Susceptibility of fall armyworm Spodoptera frugiperda (JE Smith) to microbial and botanical bioinsecticides and control failure likelihood estimation

Description of the subject. The fall armyworm Spodoptera frugiperda (JE Smith) has become one of the most devastating pests of maize and other important economic crops in Africa since 2016. Among the alternatives to chemical insecticides, bioinsecticides are an interesting option that needs to be explored. Objectives. The susceptibility of fall armyworm to seven bioinsecticides available on the West African market was evaluated in Burkina Faso. Method. Bioassays were conducted following the approved IRAC 020 protocol. Results. Spinetoram (LC80 = 85.3 µg·l-1) and spinosad (LC80 = 437.9 µg·l-1) were the most toxic at concentrations below those recommended by the manufacturer, and had control failure likelihoods close to 0%. Bacillus thuringiensis and products based on Azadirachta indica and Carapa procera extracts were less effective (at the manufacturers' recommended doses), even though they showed significant levels of toxicity on young instars. Conclusions. A list of effective bioinsecticides should be communicated for sustainable management of fall armyworm in West Africa.