Biocontrol Efficacy Of Entomopathogenic Nematode Against Larvae Of Tobacco Grubs

Grubs are one of the most important ground pests all over the world which feed on roots and stems that have a serious damage to crops.Yunnan Province has a large amount of occurrence on grubs.Entomopathogenic nematode(EPN)as a late-model biologic agent which has the advantage of specificity for host,safety for human and livestock is widely use for biological control.This paper reported the control effect of Steinernema longicaudum X-7 to the grubs on tobacco in Yunnan Province.The main results as follows:Choose the best control effect on grubs from Steinernema scarabaei,Steinernema carpocapsae All,Steinernema longicaudum X-7 and Steinernema glaseri.After treated with 5ml,500IJs/ml EPN on grubs,results showed Steinernema longicaudum X-7 was the best choice,the grubs mortality were 76.67%.When use the filter paper as medium,treated 5ml,640Ijs/ml S.longicaudum X-7 preparation,the grubs mortality were 86.67%.The pot experiments showed that after treated 10 ml,1600IJs/ml S.longicaudum X-7 preparation twice,the survival rate was 13.33%,the pest population control index was 0.2854.In order to eliminate influence of abiotic stress on S.longicaudum X-7 nematode,temperature and UV-B radiation tests showed that when the temperature blow 40?,over majority nematodes survived and they could survive after 41 ? in 1 hour,almost all died when the temperature over 42?.UV-B radiation has influence on its survival,more than 20 min below 20 W UV-B radiation,the nematodes started to died.With the increase application times of Steinernema longicaudum X-7 in field 1,the seeding rate and grub population density was decreased gradually,the growth state of tobacco plant increased gradually.Treated Steinernema longicaudum X-7 20000 IJs every tobacco seeding three times at the 1 week before tobacco planting,the day of tobacco planting and 3 days after tobacco planting,dropping rate of grub was 65%,survival rate of tobacco seedling was 58.88%.Treated grubs with Metarhizium anisopliae,Beauveria bassiana and S.longicaudum X-7,the results showed that applied S.longicaudum X-7 single,dropping rate of grub was 57.14%,applied Metarhizium anisopliae and S.longicaudum X-7,dropping rate of grub was 58.70%,applied Beauveria bassiana and S.longicaudum X-7,dropping rate of grub was 58.14%,there was no significant difference between the three groups,When applied Metarhizium anisopliae,Beauveria bassiana and S.longicaudum X-7 together,dropping rate of grub was 75.61%,th survival rate of tobacco seeding was 58.88%,the effect of seedling significantly increased.Determine soil microbial biomass by Biology,the greater light absorption value the more microbial biomass.The light absorption value after 120 days since the applied S.longicaudum X-7 is 0.278 and it is larger than the first day wit hout applied.Infer that nematode could alive in Yunnan for about 120 days.