The Effects Of Triflumezopyrim On The Feeding Behaviour And Reproduction Of Rice Planthoppers

The rice planthoppers,Nilaparvata lugens Stal(Homoptera:Delphacidae)and Sogatella furcifera Horvath(Homoptera:Delphacidae),are major pests which threaten the rice production seriously in rice producing areas of Southeast Asia.Triflumezopyrim,the novel mesoionic insecticide from DowDuPont,was found to be effective in suppressing the plant hopper population.However,the insecticidal mechanism and sublethal effect of triflumezopyrim on rice planthopper remain unclear.To evaluate and use triflumezopyrim reasonably,we selected three concentrations(LC10,LC50 and LC90)of triflumezopyrim to examine the effects on feeding behaviour and reproduction of rice planthoppers which exposed to the insecticide via contact and systemic routes.Pymetrozine was used as control insecticide.The results were as follows:(1)The effects of three concentrations triflumezopyrim on the feeding behavior of N.lugens and S.furcifera were recorded using electrical penetration graph technique(EPG).The EPG signals for the feeding behaviors of two kinds of planthoppers were classified into six different waveforms,NP,N1,N2,N3,N4 and N5,which corresponded to non-penetration,stylet penetration into epidermis,salivation andmovement of stylet,extracellular movement of stylet near the phloem region,sap ingestion in phloem,and water ingestion in xylem,respectively.LC10 triflumezopyrim treatment had no significant effect on the duration of NP waveforms of both planthoppers treated with either route.In the triflumezopyrim treatments at LC50 and LC90 concentrations,the duration of NP waveforms of N.lugens and S.furcifera that treated via systemic route was significantly prolonged by 105.3%?270.4%compared with control((46.0±3.0)min).Contact treatment with LC50 and LC90 triflumezopyrim also prolonged the duration of NP waveforms The probing frequency(N1)of planthoppers in systemic treatments with different concentrations triflumezopyrim did not differ from that in control group.The probing frequency of N.lugens which exposed to triflumezopyrim(LC10 and LC50)via contact route was increased;while,that of S.furcifera exposed to triflumezopyrim(LC10,LC50 and LC90)was decreased.The duration of N2 waveforms of both planthoppers were prolonged in either treatment with different concentrations triflumezopyrim.The duration of N3 waveforms of both planthoppers exposed to LC90 triflumezopyrim via systemic route or to LC50 and LC90 triflumezopyrim via contact route,were distinctly shortened.The duration of N4 waveforms of both planthoppers that exposed to LC50 and LC90 triflumezopyrim via systemic route was shortened by 37.2%?77.7%,and that treated via systemic route was shortened by 39.7%?70.4%.No obvious effect of triflumezopyrim on the total duration of N5 waves of N.lugens or S.furcifera was observed.LC50 and LC90 pymetrozine treatments caused similar shortened N4 waveform duration and prolonged NP waveform duration in N.lugens or S.furcifera.In conclusion,triflumezopyrim(LC50 and LC90)showed obvious anti-feeding effect on planthoppers,which facilitated the non-penetration and salivation but inhibited the extracellular movement of stylet near phloem region and phloem nutrient-ingestion.(2)The effects of triflumezopyrim on the reproduction of three pair combinations(?t×(?)ck,?ck×(?)t and ?t×(?)t)in N.lugens were examined using as untreated combination(?ck×(?)ck)as control.The results indicated that sublethal concentrations(LC10)of triflumezopyrim didn't affect the reproduction of N.lugens.LC50 and LC90 triflumezopyrim treatments via systemic route also had no influence on the preoviposition in the three mating combinations.However,the preoviposition of N.lugens directly exposed to LC50 triflumezopyrim was obviously prolonged in ?ck×(?)t and ?t×(?)t mating combinations.LC50 and LC90 triflumezopyrim treatments via systemic route decreases the number of eggs by 27.9%?41.1%in the three pair combinations(?t×(?)ck,?ck×(?)t and ?t×(?)t).Contact treatment with LC50 and LC90 triflumezopyrim caused similar reduction of fecundity.However,no obvious difference in egg hatchability was obtained in triflumezopyrim treatments and the control.LC50 and LC90 triflumezopyrim treatment via contact and systemic routes reduced the titer of JH ? by 25.8%-37.2%in N.lugens female.LC50 and LC90 triflumezopyrim treatments via systemic route decreased the vitellin content by 25.7%and 41%%in the fat bodies,and by 24.2%and 33.6%in the ovaries.Similar inhibiting effect on vitellin content also occurred in contact treatment.LC50 and LC90 pymetrozine adversely affected the fecundity and vitellin content of females treated with insecticide via systemic route.The development of the internal reproduction organs of N.lugens female was severely inhibited by triflumezopyrim.The ovary development of newly emerged N.lugens was delayed,and the ovariole was invisible.The ovariole of the female adult at 3 days after eclosion was shorter and the yolk protein was not found in the vitellarium.5 or 7 days after eclosion,the number of mature eggs in the ovary was significantly lower than that in the control group.The result showed that LC50 and LC90 triflumezopyrim could decrease the fertility of N.lugens.Triflumezopyrim had inhibitory effects on the reproductive hormone,nutrients and the ovary development in N.lugens.