Improving suppression of Meloidogyne spp. by Purpureocillium lilacinum strain 251

Abstract

The fungus Purpureocillium lilacinum (syn. Paecilomyces lilacinus) is marketed for control of plant-parasitic nematodes in several countries. Our objectives in this study were to determine whether suppression of Meloidogyne spp. by P. lilacinum strain 251 was affected by the crop plant and whether growing winter cover crops such as rye and crimson clover would improve suppression of M. incognita on cotton by the fungus. All experiments were conducted in a glasshouse using non-sterilised field soil. To determine the relative efficacy of P. lilacinum on cotton (Gossypium hirsutum), peanut (Arachis hypogaea) and maize (Zea mays), four concentrations of P. lilacinum (NemOut™) were applied in furrow: 336, 252, 168 and 0 g ha−1. Although the fungus reduced numbers of eggs of Meloidogyne spp. on all crops, percentage suppression was lower on maize than on cotton and peanut at all inoculum levels of P. lilacinum. When rye and crimson clover were grown in pots for 30 days and then killed with a herbicide prior to applying P. lilacinum and M. incognita and planting cotton, the fungus failed to suppress numbers of nematode eggs when the surface residues of the cover crops were removed. However, when the residues were left on the soil surface, percentage suppression (49% for clover and 63% for rye) was greater than when the soil was left fallow (36%). The residues could have created conditions that were more conducive than bare soil to the fungus, such as lower soil temperatures and increase moisture retention.