Study shows adult black soldier flies' susceptibility to Beauveria bassiana, necessitating closed facilities

A Protix laboratory study, conducted together with researchers from the University of Copenhagen and published in the Journal of Insects for Food and Feed in 2020, demonstrates for the first time that adult black soldier flies are susceptible to the biocontrol agent Beauveria bassiana. The results show that both a lower and a higher concentration of the fungus had significant effects on mortality and egg count, indicating the need for closed facilities for insect farming to eliminate contamination risks when B. bassiana is applied as a biological control agent close to black soldier fly production facilities.

In the study, we developed a bioassay method and demonstrated that adult flies are susceptible to the fungus B. bassiana (strain KVL 03-122) at both concentrations of 10^5 conidia/ml and 10^8 conidia/ml. Results show that both the lower and higher concentrations had significant effects on mortality in the adult flies, ranging from 36% to 96%, respectively.

Furthermore, healthy flies interacting with deceased flies, spore-contaminated drinking water, or spore-contaminated cages could be at a greater risk of infection than through vertical transmission via mating, as females typically mate only once. Females contaminated with spores could also contaminate the oviposition sites, where other females may lay their eggs.

However, more field-realistic studies still need to be conducted, including the determination of the minimum concentrations of spores required for such infections. Companies must prioritize good hygiene in their facilities, preferably using closed systems and batch-wise production. While manual cleaning is the current standard practice in most cases, publicly available sources indicate that companies are also developing automated cage systems for black soldier fly mating that are capable of self-cleaning between mating cycles.