Impact of the exotic fall armyworm on larval parasitoids associated with the lepidopteran maize stemborers in Kenya
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Impact of the exotic fall armyworm on larval parasitoids associated with the lepidopteran maize stemborers in Kenya Bonoukpoe` Mawuko Sokame . Julius Obonyo . Enock Mwangangi Sammy . Samira A. Mohamed . Sevgan Subramania . Dora Chao Kilalo . Gerald Juma . Paul-Andre´ Calatayud
Received: 11 August 2020 / Accepted: 12 October 2020 International Organization for Biological Control (IOBC) 2020
Abstract Exotic invasive insect herbivores have the potential to interfere with existing herbivore-natural enemy interactions in new environments. Fall armyworm (FAW), Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), is a new invasive pest in maize fields in Africa. Understanding the acceptability and suitability of FAW to existing maize stemborerparasitoid interactions is the first step in elucidating the impact that this exotic insect pest can have on the existing natural enemies used in biological control of maize stemborers in Kenya. The most commonly used
Handling Editor: Stefano Colazza B. M. Sokame (&) J. Obonyo E. M. Sammy S. A. Mohamed S. Subramania P.-A. Calatayud International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772-00100, Nairobi, Kenya e-mail: [email protected]; [email protected] B. M. Sokame D. C. Kilalo Department of Plant Science and Crop Protection, University of Nairobi, Kangemi, P.O. Box, 29053, Nairobi 00625, Kenya G. Juma Department of Biochemistry, University of Nairobi, P.O. Box 30197, Nairobi 00100, Kenya P.-A. Calatayud CNRS, IRD, UMR E´volution, Ge´nomes, Comportement et E´cologie, Universite´ Paris-Saclay, 91198 Gif-sur-Yvette, France
larval parasitoids for biological control programs against maize stemborer communities in East Africa are Cotesia flavipes Cameron (Hymenoptera: Braconidae) and two populations of the native Cotesia sesamiae (Cs-Inland and Cs-Coast) Cameron (Hymenoptera: Braconidae). All these parasitoid species attacked FAW larvae but none yielded offspring, although they induced high non-reproductive host mortality when compared to natural mortality. Furthermore, the parasitoids that inserted their ovipositor into FAW larvae exhibited no significant preference between FAW larvae and their respective stemborer hosts under dual-choice bioassays. In olfactometer bioassays, the parasitoids were more attracted to plants infested by FAW than uninfested plants and even showed a marked preference for the odours of plants infested by FAW over those of plants infested by their natural host counterparts. This study illustrates that exotic pests, such as FAW, can impact existing stemborer-parasitoid interactions associated with maize, even if they cannot be used as hosts by parasitoids associated with these stemborers. Although additional studies are needed, FAW might therefore have a negative impact on stemborer biological control existing before its invasion. Keywords Busseola fusca Chilo partellus Sesamia calamistis Sesamia nonagrioides Biological control Cotesia flavipes Cotesia sesamia
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