Second crop options for Pratylenchus brachyurus management on soybean

Abstract

The lesion nematode Pratylenchus brachyurus is a major pest of soybean in Brazil, managed by treating seed with nematicides and replacing corn for pearl millet (Pennisetum glaucum) and rattlepods (Crotalaria spp.) as a second crop. However, these cover crops are not profitable, leading growers to consider alternatives as cowpea, sunflower, and sorghum. In fact, although cowpea and sorghum are susceptible to P. brachyurus, cowpea is widely cultivated in the Brazilian Cerrado, where P. brachyurus is prevalent, and the forage sorghum ‘BRS Ponta Negra’ has been recommended for P. brachyurus management, based on field observations. Considering the increasing importance of cowpea in the Brazilian Cerrado, three pot trials were carried out to evaluate the host status of modern cowpea cultivars for P. brachyurus. Additionally, two pot trials were carried out to evaluate the effect of cowpea, sunflower, forage sorghum ‘BRS Ponta Negra’, pearl millet and showy rattlepod on soybean production in soil with P. brachyurus, taking account the scarcity of studies that prove the benefits of replacing corn for resistant crops on soybean grain production. The five cowpea cultivars tested were highly suitable hosts for P. brachyurus, supporting previous findings. Therefore, cowpea should be avoided in infested growing areas, especially as a second crop after soybean. Among the cover crops, only showy rattlepod consistently decreased P. brachyurus population density and increased soybean grain production, proving to be more effective than pearl millet in managing P. brachyurus.