Rotations With Crotalaria Spp. Do Not Suppress Populations Of Meloidogyne Incognita In Cotton

Field studies were conducted in Mato Grosso, Brazil and Georgia, USA to evaluate the efficacy of Crotalaria spp. as a rotational cover crop for managing Meloidogyne incognita in cotton (Gossypium hirsutum). The two studies differed in how Crotalaria spp. were incorporated into the cotton production system to reflect differences in climate (tropical vs subtropical) and production systems typical for the two regions. In Mato Grosso, Crotalaria juncea and C. spectabilis were planted after soybean in late summer, grown for approximately 300 days, and incorporated into the soil 6-15 days prior to cotton planting. In Georgia, C. juncea and a nematode-resistant cowpea, Vigna ungiculata, were planted after maize in the late summer, grown until killed by frost in the early winter, and cotton was planted in the next season. Soil population densities of M. incognita and root galling in cotton were similar in cotton following either fallow, resistant cowpea, or Crotalaria spp. However, Crotalaria spp. significantly increased cotton plant height at the time of harvest relative to the other treatments. Except for one of the experiments in Brazil, incorporation of Crotalaria spp. in the rotational scheme did not increase cotton yield. Results indicate that a cover crop of Crotalaria spp. does not suppress M. incognita in cotton production system more than a fallow period or planting a resistant cover crop.