Nematode Population Development

Combinations of winter and fall cover crops were evalu­ ated for the management of plant-parasitic nematodes. The winter cover crops examined were rye (Secale cereale) and narrow-leafed lupin (Lupinus angustifolius) and the fall cover crops were soybean (Glycine max), cowpea (Vigna unguiculata), sorghum-sudangrass (Sor­ ghum bicolor x S. sudanense), sun hemp (Crotalaria juncea), and corn (Zea mays). A summer crop of corn was planted in between the winter and fall cover crops. Nematode population densities were determined before and after each cropping season. Both rye and narrowleafed lupin suppressed the population development of Meloidogyne incognita and Pratylenchus spp. during the winter crop season. However, this effect was eliminated after one cropping cycle of the summer crop, corn. During the fall cropping season, plant-parasitic nema­ tode populations increased in general, however, plots previously in winter narrow-leafed lupin had higher population densities of M. incognita than plots that had winter rye (P = 0.05). All the fall cover crops tested had lower M. incognita levels than corn (P = 0.05). Sorghum­ sudangrass and corn supported the highest population densities of Paratrichodorus minor and Mesocriconemella spp. Sun hemp suppressed all the plant-parasitic nema­ todes present including Helicotylenchus dishystera and Pratylenchus spp. as compared to corn (P = 0.05). There­ fore, rye was more effective in the winter, whereas sun hemp, ‘Iron Clay’ cowpea, and ‘Hinson Long Juvenile’ soybean have good potential as fall cover crops for nematode management.