甘肃省三种昆虫病原线虫的生物学特性及其对番茄潜叶蛾的致病力测定OA

[Aim]To clarify the biological characteristics of entomopathogenic nematodes in Gansu Province,Northwest China and their control efficacy against Tuta absoluta,and to lay the foundation for the development and application of local entomopathogenic nematode resources.[Methods]Three entomopathogenic nematode species with high virulence against lepidopteran insects identified through preliminary screening(Steinernema feltiae 0956L,Steinernema hebeiense 0847H and Heterorhabditis megidis 0863Y)were used for the study.Through indoor bioassays,the fecundity of the three nematode species was determined,and the virulence of different infection doses(60,120,180,240 and 300 IJs/ind.)of nematodes and nematode species to Galleria mellonella larvae,and the effects of environmental temperature(15,20,25,30 and 35 ℃)and humidity(moisture content of fine sand 1％,2％,5％,10％and 15％)on their virulence were systematically observed and measured.Additionally,the tolerance of the nematodes to high temperatures(36,38 and 40 ℃)and low humidity(50.5％)stress was observed and determined.The virulence of the three nematode species at different infection doses(5,10,20,30,40 and 50 IJs/ind.)to the 3rd instar larvae of T.absoluta was also measured.[Results]H.megidis 0863Y had the strongest fecundity,followed by S.feltiae 0956L,and S.hebeiense 0847H had the least fecundity.The three entomopathogenic nematode species had high virulence to G.mellonella larvae and the optimum infestation dose was 240 IJs/ind.Among them,S.feltiae 0956L showed the most virulence to G.mellonella larvae,causing the corrected larval mortality rate of 97.3％at 96 h post infection at the dose of 240 IJs/ind.,with a faster infection speed than the other two nematode species.The optimum temperature range for S.feltiae 0956L infestation against G.mellonella larvae was 20-25 ℃,while that for S.hebeiense 0847 H and H.megidis 0863 Y infestation against G.mellonella larvae was 25 ℃.The mortality rate of G.mellonella larvae increased with the duration of infestation of all the three nematode species in the range of 1％-15％relative humidity at a constant temperature of 25 ℃,and significantly increased with the increase in moisture content of fine sand.The survival rates of S.feltiae 0956L,H.megidis 0863 Y and S.hebeiense 0847H after 4-h treatment in a water bath at 40 ℃were 15.0％,2.4％and 1.8％,respectively,indicating that S.feltiae 0956L had the strongest tolerance to high temperatures,while H.megidis 0863Y and S.hebeiense 0847H had weaker tolerance to high temperature.After 48-h low humidity(50.5％)stress at 25 ℃,S.feltiae 0956L had a lower survival rate of 72.87％,and had weaker ability to resist the low humidity stress than the remaining two nematode species,but its resuscitated nematode caused the highest mortality rate to G.mellonella larvae(73.33％),and the rate of decrease in infectivity was the smallest(21.43％).All the three nematode species exhibited high virulence to larvae of T.absoluta,and the optimum infestation dose was 40 IJs/ind.Among them,S.feltiae 0956L demonstrated the strongest virulence to larvae of T.absoluta,causing the corrected larval mortality rate of 86％at 60 h post infection at the dose of 50 IJs/ind.H.megidis 0863Y and S.hebeiense 0847H exhibited weaker virulence to larvae of T.absoluta,causing the corrected larval mortality rates of 66％and 62％,respectively,at 60 h post infection at the dose of 50 IJs/ind.[Conclusion]The three entomopathogenic nematode species S.feltiae 0956L,S.hebeien.se 0847H and H.megidis 0863 Y collected from Gansu Province exhibit strong fecundity and high virulence to T.absoluta larvae,demonstrate good adaptability to high temperatures and low humidity stress,as well as show good control efficacy against T.absoluta larvae.Among them,S.feltiae 0956L possesses significant potential for biological control.