The Effect of Green Manure Crops on Plant Parasitic Nematodes in the South African Sugar Industry

Plant parasitic nematodes, Meloidogyne javanica in particular, cause significant yield losses in sugarcane crops in South Africa. The chemicals at present available for nematode control are expensive and potentially detrimental to the environment. It has been reported that various types of crops reduce the numbers of plant parasitic nematodes. Seven green manure crops (sunn hemp, marigold, oats, dolichos beans, velvet beans, forage peanuts and cowpeas), as well as tomato and sugarcane variety N12, were evaluated in a glasshouse trial to assess their susceptibility to M. javanica, as well as their influence on other nematode populations. Initial results indicate resistance of forage peanuts, marigolds and sunn hemp to M. javanica. Cowpeas, dolichos beans and tomato were particularly good hosts. The host status of velvet beans and sugarcane variety N12 differed in inoculated and naturally infested soils. Numbers of Xiphinema elongatum were not affected by any of these crops. Forage peanuts and sunn hemp increased the free-living nematode populations more so than did the other crops.