Effects of Cowpea and Maize Root Leachates on Meloidogyne incognita Egg Hatch.

Nematode egg hatch is an important phase in the life cycle (1). Factors that influence this process may have a highly significant effect upon the survival of the nematode, its generation time, and its ability to incite disease. Root diffusates and seasonal changes in environmental, physical, and chemical factors that are related to diapause in unhatched larvae affect the hatching of plant-parasitic nematode eggs (1,7,8). The effects of root diffusates on egg hatch are difficult to assess under multiple cropping systems common in the tropics (6). I f plant-parasitic nematode eggs are induced to hatch by root diffusates of component crops, then this aspect of the cropping system could be incorporated into a management strategy. Cowpea (Vigna unguiculata (L.) Walp) and maize (Zea mays L.), are common components of cropping systems in southwestern Nigeria. Cowpea is a good host ofM. incognita, whereas maize is a poor host (5,9). This study was carried out to compare, singly and in combination, the in vitro effects of root leachates collected from cowpea and maize on egg hatch ofMeloidogyne incognita (Kofoid and White, 1919) Chitwood, 1949. A population of M. incognita race 2 was reared in a screenhouse on cowpea 'Ire Brown.' Seedlings of Ife Brown and maize