Direct and Indirect Infection Effects of Four Potent Fungal Isolates on the Survival and Performance of Fall Armyworm Larval Parasitoid Cotesia icipe

Abstract

Fall armyworm (FAW), Spodoptera frugiperda, has recently invaded Africa where it is seriously threatening food security. Current management methods rely heavily on synthetic insecticides which are harmful to humans, the environment, and non-target beneficial insects. Cotesia icipe was recently identified as a major FAW-associated indigenous parasitoid causing a high parasitism rate on the pest in Kenya. Previous studies have demonstrated the efficacy of Metarhizium anisopliae ICIPE 7, ICIPE 41, ICIPE 78, and Beauveria bassiana ICIPE 621 against FAW. However, limited information is available on the interactions between these potent isolates and C. icipe. This study therefore assessed direct and indirect infection effects of these fungal isolates on C. icipe, induced 2nd instar FAW mortality, and parasitism rates of the infected C. icipe. Results showed that when C. icipe were directly exposed to dry conidia of the fungal isolates, ICIPE 7 and ICIPE 41 caused the highest (100%) C. icipe adult mortality seven days post-exposure. Both isolates also induced the highest FAW larval mortality of 55% and 53%, respectively. ICIPE 78 recorded the highest parasitism rates after direct infection. In the indirect exposure (fungal-infected FAW larvae exposed to the parasitoid), 1 × 109 conidia mL−1 recorded high C. icipe adult and FAW 2nd instar mortalities for all fungal isolates. This study provides an important baseline for effective fungal-based biopesticides development that could also be used in augmentative biological control. However, further studies are warranted to assess the performance of C. icipe in combination with these potent biopesticides in the field.

Effectiveness of Biorational and Synthetic Insecticides in Controlling Fall Armyworm and Their Effects on the Abundance and Diversity of Associated Natural Enemies

“…The lowest parasitism of S. frugiperda larvae by C. icipe were observed in plots treated with M. anisopliae in 2020A in Wakiso, suggesting that this EPF could have a negative effect on the parasitoid. Whereas M. anisopliae ICIPE 7 and 78 were reported to reduce parasitism by C. icipe [33,34], we did not observe this because of the low abundance of parasitoids in the seasons when we used the two products. Further observations will thus be needed to conclude on the effects of the two EPFs on parasitism of S. frugiperda by the different parasitoids.…”

Biorationals and Synthetic Insecticides for Controlling Fall Armyworm and Their Influence on the Abundance and Diversity of Parasitoids

“…The lowest parasitism of S. frugiperda larvae by C. icipe was observed in plots treated with M. anisopliae in 2020A in Wakiso, suggesting that this EPF could have a negative effect on the parasitoid. Whereas M. anisopliae ICIPE 7 and 78 were reported to reduce parasitism by C. icipe [32,33], we did not observe this because of the low abundance of parasitoids in the seasons in which we used the two products. Further observations will thus be needed to conclude the effects of the two EPFs on the parasitism of S. frugiperda.…”

“…In Ghana, parasitism was reduced in some fields treated with emamectin benzoate [31]. Similarly, M. anisopliae ICIPE 7, M. anisopliae ICIPE 41 and M. anisopliae ICIPE 78 reduced the emergence of C. icipe and parasitism of S. frugiperda in Kenya [32,33]. This is an indication that although biopesticides are considered more ecofriendly, they may have detrimental effects on natural enemies.…”

Efficacy of Metarhizium anisopliae, Isolate ICIPE 7, against Anopheles arabiensis, Glossina fuscipes, and Rhipicephalus spp.

“…arabiensis mosquitoes and hence may be used in their control. ICIPE 7 has previously been shown to infect and kill species of ticks [ 44 ] and has more recently been confirmed to infect and kill fall armyworm larvae [ 51 ]. Our findings further illustrate the potential of this isolate in the management of multiple vectors of medical and veterinary importance.…”