Management of Meloidogyne hapla on Lettuce in Organic Soil with Sudangrass as a Cover Crop.

Host suitability for Meloidogyne hapla of six cover crops was tested in the greenhouse. Sudan-grass cv. Trudan 8 and rye (mixture of cultivars) were nonhosts; oat cv. Porter was a poor host; and phacelia cv. Angelia, oilseed radish cv. Renova, and yellow mustard cv. Martigena were maintenance hosts. When incorporated as a green manure before planting of lettuce cv. Mon-tello, sudangrass was the most effective of the cover crops in reducing egg production of M. hapla. Soil amendment with all parts of sudangrass resulted in lower reproduction of M. hapla on lettuce than soil amendment with only roots of sudangrass. Soil incorporation of 2-month-old (or younger) tissues of sudangrass was more effective in reducing nematode reproduction on subsequent lettuce plants than incorporation of 3-month-old tissues. Sudangrass was grown as a cover crop after lettuce for three growing seasons in field microplots and incorporated as a green manure before the first fall frost. Weight of lettuce heads was significantly higher and reproduction of M. hapla was significantly lower in sudangrass-amended microplots compared with those left fallow between lettuce crops, but results varied with year and nematode infestation level.