Abstract
The root-knot nematode ( Meloidogyne spp.) is an obligate plant parasite and is one of the largest threats to the Australian sweetpotato industry, causing crop losses of up to 57% of marketable yield. In this study, two potential fungal biocontrol agents were encapsulated in alginate granules and their nematophagous activity was assessed in a laboratory-based microcosm experiment. Both species of fungi significantly reduced numbers of root-knot nematodes in red ferrosol soil. A greater reduction was observed in untreated field soil prior to introduction of root-knot nematodes and fungal biocontrol agents compared to soil that had been heat-sterilised. In a ten-week glasshouse experiment, no significant difference in the root-knot nematode populations in sweetpotato roots and soil was found between fungal biocontrol agent and control treatments. There was a trend towards an increase in the sweetpotato storage root weight and reduction in storage root damage in fungal biocontrol agent compared to control treatments, and both yield and damage levels were similar to those achieved from the use of chemical nematicide treatments. These results demonstrate the need for greater understanding of the interactions between soil biological populations and introduced nematophagous fungi if effective biocontrol is to be consistently achieved with these bioagents under field conditions.