Control of fall armyworm with Spodoptera frugiperda multiple nucleopolyhedrovirus in sweet corn cultivated under agroecological conditions

The fall armyworm (FAW), Spodoptera frugiperda (JE Smith) is a polyphagous pest documented on more than 80 plant species. In vegetable production systems, sweet corn is their preferred host, but also infests other plants such as chilli, tomato, pumpkins, cucumber, beans and eggplant. Control strategies are commonly carried out by the use of chemical insecticides even though resistance of S. frugiperda populations to several insecticides has been reported. Last decades, have registered rapid adoption of organic and agroecological practices in horticulture, particularly those that rely on bioinputs such as biopesticides and biofertilizers. The baculovirus Spodoptera frugiperda Multiple Nucleopolyhedrovirus (SfMNPV) is a pathogenic agent for the fall armyworm and an alternative tool used for its control in sustainable pest management strategies. In this work, we evaluate two indigenous SfMNPV-based liquid formulations sprayed on sweet corn cultivated under agroecological conditions. Larvae fed with leaves treated with SfMNPV OBs showed mortality rates ranging from 55 to 68 %. Offspring from adult surviving to OBs treatments was analyzed by PCR and the results confirmed sublethal infections and vertical transmission in the fall armyworm. Corn ears harvested from each treatment were individually observed for insect presence, where the lowest rate of fall armyworm per corn ear was registered in plants treated with SfMNPV OBs. Analysis of secondary plagues in corn ears identified the sap beetle Carpophilus dimidiatus and the maize-infesting fly larvae Euxesta mazorca as the most abundant insect pests. These results show that indigenous isolates of SfMNPV produce a significant control on FAW under agroecological conditions, suggesting that the use of formulations including this virus might be a valuable tool for pest management in sustainable vegetable production systems.