球孢白僵菌松毛虫分离株对家蚕的致病力

长期以来对于释放球孢白僵菌防治松毛虫是否会导致或加重家蚕白僵病一直存在较大争议，并同时影响真菌杀虫剂的应用。为科学评价球孢白僵菌松毛虫分离株对家蚕的致病风险，并保证研究结果的代表性和准确性，本研究共使用南方8省（区）的64株松毛虫分离株和4省（区）的12株家蚕分离株对3龄家蚕进行了3次致病性试验。结果表明，除其中1株松毛虫分离株外，不管是松毛虫分离株还是家蚕分离株，对家蚕都有一定致病性，但差异较大。在3×107孢子/mL 的浓度下，30株松毛虫分离株的平均侵染率10.2%极显著低于8株家蚕分离株的89.6%；在1.5×108孢子/mL的浓度下，34株松毛虫分离株对家蚕的平均侵染率36.4%极显著低于6株家蚕分离株的90.6%；松毛虫分离株在1.5×108孢子/mL浓度下的侵染率极显著高于3×107孢子/mL下的侵染率，而家蚕分离株在两种浓度下无显著性差异。在1.5×108孢子/mL的浓度下4株对家蚕致病力较强的松毛虫分离株的LT50为7.45～8.20 d，平均7.83 d，比6株家蚕分离株LT50（3.43～3.72 d）的平均数3.62 d多4.21 d。根据毒力较强的家蚕分离株B1和B5与毒力最弱和最强的松毛虫分离株D26和D22的致死浓度的比较，家蚕分离株对家蚕的毒力是松毛虫分离株的132～15733倍；根据他们的致死剂量的比较，家蚕分离株的毒力是松毛虫分离株的43～2201倍。这一对比数据充分表明，尽管不同的松毛虫分离株对家蚕的毒力不同，但所有的松毛虫分离株都具有明显的寄主专化性。综合分析表明，我国南方使用白僵菌杀虫剂防治松毛虫在家蚕中诱发流行病的风险很小。

Pathogenicity to Silkworms of Beauveria bassiana Isolates from Pine Caterpillar

There has been a debate on whether the release of pine caterpillar isolates of Beauveria bassiana causes or enhances white muscardine of the silkworm, Bombyx mori. In order to scientifically investing pathogenic risk of pine caterpillar isolates against silkworms, with high representativeness and great accuracy, 64 pine caterpillar isolates from 8 provinces and 12 silkworm isolates from 4 provinces were used against the 3rd instars of the silkworm in pathogenicity tests in 3 batches. The results showed that either pine caterpillar isolates (except for one of them) or silkworm isolates showed some pathogenicity to silkworm, but with great different virulences. At the concentration of 3×107 conidia/mL and 1.5×108 conidia/mL, the average infection rate of pine caterpillar isolates was 10.2%and 36.4%respectively, significantly lower than that of silkworm isolates (89.6%and 90.6%);the average infection rate of the pine caterpillar isolates at 1.5×108 conidia/mL was significantly higher than that at 3×107 conidia/mL, while in silkworm isolates, the average infection rate were almost the same under the same concentrations. The average values of LT50 of 4 pine caterpillar isolates with comparatively more pathogenic to silkworms at 1.5×108 conidia/mL were 7.83 d, longer than that of 6 silkworm isolates (3.62 d). The lethal concentrations of the least virulent silkworm isolates B1 and B5 were 132-15733 times higher than those of the most virulent pine caterpillar isolate D26, D22. The lethal dosages of B1, B5 were 43-2201 times as high as D26, D22. The poignant contrast suggested that although different pine caterpillar isolates had different virulence on silkworms, all pine caterpillar isolates showed obvious host specificity. A comprehensive analysis indicated that the risk of an epizootic induction of white muscardine in silkworms by application of B. bassiana insecticides against pine caterpillars was low.