Effect of integrating cover crops and bionematicides on nematode management in organic zucchini

Summary Integrating cover crops and bionematicides presents a sustainable approach to managing plant-parasitic nematodes (PPN) in organic vegetable production systems. The integration of sunn hemp, Crotalaria juncea (‘Crescent sun’) and sorghum-sudangrass, Sorghum bicolor × S. sudanense (‘Sweet Six BMR’) with bionematicides was evaluated in two locations in central (Gulf Coast Research and Educational Centre – GCREC) and south (Fort Lauderdale Research and Educational Centre – FLREC) Florida for the effectiveness of PPN suppression. Field experiments were conducted with establishing cover crops in each location 3 months before planting organic zucchini on plastic beds equipped with a drip application system used to inject three commercial bionematicides (thyme oil, neem oil and azadirachtin) and the broth culture of Xenorhabdus bovienii bacteria associated with Steinernema feltiae . Cover cropping with sunn hemp and sorghum-sudangrass significantly reduced population densities of root-knot nematodes ( Meloidogyne spp.) at GCREC, whereas only sunn hemp reduced the root-knot nematode population at FLREC. Galling severity on zucchini roots caused by Meloidogyne spp. was significantly lower in azadirachtin and neem oil applications integrated with sunn hemp. The impact of integrating cover crops with bionematicides on other PPN, such as Mesocriconema spp., Nanidorus minor and Hoplolaimus spp., varied among the treatments at both locations. Integrating cover crops with bionematicide applications provided additional control options for zucchini, but the efficacy of different bionematicides depended on the nematode species present in the soil and the cover crop species used. These findings underscore the importance of adaptive nematode management, where control strategies are customised to target the specific nematode populations causing economic damage in each field.