The Predation And Control Effects Of Harmonia Axyridis On Myzoxallis Karicola And Their Sensitivity Evaluation To Insecticides And Fungicides

Castanea mollissima was one of the earliest cultivated economic tree species in China.As pest of chestnut,Myzoxallis karicola had been caused serious harm to chestnuts.This study focused on this insects and measuring and comparing the its predatory response and field controled effectiveness against M.karicola and several other preies,the predatory natural enemy of the beetle,Harmonia axyridis,and evaluated the safety of several commonly used insecticides and fungicides in chestnut orchards against the 4th instar larvae and adults of H.axyridis.The mainly research results and conclusions were as follows:1.The predatory response of the H.axyridis to M.karicola and other preyThe predatory functional responses of H.axyridis to M.karicola,Aulacophoroides hoffmanni,Chaitophorus salinigri,and Drosophila melanogaster all conforms to the Holling II model.When the prey density was the similar,the control ability(a/Th)of H.axyridis to M.karicola and several other prey was as follows: M.karicola(392.9)> A.hoffmanni(338.6)> C.salinigri(276.28)> D.melanogaster(171.34);The maximum daily predation(1/Th)of M.karicola and several other prey was as follows: M.karicola(434.78)> A.hoffmanni(384.62)> C.salinigri(333.33)> D.melanogaster(250).The H.axyridis on the larvae of M.karicola,A.hoffmanni,C.salinigri,and D.Larvae of prey.The predation amount of H.axyridis on M.karicola was significantly higher than the other two aphids and feed insects(P<0.05).2.Field Control Effect of H.axyridis on M.karicolaThere was no significant difference(P<0.05)at the rate of M.karicola population decline between treatments in H.axyridis ratio of 1:100 and 1:50,but it was significantly higher than that of treatments with H.axyridis ratio of 1:150(P<0.05);The treatment conducted in the experiment show extremely significant differences compared to the blank control(P<0.01).In summary,when the ratio of H.axyridis to M.karicola was 1:100 and 1:50,the control effect of adult H.axyridis beetles on M.karicola was better than that H.axyridis to M.karicola ratio of 1:150.3.Sensitivity evaluation of H.axyridis to several pesticidesThe used of beta cypermethrin insecticide in chestnut orchards,was associated a high risk to the 4th instar larvae and adults of H.axyridis beetle;Similarly,avermectin had been found to take lower safety against 4th instar larvae and adults of H.axyridis beetles,indicating a high risk;imidacloprid also had posed a high risk to adult H.axyridis beetles;chlorbenzuron and chlorantraniiprole had been found to had a moderate risk to the 4th instar larvae and adults of H.axyridis.The 4th instar larvae and adults of H.axyridis were susceptible to five fungicides frequently utilized in Chinese chestnut orchards,including difenoconazole,carbendazim,thiophanate-methyl,mancozeb and prochloraz.The safety of difenoconazole against4 th instar larvae of H.axyridis was poor,with high risk,and the other four fungicides against the 4th instar larvae and adults of H.axyridis were medium risk.