Host suitability of potential cover crops for root-knot nematodes

Several potential cover crops were evaluated for their susceptibility to Meloidogyne arenaria race 1, M. incognita race 1, and M. javanica in a series of five greenhouse experiments. No galls or egg masses were observed on roots of castor (Ricinus communis), cowpea (Vigna unguiculata cv. Iron Clay), crotalaria ( Crotalaria spectabilis), or American jointvetch (Aeschynomene americana). Occasional egg masses (rating less than or equal to 1.0 on 0-5 scale) were observed on marigold (Tagetes minuta) in one test with M. incognita, on sesame (Sesamum indicum cv. Paloma) in a test with M. arenaria, and on sunn hemp (Crotalaria juncea cv. Tropic Sun) in 1 of 2 tests with M. incognita; otherwise, these crops were free of egg masses. Numbers of second-stage juveniles (J2) hatched from eggs per root system were low (less than or equal to 10/pot) for the above mentioned crops. Egg-mass levels and numbers of hatched J2 of M. incognita on pearl millet (Pennisetum typhoides, Tifleaf II hybrid) were comparable to those on a susceptible tomato (Lycopersicon esculentum cv. Rutgers). In a test with M. arenaria, egg mass levels and numbers of J2 on Japanese miller (Echinochloa frumentacea) were similar to those on tomato. Japanese miller was susceptible to each of the nematode isolates tested. However, several of the crops evaluated were very poor hosts or non-hosts of the nematode isolates, including several legumes (cowpea, crotalaria,jointvetch, sunn hemp) that have potential use in both nematode and nitrogen management.