| Maize is an important food crop in China.At present,the planting area and total yield rank first in China.The lepidopteran Asian corn borer(ACB),Ostrinia furnacalis(Guenée)is one of the most destructive pests of Zea mays.Due to the lack of natural resistant corn varieties,physical control,chemical control,and biological control are usually used to control ACB.Trichogramma dendrolimi Matsumura(Hymenoptera:Trichogrammatidae)and Beauveria bassiana(Bals.)are the main biological control methods used to protect corn production.They have made important contributions to corn production protection,farmers’income increase and farmland ecological protection in Northeast China.However,these two methods have some limitations when used alone.Trichogramma only parasitic corn borer eggs,but has no control effect on larvae,whereas B.bassiana mainly infect corn borer larvae,has no parasitic effect on corn borer eggs.The purpose of this study is to achieve sustainable pest management of the two stages of ACB.In this study,first of all,suitable adjuvant was screened for fungal conidia adhering and observed the effects of B.bassiana on the emergence,survival time and parasitization rate of T.dendrolimi.Secondly,the transmission and infection process of B.bassiana vectored by T.dendrolimi(TCB)was observed by GFP.Thirdly,screen house and field trial were carried out for egg parasitism and larvae infection of pest.At first,in this study,adjuvants were used as auxiliary agents for adhesion of B.bassiana on A.pernyi eggs.The emergence rate and amount of T.dendrolimi showed no significantly difference compared to that of control indicated that different additives and B.bassiana spores had no effect on Trichogramma.0.1%(w/v)starch solution was selected from several adjuvants due to its highest ability to carry fungal conidia,over 3.6×10~4 conidia per wasp.The corrected parasitism rate of TCB and non-TCB were 50.19%and 51.70%,respectively,with no significant difference.The average number of parasitic ACB eggs by T.dendrolimi was 6.2,and that of the control was 6.8.The results suggested that B.bassiana had no influence on parasitism rate of T.dendrolimi.Secondly,the fungal conidia transmitting process from host eggs to pest bodies was visualized by fluorescence observation with GFP labeled B.bassiana strain.The results showed that there was fluorescence in the treatment group of A.pernyi eggs,T.dendrolimi body,parasitic corn borer eggs,and the pest larvae escaped form parasitism by T.dendrolimi,with carrier rate was 60%,while the control group did not.The number of spores of B.bassiana carried by T.dendrolimi through the hind feet,wings and abdomen was significantly higher than that of the forefoot and head,which is beneficial for B.bassiana spores carrying to the pest larvae surface during the parasitic process.In a screen house test,the muscardine cadaver rate of parasitic pests larvae by TCB was 27.0±5.70%.Compared to T.dendrolimi release only,the control efficiency of number of damaged plants,wormholes,and alive pests increased by 28.1%,22.8%,and 24.5%after TCB treatment in the field application.For muscardine cadaver,no significant difference was achieved between T.dendrolimi release only treatment and control,which were only 1.44 and 1.82,respectively,while it was 9.41 per 100plants in TCB treatment which demonstrated a higher efficiency.At the same time,the dosage of B.bassiana was 0.7 g/ha,which was negligible compared with the field control amount of 500 g/ha.To sum up,this study established a high efficient system for carrying of B.bassiana by T.dendrolimi.Field experiments show that TCB can significantly improve its control effect against ACB,greatly reduce the amount of B.bassiana and save manpower.TCB realized synergy of the two biocontrol agents. |
