Combination of nematodes, Sesbania rostrata, and rice: the two sides of the coin
1994
Prot, J.C. (International Rice Research Inst., Los Banos, Laguna (Philippines))
Rice root nematodes are not the only nematode pests of rice. More than 200 species of plant-parasitic nematodes have been reported to be associated with rice. Among these, the root-knot nematodes, Meloidogyne spp., are major pests of rainfed rice, causing swelling and galls throughout the root system. Although they do not cause specific symptoms on the above ground parts of the plant, they can cause severe growth reduction, chlorosis, wilting of plants, and 20-70 percent yield reduction in infested fields. M. graminicola, the rice root-knot nematode, is widely distributed in rainfed upland and lowland ricefields in South and Southeast Asia, especially in light-textured soils. It is considered to be an important pest in rainfed lowland areas in India and northeast Thailand. S. rostrata, unfortunately, is a very good host for M. graminicola when grown in nonflooded soils. Cropping it before rice in nonflooded soils infested by rice root-knot nematodes may increase their number tremendously. This increase in M. graminicola may cause increased yield losses, eliminating the benefit expected from cultivating the green manure crop. This is the other side of the coin. S. rostrata had tremendous potential as a green manure crop. Under rainfed conditions, however, it must be used with caution. It is hazardous to grow S. rostrata in rainfed ricefields where M. graminicola is present. Leguminous crops resistant to M. graminicola should be identified as alternative to S. rostrata in rainfed lowland rice areas infested with the nematode
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