Fungal Biocontrol Delivery Systems for Nematodes

After isolation, antagonists of nematodes have to be developed for biocontrol. The first step usually involves a screening program including traits relevant to the performance of these organisms in the field. Root colonization is considered as an important ability for biocontrol of plant-parasitic nematodes (Bourne et al. 1996). Evaluation of pathogenicity, especially to nematode eggs, is difficult since these stages are nonmotile. Several techniques have been used for this purpose (Gunasekera et al. 2000; Irving and Kerry 1986; Lopez-Llorca et al. 2002b). Once fungal antagonists have been rated, promising strains should be stored in a safe way. To this respect, an assessment of the existing methods of fungal preservation on nematophagous fungi should be carried out.

Stirling and colleagues developed formulations of nematophagous fungi for use in laboratory (Stirling et al. 1998a,b) and field experiments (Stirling and Smith 1998). Control of root-knot nematodes was achieved in microcosms, but not in the field. The authors stressed that formulations with greater activity should be developed for field experiments. Other factors than formulation design could also be responsible for poor performance of BCAs in the field. Soil microfauna, e.g., enchytraeids (Jaffee 1999) and nematodes, have been found to consume the nematophagous fungi inoculum. Soil receptivity to inoculum of nematophagous fungi should be assessed before delivery of large amounts of inoculations are to be carried out (Wakelin et al. 1999).

The effects of nontarget organisms beneficial to the crop rhizosphere, e.g., mycorrhizal fungi and rhizobacteria, on nematophagous fungi have not yet been characterized. Such studies would improve the design of synergistic methods of approaching biocontrol of root diseases caused by nematodes and other pathogens.

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