Non-chemical Approaches for Reducing Plant Parasitic Nematodes in Edible Ginger fields in Hawaii
Hawaii's tropical climate and year-around growing conditions allow plant parasitic nematodes such as Pratylenchus spp., Melodidogyne spp., Radopholus similis, and Anguina spp. To develop throughout the year. Weeds growing on fallow land are often suitable hosts of these nematodes and allow populations to develop even before a crop is planted. The edible ginger root growers are particularly at risk to losses from plant parasitic nematodes. Damage increases labor costs, reduces marketability and, in extreme cases, creates an unmarketable crop. Growers in Hawaii have few registered nematicides to chose from and will lose methyl bromide by 2005. Metam-sodium (Vapam) can also be used but it is not as effective as methyl bromide and highly toxic to fish and other non-target organisms. This project evaluates six cover crops as non-chemical methods for the reduction of plant-parasitic nematodes in edible ginger: marigolds (Tagetes spp., Tagetes ploynema and Tagetes patula, "Sparky"), Sunn hemp (Crotalaria juncea), black oats (Avena strigosa "soil saver'), sorghum (Sorghum vulgare "Sweet BEC Sterile II"),and macuna (Macuna pruriens). The cover crops were compared to treatments with Vapam HL and methyl bromide fumigation. Over all, Sunn hemp was the most promising cover crop.
Project goals and objectives
1). Conduct tests with six cover crops in both field and containerized growing conditions to determine the efficacy of the crop against plant-parasitic nematodes
2). Develop and transfer to Hawaii's growers a management strategy based on the results of efficacy testing.
Sunn hemp showed the most promise as a potential cover crop treatment to reduce nematode damage in ginger production. It was readily adaptable to standard grower practices and produced a yield of No. 1 ginger that was statistically the same as methyl bromide. However, methyl bromide produced a greater overall yield. Future studies with Sunn hemp as a cover crop prior to ginger production will focus on improving efficacy through changes in cultural practices or length of growing period prior to planting ginger.