Potential for biological control of Heterodera schachtii by Pochonia chlamydosporia var. chlamydosporia on sugar beet

Abstract

The biological control potential of an isolate of Pochonia chlamydosporia var. chlamydosporia against Heterodera schachtii was examined by assessing the percentage of females and cysts that became infected on water agar, the effect of culture filtrate on juvenile mobility, and the effects of the fungus on the final population of the nematode on sugar beet under greenhouse conditions. After 3 weeks at 20°C, 74 and 95% of the eggs within cysts and females, respectively, were colonised by the fungus on water agar. The full concentration of the fungal filtrate from cultures in malt extract broth killed only 12% of the juveniles after 24 h at 25°C. In the greenhouse experiment, adding 16,000 chlamydospores of the fungus per gram of soil as either colonised barley grains or spores reduced the final number of females on roots of sugar beet by 50 and 66%, respectively, after 3 months. The reproduction factor was reduced to ×2 in spore-treated soil compared with ×5 in the untreated control, and 18% of the eggs in spore-treated soil were colonised by fungal mycelium. Generally, P. chlamydosporia var. chlamydosporia was more efficient at reducing the nematode population when applied as spores without any substrate than when used as colonised barley grains.