不同条件下几种虫生真菌对棉铃虫的侵染致病效应

Pathogenicity of several fungal species on Helicoverpa armigera in different conditions

用 5种真菌共 10个菌株 ,分别对不同虫龄和生理状态的棉铃虫幼虫 ,采用不同的孢子剂量 ,设置不同的温度进行了毒力测定 ,结果表明 :(1)球孢白僵菌和莱氏野村菌两个菌种对棉铃虫有明显的防治效果 ,且前者优于后者 ;在白僵菌中 5 S0 3菌株毒力最高 ,对棉铃虫 1- 2龄幼虫的致死中时 (L T50 )为 6 .70 - 7.0 2 d,校正死亡率为 86 .96 % - 91.30 % ,僵虫率为 2 0 .0 0 % - 36 .6 7%。 (2 )同一菌株对不同生理状态的棉铃虫毒力差异显著 ,刚脱皮幼虫极易受感染 ,僵虫率高达 85 .71% ,;同一菌株 (5 S0 3)对棉铃虫 1- 2龄与 3- 4龄幼虫的校正死亡率相差 35 %以上 ,L T50 相差 4 d多 ,低龄幼虫较为敏感。 (3) 5 S0 3防治棉铃虫的最适浓度为 7.8× 10 7孢子 / m l,最适温度为 2 0 - 2 5℃。

Virulence of the five fungal species (total 10 strains) to H.armigera larvae was tested by setting up different conidial doses and temperature conditions. The results showed as follows: (1) Virulence of different fungal species and strains was various. Beauveria bassiana and Nomuraea rileyi had obvious controlling efficacy to H.armigera, and the former is prior to the latter. Virulence of the B.b strain 5S03 to H.armigera was the highest, the LT 50 for the 1st and 2nd instar larvae was about from 6.70 to 7.02 days, with adjusted death rates from 86.96 to 91.30 percent and muscardine cadaver rates from 20.00 to 36.67 percent.(2) The difference of virulence of the same strain was extremely obvious for different physiological condition and different instar larvae, the new ecdysial larvae were subject to injecting, the muscardine cadaver rate reached at 85.71 percent. The young instar larvae were more sensitive, and the difference reached at more than 35 percent for adjusted death rates and more than four days for LT 50 compared with the old instar larvae.(3)The most suitable density of 5S03 to control H.armigera was 7.8×10 7 conidia/ml, and temperature was from 20 to 25 ℃.