Effects Of Host Plants On The Population Parameters,Activities Of Detoxification Enzymes And Insecticide Susceptibility In Laodelphax Striatellus

The small brown planthopper?SBPH?,Laodelphax striatellus?Fallén?,has a wide host range,besides feeding on rice,it can also harm gramineous plants such as wheat,corn and weeds,and can transfer hazards between different hosts to adapt to seasonal and environmental changes.To evaluate different host plant effects on SBPH,the life table parameters of SBPH reared on two cultivars of rice?Zixiangnuo 2315 and Wuyujing 3?and wheat?Jimai 22 and Nongda 26?and one grass weed?Echinochloa crusgalli?using the age-stage,two-sex life table,along with corresponding activities of three detoxifying enzymes?carboxylesterase?CarE?,glutathione-S-transferase?GST?,and mixed-function oxidase?MFO??in short time.After feeding SBPH on these five hosts for 6 generations,the sensitivity of SBPH to 4 insecticides including trifluoropyrimidine,imidacloprid,thiamethoxam and chlorfenapyr and the changes of the activities of 3 detoxification enzymes were determined.Main research results were as follows:Host plant species had effects on population parameters of SBPH.Different varieties of the same host plant also have significant effects on the population parameters of SBPH except 4th instar nymphs.Among the individuals of SBPH reared on five host plants,rice‘Zixiangnuo 2315'and wheat‘Nongda 26'had the highest intrinsic rate of increase,finite rate of increase and net reproductive rate and the shortest mean generation time.Female age-specific fecundity(f_xj),population age-specific fecundity?m_x?and l_xm_x of rice‘Zixiangnuo 2315'and wheat‘Nongda 26'SBPH populations are the highest.Age-stage survival rate(s_xj)showed that the survival rate of nymph,female adult and male adult of SBPH fed on rice and wheat was significantly higher than that of E.crusgalli.Age-stage specific life expectancy(e_xj)of SBPH fed on rice and wheat was higher than that of E.crusgalli.Age-stage specific reproductive value(v_xj)of female adults of SBPH was feeding on rice‘Zixiangnuo 2315',E.crusgalli,wheat‘Nongda 26',wheat‘Jimai 22'and rice‘Wuyujing 3'in descending order.There was no significant difference in population age-specific survival rate?l_x?between SBPH feeding on different host plants.In summary,rice‘Zixiangnuo 2315'and wheat‘Nongda 26'may be more suitable hosts than the other three hosts.Within 72 hours after feeding the adults of SBPH with five host plants,the changes of CarE and MFO activity in the body showed a trend of first rising,then falling,then rising,and GST activity showed a trend of first rising and then falling.After individuals had been reared for 72 h,levels of CarE activity were greatest in those reared on E.crusgalli and lowest in individuals reared on rice‘Wuyujing 3'.Levels of GST activity were greatest in adult SBPH reared on‘Nongda 26'and lowest in individuals reared on‘Zixiangnuo 2315'.Levels of MFO activity were greatest in individuals reared on‘Zixiangnuo 2315'and lowest in individuals reared on E.crusgalli.The results showed that the activity of three detoxification enzymes increased after the SBPH transferred to five host plants,which may be related to the metabolism of plant secondary metabolites and allelochemicals after reared on five host plants.After feeding SBPH for 6 generations in succession with 5 host plants,the susceptibility of 3rd instar nymphs of SBPH to triflumezopyrim has not changed basically and there is no difference between host plants.The sensitivity of 3rd instar nymph of SBPH feeding on wheat to imidacloprid,thiamethoxam and cyantraniliprole increased obviously,and there was no difference between the two wheat varieties.The sensitivity of 3rd instar nymphs of SBPH feeding on rice to imidacloprid and cyantraniliprole has not changed basically.The sensitivity of 3rd instar nymphs of SBPH feeding on E.crusgalli to imidacloprid and cyantraniliprole showed a certain increasing trend,but the sensitivity to thiamethoxam has not changed basically.The results of detoxifying enzymes activity also showed that the CarE and MFO activities in the 3rd instar nymphs of SBPH were significantly decreased when fed with different host plants for 6 generations,but the GST activity did not change much.The activities of three detoxifying enzymes of the 3rd instar nymphs of the same generation of SBPH fed on different host plants are different,and the activities of three detoxifying enzymes of the 3rd instar nymphs of SBPH fed on two wheat varieties are lower.The results showed that the host plant induced the decrease of detoxifying enzymes activity of SBPH was the main reason for the increase of sensitivity of SBPH to insecticides.