Identification, Microhabitat, and Ecological Niche Prediction of Two Promising Native Parasitoids of Tuta absoluta in Kenya

Simple Summary Since the arrival of Tuta absoluta, a multivoltine insect species whose larvae develop in leaves, fruits, flowers, buds, and stems of tomatoes, producers are facing one of its biggest production challenges. The pest continues to invade new areas, causing heavy losses in the tomato value chain. Sprays of synthetic insecticides have shown very low efficacy on this pest because of its inclination to develop resistance to various insecticide-active ingredients. Biological control is one of the most promising solutions for the management of this pest. In this work, we investigated the most efficient indigenous parasitoids associated with T. absoluta in Kenya and their preferable habitat and ecological niche suitability. We identified two species, Stenomesius sp. near japonicus and Bracon nigricans, with up to 17% and 21% parasitism respectively. Stenomesius sp. near japonicus was more abundant in greenhouses and non-insecticide-treated tomatoes while B. nigricans was more abundant in the field tomatoes with a low abundance of Nesidiocoris tenuis. The ecological niche of these two species showed that B. nigricans was suitable for establishment in sub-Saharan Africa, a big part of South America, and Australia in both current and future scenarios. Associations between the South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), and its native parasitoids need to be updated to increase the implementation of pest control strategies. In this study, T. absoluta-infested tomato plants were collected from three regions in Kenya. The emerged parasitoids were identified, and their abundance was correlated with agroecological parameters, viz. cropping systems, and the abundance of the predator Nesidiocoris tenuis Reuter (Hemiptera: Miridae). The study further conducted a habitat suitability prediction for the identified parasitoids. Two parasitoid species, Bracon nigricans (Szepligeti) (Hymenoptera: Braconidae) and Stenomesius sp. near japonicus (Ashmead) (Hymenoptera: Eulophidae) emerged from T. absoluta immature stages, with parasitism rates ranging from 0 to 21% and 0 to 17% respectively. Insecticide application and open field cropping negatively influenced the parasitism by S. sp. nr japonicus. Low occurrence of N. tenuis positively affected B. nigricans parasitism. The predicted occurrence of parasitoid species indicated vast suitable areas for B. nigricans in sub-Saharan Africa, Australia, and South America. Low suitability was observed for S. sp. nr japonicus in Africa. Therefore, native parasitoids, especially B. nigricans could be considered for implementation as a biocontrol agent in the Integrated Pest Management program of T. absoluta.

Automated summary

This study investigated the most efficient indigenous parasitoids associated with Tuta absoluta in Kenya and their ecological niche suitability. Two parasitoid species, Bracon nigricans and Stenomesius sp. near japonicus, were identified with differences in abundance and ecological niche. Bracon nigricans was considered suitable for biocontrol of T. absoluta.