Root knot nematode infection on both cotton and tomato cultivars normally resistant to fungal wilt can predispose these plants to severe Fusarium wilt infection. In the southern San Joaquin Valley, especially in Kern County, joint infection of Meloidogyne incognita and Fusarium oxysporum f. sp. vasinfectum can severely damage Acala cotton. Galled okra and tomato roots infected with M. incognita are highly susceptible to infection by Rhizoctonia solani, a disease complex that results in root decay caused by the fungus within about one month after nematode infection. This interaction is common in the warm irrigated soils of California's interior valleys. The fungus Rhizoctonia solani and the root lesion nematode P. minyus have been closely and consistently associated with natural infections of winter wheat in the Pacific Northwest that result in root rot, yellowing, stunting, and yield reduction of the crop. Similar associations between fungi and nematodes have been found to cause brown rot of tobacco. Disease associations between Verticillium species and Pratylenchus penetrans have been recorded on eggplant, mint, and tomato from other states. Associations of nematodes with bacteria also occur but are less common. An example is the foliar nematode Aphelenchoides ritzemabosi and Corynebacterium tumefasciens joint infection that causes "cauliflower" disease on strawberries not common to California.
From: McKenry, M.V. and P. A. Roberts. 1985. Phytonematology Study Guide. University of California, Division of Agriculture and Natural Resources. Publication 4045.