| Rice stem borer and planthopper are the main pests in rice production and an important factor affecting rice yield and quality.In recent years,some species of rice stem borer and planthopper have aggravated in some areas of China.At present,chemical control is still the main means of rice stem borer and planthopper control,but due to the increasingly problem of resistance,lead to the decline in the effectiveness of common insecticides,and it is urgent to develop new and effective insecticides.Therefore,we firstly analyzed the field and lamp lure data of rice stem borer and planthopper in Jiangsu Province for recent three years,and investigate the field wintering rice stem borer and planthopper in Lishui in 2017 and 2018,in order to clarify their occurrence status;Secondly,the resistance of C.suppressalis and L.striatellus were monitored to provide guidance for field insecticides use;Finally,we screened high-synergistic effect mixtures for C.suppressalis and L.striatellus to prolong the service life of "frequently-used insecticides".1.Occurrence status of ricestem borer and planthopper in Jiangsu ProvinceWe analyzed field survey data and lamp lure data of rice stem borer and planthopper form Wujiang,Suining,and Yangzhong,during 2016 and 2018,and investigated the field wintering rice stem borer and planthopper from Lishui in 2017 and 2018.The results showed that during 2016 and 2018,(1)three species of rice planthopper(L.striatellus,S.furcifera and N.lugens)generally occurred slightly,the peak number of insects per hundred holes were between 0-397.99(slightly to moderately slight occurrence)in Jiangsu.(2)The C.suppressalis generally occurs slightly,and massively occurs in some area,but was not detected in Yangzhong and Wujiang.The peak number of C.suppressalis per mu in Suining were between 86.8-145(slight occurrence).In 2017,the residual number of C.suppressalis after winter per mu in Lishui reached to 1040.52(massive occurrence).(3)The S.inferens occurs in a moderate level,but massively occurs in some area.The peak number of insects per mu in Wujiang and Suining were between 18-505(slight to massive occurrence),but was not detected in Yangzhong.(4)The C.medinalis slightly occurred,and the peak number of eggs and insects per mu in five(3)generation were between 3600-18000(slight to moderately slight).(5)The S.incertulas was not detected in the surrounding lamp lure and field.In summary,we should be focued on the control of L.striatellus,S.furcifera,C.medinalis,S.inferens,and C.suppressalis(in Lishui and Suining),and partly on N.lugens2.Resistance monitoring of C.suppressalis and L.striatellus in Jiangsu Province and its surrounding areasThe resistante level of C.suppressalis and L.striatellus in Jiangsu Province and surrounding areas to insecticides were determined in this study,which could provide guidance for field insecticides use.(1)In 2017-2018,we used the topical application to determine the resistance of Chilo suppressalis from different areas to a variety of commonly-used insecticides(chlorantraniliprole,monosultap,avermectin and fluralaner).The results showed that C.suppressalis were sensitive to monosultap at low level with resistance ratio(RR)at 2.37-6.73,reducing sensitivity to avermectin(RR between 3.11-3.50),sensitive to fluralaner(RR between 0.65-1.10).The C.suppressalis of Changfeng had low to moderate level resistance to chlorantraniliprole(RR between 5.83-16.08)is the highest resistance.In view of the above results,the frequency of useage of chlorantraniliprole in the field could be reduced in Jiangsu to avoid the continuous increasing resistance.(2)In 2018,the resistance of L.striatellus to five insecticides(dinotefuramide,ethiprole,thiamethoxam,fluralaner,and imidacloprid)were determined by the topical application from Wujiang.The results showed that the L.striatellus were sensitive to the tested insecticides,and the RR for dinotefuran,ethiprole,thiamethoxam,fluralaner and imidacloprid were 1.57,0.76,0.99,1.52 and 2.01,respectively,which indicates that the tested insecticides can still be used for the control of L.striatellus.3.Screening of high-efficiency mixed insecticides for C.suppressalis and L.striatellusIn this paper,a variety of mixed insecticides against C.suppressalis and L.striatellus were determined by the topical application and diet incorporation method,in order to screen out the mixtures with high synergistic effect.(1)We used topical application determined the combined effect of 3 mixtures(fluralaner with chlorpyrifos,imidacloprid and emamectin benzoate,respectively)on L.striatellus female adult,the mixture of fluralaner with chlorpyrifos(3:2)and with imidacloprid(1:4),showed synergistic effect(CTC as 142.68 and 141.52,respectively).(2)We used diet incorporation method determined the combined effect of 6 mixtures(broflanilide with phoxim,ethiprole,indoxacarb,chlorantraniliprole,emamectin benzoate,phenthoate,respectively)on C.suppressalis 4th instar larva,the mixtures of broflanilide with indoxacarb(1:1 and 20:1)and with ethiprole(20:1),showed synergistic effect(CTC as 152.60,191.15 and 163.34,respectively).(3)We used topical application determined the combined effect of 4 mixtures(ethiprole with chlorantraniliprole,monosultap,chlorpyrifos and avermectin,respectively)on C.suppressalis 4th instar larva,the mixture of ethiprole with avermectin(3:2),showed synergistic effect(CTC as 157.54).Therefore,when controlling the L.striatellus in the field,the mixture of broflanilide and avermectin(ratio 1:20 and 20:1),and fluralaner with chlorpyrifos(3:2)and with imidacloprid(1:4)could be considered.The mixtures of ethiprole and avermectin(2:3 and 3:2),broflanilide with indoxacarb(1:1 and 20:1)or with ethiprole(20:1),and ethiprole with avermectin(3:2),showed synergistic effect on C.suppressalis 4th instar larva with CTC>150. |
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