrozine exposed individuals)were examined.The results indicated that individuals in F1 generation could distinguish between volatiles from Nilaparvata lugens infested rice plants and those from healthy rice plants.With the increase of nymph density of N.lugens,the predation of individuals in F1 generation increased.When the densities of N.lugens were 50/vial,the mean consumption of C.lividipennis in pymetrozine treatment ♀pymetrozine×♂pymetrozine increased by 20.4%and 28.9%,respectively,compared to those treatment combinations ♀pymetrozine×♂control and ♀control×♂control.Sublethal concentration of pymetrozine had no influences on the relative expression level of Vg,longevity of adults,pre-oviposition period,fecundity and egg hatchability,which itindicated that pymetrozine could be compatible with C.lividipennis and enhanced the control efficiency of pest control.