Management of Soil-Borne Plant Parasitic Nematodes for Sustainable Production of Field Grown Tomatoes by Cover Cropping in Hawaii
Tomatoes and cucumbers are two of the most promising crops for the diversification of Hawaiian agriculture. As with most vegetable crops in Hawaii, they are often severely affected by parasitic nematodes, particularly the root-knot nematode, Meloidogyne incognita and reniform nematode species. Usually, methyl bromide or other soluble nematicides or soil fumigants are used to control these nematodes. Since methyl bromide is being phased out, this project will look at potential cropping practices to control nematodes. The use of intercropping with plants that are either toxic to nematodes or are non-hosts for nematodes have shown good results in experimental trials. This project looks at Sunn hemp (Crotalaria juncea) which is resistant to, and even toxic to, root-knot nematodes and known to be a non-host for the reniform nematode as a cover crop for field grown tomatoes.
Project goals and objectives
Evaluate Sunn hemp (Crotalaria juncea) as a cover crop for field grown tomatoes
To increase the numbers of parasitic nematodes, the test field was first planted with basil, a crop very susceptible to the root-knot nematode. After four months, the field was divided into eight sections and four of these were plowed and planted with Sunn hemp. Basil was left in the other four sections. The nematodes continued to increase in the basil plots but began to disappear in the Sunn hemp plots. Within five months, the differences were statistically significant. The entire field was then plowed and "Merced" variety tomatoes were planted in all of the plots. This variety is susceptible to root-knot nematodes and readily damaged by them. After three months, the differences in nematode populations between the basil and Sunn hemp areas could be seen. The trial clearly showed that Sunn hemp cover cropping significantly reduced soil populations of both the reniform nematode, Rotylenchulus reniformis, and root-knot nematodes and reduced root damage to tomatoes following Sunn hemp.