A deadly encounter: Alien invasive Spodoptera frugiperda in Africa and indigenous natural enemy, Cotesia icipe (Hymenoptera, Braconidae)

The invasion and wide spread of Spodoptera frugiperda represent real impediments to food security and the livelihood of the millions of maize and sorghum farming communities in the sub-Saharan and Sahel regions of Africa. Current management efforts for the pest are focused on the use of synthetic pesticides, which are often economically unviable and are extremely hazardous to the environment. The use of biological control offers a more economically and environmentally safer alternative. In this study, the performance of the recently described parasitoid, Cotesia icipe, against the pest was elucidated. We assessed the host stage acceptability by and suitability for C. icipe, as well as its ovigenic status. Furthermore, the habitat suitability for the parasitoid in the present and future climatic conditions was established using Maximum Entropy (MaxEnt) algorithm and the Genetic Algorithm for Rule-set Prediction (GARP). Cotesia icipe differentially accepted the immature stages of the pest. The female acceptance of 1(st) and 2(nd) instar larvae for oviposition was significantly higher with more than 60% parasitism. No oviposition on the egg, 5(th) and 6(th) larval instars, and pupal stages was observed. Percentage of cocoons formed, and the number of emerged wasps also varied among the larval stages. At initial parasitism, parasitoid progenies, time to cocoon formation and overall developmental time were significantly affected by the larval stage. Egg-load varied significantly with wasp age, with six-day-old wasps having the highest number of mature eggs. Ovigeny index of C. icipe was 0.53. Based on the models, there is collinearity in the ecological niche of the parasitoid and the pest under current and future climate scenarios. Eastern, Central and parts of coastal areas of western Africa are highly suitable for the establishment of the parasitoid. The geographic distribution of the parasitoid would remain similar under future climatic conditions. In light of the findings of this study, we discuss the prospects for augmentative and classical biological control of S. frugiperda with C. icipe in Africa.

Automated summary

The invasion and spread of Spodoptera frugiperda pose a significant threat to maize and sorghum farming communities in sub-Saharan Africa. Current efforts focused on synthetic pesticides are economically unviable and environmentally hazardous, making biological control using parasitoids like Cotesia icipe a more sustainable alternative. This study found that C. icipe preferentially targets younger larval stages of the pest and identified suitable habitats for its establishment in current and future climates.