BIOCONTROL OF HETERODERA-SCHACHTII USING COMBINATIONS OF THE STERILE FUNGUS, STFCH1-1, EMBELLISIA-CHLAMYDOSPORA AND VERTICILLIUM-CHLAMYDOSPORIUM

A sterile fungus, designated as StFCh1-1, and two other fungi, Embelli sia chlamydospora and Verticillium chlamydosporium, isolated from cyst s of the sugar beet cyst nematode, Heterodera schachtii, were tested a s biological control agents against this nematode. The combination of StFCh1-1 with either E. chlamydospora or V. chlamydosporium resulted i n significantly greater impact on the nematode population than any fun gus alone. More females and cysts were colonised by StFCh1-1 than by e ither other antagonist. These nematodes stowed the typical fungal scle rotium on the outside of the body wall, and the hyphal imprint on the inside of the cyst. Few females developed on sugar beet roots in the s oil of those treatments that included the sterile fungus. No juveniles emerged from cysts colonised by the sterile fungus, while some juveni les hatched from eggs within cysts colonised by either E. chlamydospor a or V. chlamydosporium. The density of E. chlamydospora and V. chlamy dosporium in soil, as measured by colony forming unit counts, decrease d over time. Quantification of the sterile fungus in soil was not poss ible using this technique due to rampant growth of saprophytic fungi o n the isolation medium. The results suggest that, despite the promisin g nature of the sterile fungus StFCh1-1 in comparison with the two oth er fungi used, a carefully combined inoculum could still be more effec tive at controlling H. schachtii. The results are discussed in the con text of compatibility of these organisms.