Development of bioinsecticide based on Streptomyces griseoflavus PAL114 for control of black bean aphids Aphis fabae

Abstract

ABSTRACT This research highlights the efficiency of a bioinsecticide based on Streptomyces griseoflavus PAL114 in controlling black bean aphids and its effect on fava beans. Three actinobacterial strains were tested in vitro for their aphicidal activity. The PAL114 strain was then formulated in talc powder and tested again. Formulation processes were performed with four spore suspension densities (102, 104, 106 and 108 spore ml−1) at a rate of 25 ml per 100 g of talc powder. Furthermore, the in vivo effect of bioinsecticide on fava bean plants was studied in pot experiments using two application methods: spray and spray + soil amendment. The results showed that only the PAL114 strain had a highly significant effect on mortality (p = .001). Their high-density formulations at 106 and 108 spore ml−1 induced very highly significant activity (p < .001) for both, with no influence difference exceeding 90% after 58 h. In contrast, the other low-density formulations at 102 and 104 spore ml−1 had no significant effect (p = .322 and p = 1.000, respectively). There was no adverse effect of the bioinsecticide on fava bean; instead, there was an improvement in growth, especially when the spray application was combined with soil amendment. The present study opens up prospects for field studies on the biocontrol of this crop pest.