Performance of Fall Armyworm Preimaginal Development on Cultivars of Tropical Grass Forages

SIMPLE SUMMARY: Integrated crop systems that intercrop grass forages and grain crops are an important strategy used for increasing crop production and improving nutrient cycling and soil health. However, pests such as the larvae of the insect Spodoptera frugiperda, which is able to feed on uncountable plant species, may become a huge threat to these systems. There is a great diversity of forage grass species and cultivars available for use in these systems, so we investigated whether the insect performed differently on different forage species. The performance of this pest was good in most plants observed, though the pest performed poorly in Panicum maximum ‘Massai’ and ‘Tamani’ cultivars. On other hand, a careful pest management is necessary for Brachiaria brizantha ‘Paiaguás’, ‘Marandu’, ‘Xaraés’ cultivars and Brachiaria ruziziensis, since these plants are more suitable for the development of the pest. ABSTRACT: Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a polyphagous pest species capable of feeding on almost all forage and grain crops, although the food quality for the larvae likely varies among plant species and cultivars. The cultivation of grass forage species with grains has increasingly been adopted in Brazil, within both no-tillage and crop–livestock integration systems. In this study, we evaluated the performance of S. frugiperda larvae on 14 forage cultivars of Brachiaria, Panicum, and Cynodon, which are widely used in integrated cropping systems in Brazil. The biological performance of S. frugiperda varied among the cultivars. The larval survival rates were lower on Panicum maximum ‘Massai’ and P. maximum ‘Tamani’ cultivars. The insects had the highest performance indexes on Brachiaria brizantha ‘Paiaguás’, B. brizantha ‘Marandu’, and B. brizantha ‘Xaraés’ cultivars, followed by Brachiaria ruziziensis, previously proposed as a standard grass forage for comparisons with other species. On P. maximum, the insect had the lowest performance indexes, with values equal to zero when feeding on the P. maximum ‘Massai’ and ‘Tamani’ cultivars. These results will help make management decisions when cultivating grass forage plants in crop production systems in which S. frugiperda infestation is of concern.