ROOT-KNOT NEMATODE MANAGEMENT IN DRYLAND TARO WITH TROPICAL COVER CROPS

Twenty-two cover crops were evaluated for their ability to reduce dama ge by root-knot nematode, Meloidogyne javanica, to taro, Colocastia es culenta, in a tropical cropping system. Cover crops were grown and inc orporated into the soil before tare was planted. Barley, greenpanic, g lycine, marigold, sesame, sunn hemp, and sorghum x sudangrass DeKalb S T6E were poor or nonhosts to the nematode as measured by low populatio n changes of nematodes in soil between cover crop planting and tare pl anting. Alfalfa, buckwheat, cowpea, lablab, Lana vetch, mustard, oat, okra, rhodes grass, ryegrain, ryegrass, siratro, sweet corn, and wheat allowed nematode populations to increase dramatically. Tare yields we re greatest in the marigold plots and lowest in the ryegrain plots. Ta re corm weight decreased with increasing initial nematode population ( Pi) (r = 0.22, P = 0.056). Siratro, ryegrass, and Blizzard wheat plots had higher tare yield than plots with similar Pi's but planted to oth er cover crops. These cover crops may have antagonism to other soil mi croorganisms or their decomposition products may be toxic or adversely affect the nematodes. Cover crops can be an effective and valuable ne matode management tactic for use in minor tropical cropping systems su ch as tare.