Effect of starvation and feeding on desiccated cover crops (Urochloa spp.), in different time periods, on the survival and biomass of Spodoptera frugiperda

Abstract

In tropical agroecosystems, cover crops are an alternative toward a more diverse and sustainable production. Urochloa spp. (syn. Brachiaria spp.) are perennial grasses that are commonly used as cover crops in the no-tillage crop systems. Their residues after desiccation protect the soil and provide nutrient to the next crop cycle. However, these plants can act as a green bridge to fall armyworm (FAW) during the winter season. When summer crops are sown, late instar larvae destroy the seedlings. Therefore, one of the main issues in the management of cover crops is when to perform desiccation before the main crop sowing to avoid FAW larvae survival on the straw. In this context, we investigated the survival of S. frugiperda larvae under different starvation time periods, and assessed their survival and biomass on U. ruziziensis (Ur) and U. brizantha (Ub) desiccated over different time periods. Our results showed that FAW larvae developed into pupae only when corn was offered for twelve days and during the total larval phase. However, larvae fed for eight days survived approximately 13 days. Larval survival decreased on Ub and Ur with increasing infestation time after desiccation. However, survival was higher on Ur. Also, larval biomass was lower on Ub at 7, 14 and 21 days after desiccation. The results obtained may have direct implications for FAW management.