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Research article2024Peer reviewedOpen access

Host-dependent larval migration and parasitism risk in a polyphagous moth

Martel, Veronique; Schlyter, Fredrik; Sadek, Medhat M.; Hegazi, Esmat M.; Glaus, Valentine; Hansson, Bill S.; Anderson, Peter

Abstract

Female herbivorous insects are expected to oviposit on the host plant providing the best performance of the offspring. However, in some insects the larvae are mobile and are not totally dependent on the mother's choice. They can change host plant when conditions for development or exposure to natural enemies vary between individual plants within a patch. Here we study larval migration and preference between two host plants, cotton and alfalfa, in the Egyptian leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). Previous studies have shown that although larval performance is better on cotton, females prefer to oviposit on alfalfa, and this preference corresponds to a higher survival of the eggs. In this study, S. littoralis larvae showed directed movement between host plants and were found to prefer alfalfa over cotton in field test in Egypt, as well as in laboratory selection of feeding site assays. To determine effects by natural enemies, the parasitism rates and various life-history traits were measured for one larval parasitoid, Microplitis rufiventris Kokujev (Hymenoptera: Braconidae), on several host plants including cotton and clover (equivalent host plant to alfalfa). Overall, parasitism was higher on cotton and parasitoid performance (cocoon mass, adult longevity, and female egg load) was better on cotton compared to clover. This fact suggests an enemy-free space on clover and alfalfa, as parasitism rate is higher on cotton, and the parasitoid performance is also better on cotton-fed larvae.Larval migration was investigated in the Egyptian leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae). Larvae showed directed movement between host plants and were found to prefer alfalfa over cotton in field and laboratory tests, even though larval performance is better on cotton. However, parasitism rates were higher and parasitoid performance (cocoon mass, adult longevity, and female egg load) was better for the larval parasitoid Microplitis rufiventris (Hymenoptera: Braconidae) on cotton, suggesting enemy-free space on alfalfa.image

Keywords

Braconidae; dispersal; enemy-free space; feeding; host plant choice; Hymenoptera; Lepidoptera; Microplitis rufiventris; Noctuidae; performance; preference; Spodoptera littoralis

Published in

Entomologia Experimentalis et Applicata
2024, Volume: 172, number: 6, pages: 523-532 Publisher: WILEY