Effects of biopesticides on developmental biology of Fall armyworm (Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) in maize crops in Morogoro, Tanzania

Abstract

The Fall armyworm (Spodoptera frugiperda (J.E. Smith), is a highly mobile and polyphagous herbivore threatening crop production and the livelihoods of millions of smallholder farmers in the newly invaded areas in Africa, including Tanzania. 353 host plant species, principally Poaceae (maize, sorghum, rice, wheat, sugarcane, millet), Asteraceae (sunflower), Malvaceae (cotton), Fabaceae (soybean), families, groundnuts, potatoes, several fruit trees, ornamental plants, weed species, and vegetable crops are also hosts to FAW. This study aims to determine the effect of biopesticides on the developmental biology of FAW. A completely randomized design (CRD) was used to establish an experiment involving biopesticides; Bacillus thuringiensis Bt, Metarhizium anisopliae and Azadirachta indica seed extract each applied at a lower dose of 2 millimeters, 2 millimeters and 30gram per liter of water respectively, and tested against FAW in the laboratory. Each treatment was replicated four times. Results showed the developmental duration of FAW stages differed significantly between treatments. The time for each growth stage; egg incubation, larval, pupation and the total developmental were significantly longer (p < 0.001) in the biopesticidestreated colony compared to the untreated ones. The shortest developmental duration of FAW stages was observed on control colonies at 2.1 ± 0.18, 14.88 ± 0.18, and 27.7 ± 0.34 days for egg, larva and pupa stages respectively. The longest developmental duration of 3.5 ± 0.37, 22.03 ± 0.59, 12.68 ± 0.23 and 37.7± 0.54 days for egg, larva and pupa stages respectively was observed in colonies under B. thuringiensis treatment. These results confirmed that biopesticides can work effectively to keep FAW levels under control. Therefore, these are promising biocontrol alternatives to be included in the integrated pest management scheme.