关键词: 蜡蚧菌, 豆蚜, 生物学特性, 毒力测定, 化学农药

Abstract: 【Aim】Aphids are one of the most destructive pests in agricultural production, causing huge agricultural economic losses every year. In this study, a fungus strain HK-1 isolated from dead aphids was identified, its biological characters were analyzed, and the virulence of its conidia to Aphis craccivora adults and its sensitivity to chemical pesticides were determined, in order to provide a theoretical basis for the large scale production and application of Lecanicillium.【Methods】The HK-1 strain was identified by combining morphological charactersistics with multi-gene analysis. The mycelial growth rate, spore production and spore germination rate of the strain HK-1 were determined by changing the medium, pH, carbon and nitrogen sources, respectively. The lethality and the median lethal time (LT₅₀) of the spore suspension against A. craccivora adults were measured by immersion method. The growth rate method was used to determine the median effective concentration (EC₅₀) of common pesticides against this strain.【Results】The strain HK-1 was identified as Lecanicillium araneicola HK-1. The results of biological characters revealed that L. araneicola HK-1 had better growth, spore production and spore germination on potato dextrose agar (PDA) medium than on other media. L. araneicola HK-1 grew fastest at pH 9.0, and had the most spore production at pH 6.0 and 7.0 and the best sopre germination at pH 6.0. In terms of carbon source utilization, the optimal carbon source of L. araneicola HK-1 was sucrose for growth, sorbitol and maltose for spore production, and mannitol and glucose for spore germination. In terms of nitrogen source utilization, the best nitrogen source for growth and spore germination of L. araneicola HK-1 was beef extract and that for spore production was ammonium chloride. Laboratory virulence assay showed that the cumulative mortality rate of A. craccivora adults caused by 1×10⁸ conidia/mL of L. araneicola HK-1 suspension in 6 d was 61.67%. The LT₅₀ value of L. araneicola HK-1 against A. craccivora adults was 3.35 d, and decreased with the increase of the tested conidial concentration. The EC₅₀ values of 5% acetamiprid EC, 10% nitenpyram EC and 6% kasugamycin WP against L. araneicola HK-1 were 32.01, 3 250.46 and 164.02 μg/mL, respectively. 【Conclusion】 L. araneicola HK-1 isolated from this study has a good biocontrol potential against A. craccivora adults.

Key words: Lecanicillium; Aphis craccivora, biological characters, virulence assay; chemical pesticide