Effect of tropical rotation crops on Meloidogyne incognita and other plant-parasitic nematodes

In a field experiment conducted on sandy soil in Florida during the 1993 season, rotation crops of castor (Ricinus communis), velvetbean (Mucuna (deeringina), 'Mississippi Silver' cowpea (Vigna unguiculata), American jointvetch (Aeschynomene Americana). 'Deltapine 51' cotton (Gossypium hirsutum), and 'SX-17' sorghum-sudangrass (Sorghum bicolor X S. sudanense) were effective in maintaining low population densities (< 12/100 cm3 soil) of Meloidogyne incognita race 1, whereas high population densities (> 450/100 cm3 soil) resulted after 'Clemson Spineless' okra (Hibiscus esculentus) and 'Kirby' soybean (Glycine max). Following a winter cover crop of rye (Secale cereale), densities of M. incognita following the six most effective rotation crops (1993 season) remained relatively low (less than or equal to 32/100 cm3 soil) through midseason of an eggplant (Solanum melogena) crop planted in 1994, but increased by the end of the eggplant crop. The rotation crops planted during 1993 had little effect on yield of eggplant in 1994. Eggplant yield was inversely correlated with preplant densities (Pi) of Belonolaimus longicaudatus (r = -0.282; P less than or equal to 0.10; 46 df), but not with Pi of M. incognita. A separate microplot experiment conducted in 1994 revealed that final densities (Pf) of M. incognita race 1 following 13 different crop cultivars were lower (P less than or equal to 0.05) than Pf following a 'Pioneer X304C' corn (Zea mays) control, but only 'Mississippi Silver' cowpea and 'Sesaco 16' sesame (Sesamum indicum) resulted in lower (P less than or equal to 0.05) Pf of Paratrichodorus minor than the corn control. It is critical that rotation crops intended for suppression of individual Meloidogyne spp. be evaluated for their response to other nematode pests as well.