Dose-dependent prevention of maize damage through the application of entomopathogenic nematodes against the fall armyworm

Abstract: Novel formulations of entomopathogenic nematodes (EPN) have been developed as
biological control solutions against the caterpillars of the invasive alien fall armyworm,
Spodoptera frugiperda, on maize. We evaluated the dosage of EPN needed to manage the maize damage at sufficient levels under real farming conditions. We implemented, together with local farmers and seasonal workers, six dose-response field plot trials in Rwanda. Dosage of 375 up to 12000 EPN were applied as a fluid gel spray into the leaf whorls. All dosages above 1500 EPN per whorl effectively mitigated severe damage caused by armyworms, with the highest dose (12000 EPN) being the most effective. However, repeat treatments were found to be needed in maize fields with continuous re-infestations, doubling or even tripling the effects of EPN per additional spray. Other formulations (e. g., gels, UV protectants) or application techniques warrant further investigation to increase the efficacy of EPN. The ultimate goal is to provide safe alternatives to the frequently used insecticides.