THE INFECTIVITY OF SFMNPV ON FALL ARMYWORM IS INFLUENCED BY THE HOST PLANT

ABSTRACT - This work evaluated the infectivity and production of occlusion bodies (OBs) of the SfMNPV-6NR on fall armyworm (FAW), Spodoptera frugiperda , when fed on different host plants. The experiment was performed in laboratory, in a completely randomized design using two concentrations of SfMNPV-6NR (2×106 and 2×107 OBs/mL) and six different host plants (soybean, corn, cotton, bean, sorghum and millet). The larval mortality, larval weight (LW), pupal weight (PW) of S. frugiperda and the production of OBs by virus were evaluated. S. frugiperda larvae were less susceptible to baculovirus when fed on cotton leaves (38 ± 4.17 and 70 ± 6.44% mortality) in the two concentrations tested (2×106 and 2×107 OBs/mL, respectively). The LW was affected by the virus concentration depending on the plant species consumed and the virus concentrations. The PW was affected by the plant species used to feed larvae. There was no effect of the host plant on the OBs virus production. The results demonstrate adverse effects of the host plant on the infectivity of the SfMNPV-6NR in S. frugiperda , especially a deleterious effect of the cotton plant in the virus infection capacity. Keywords: Fall armyworm, entomopathogenic virus, tritrophic interaction, plant host, cotton. A INFECTIVIDADE DE SfMNPV SOBRE A LAGARTA-DO-CARTUCHO E INFLUENCIADA PELA PLANTA HOSPEDEIRA RESUMO – Este trabalho avaliou a capacidade de infeccao e producao de corpos de oclusao (CO) de SfMNPV- 6NR sobre a lagarta-do-cartucho, Spodoptera frugiperda , quando alimentada em diferentes plantas hospedeiras. O experimento foi realizado em laboratorio, em delineamento inteiramente casualizado, utilizando duas concentracoes de SfMNPV-6NR (2×106 e 2×107 CO/mL) e seis diferentes plantas hospedeiras (soja, milho, algodao, feijao, sorgo e milheto). Foram avaliados a mortalidade larval, o peso de larvas mortas (PL), o peso de pupa (PP) e a producao de CO do virus. As larvas de S. frugiperda foram menos suscetiveis ao baculovirus quando alimentadas com folhas de algodao, apresentando as menores taxas de mortalidade (38 ± 4,17 e 70 ± 6,44%) com as duas concentracoes testadas (2×106 e 2×107 CO/mL, respectivamente). O PL foi afetado pela concentracao de virus, dependendo da especie de planta consumida e concentracao de virus testada. O PP foi afetado pela especie de planta com a qual as larvas foram alimentadas. Nao houve efeito da planta hospedeira na producao de CO do virus. Nossos resultados demonstram um efeito adverso da planta hospedeira sobre a infectividade do virus em S. frugiperda , especialmente um efeito deleterio da planta de algodao na capacidade de infeccao do virus. Palavras-chave: lagarta-do-cartucho-do-milho, virus entomopatogenico, interacao tritrofica, planta hospedeira, algodao.