Abstract
We tested the behavioral responses of ovipositing females and natal larvae of two sibling species, a generalist Helicoverpa armigera (Hübner) and a specialist Helicoverpa assulta (Guenée), to odor sources emitted from different combinations of six plant species (tobacco, Nicotiana tabacum; hot pepper, Capsicum annuum; tomato, Solanum esculentum; cotton, Gossypium hirsutum; peanut, Arachis hypogaea; maize, Zea mays). Under the conditions of plant materials versus corresponding controls, both stages of both species could find their corresponding host plants. However, H. assulta females and larvae exhibited a supersensitive and an insensitive response, respectively. Under the conditions of tobacco paired with each plant species, H. assulta females exhibited more specialized ovipositional response to tobacco than its sibling. When each plant species were combined with tobacco and tested against tobacco reference, peanut played an opposite role in the two species in their ovipositional responses to tobacco, and cotton can enhance the approaching response of H. armigera larvae when combined with tobacco. It seems that two attractive host plants also can act antagonistically with respect to host selection of the generalist via volatile exchange. Tomato should better be excluded from host list of H. assulta.
Highlights
Intercropping system design based on natural ecosystem mimicry has been becoming a hotpoint of sustainable pest management, which calls for in-depth knowledge about host selection process of phytophagous insects under a highly complex odorant background [1,2]
One or more stages mentioned above would be affected via volatile exchange between a host plant and its neighbors, irrespective of their health statuses ([5], and References therein)
H. assulta females could only recognize tomato as non-host plant, exhibiting a supersensitive response; instead, conspecific larvae could only detect their major hosts and could not actively avoid volatiles emitted from potential non-host plants, exhibiting an insensitive response (Fig 5, see in S2 Dataset)
Summary
Intercropping system design based on natural ecosystem mimicry has been becoming a hotpoint of sustainable pest management, which calls for in-depth knowledge about host selection process of phytophagous insects under a highly complex odorant background [1,2]. Field observation and laboratory bioassay, have often been used in the studies intended to interpret why fewer pests are found on host plants growing in more diverse backgrounds than on those in monoculture. While many laboratory bioassays using various solvent extracts or isolated compounds from plant parts as odor sources, rather than living. Helicoverpa select hosts in complex plant environments plants, provided poor insights into natural host selection by ovipositing females of phytophagous insects. Host selection of adult females follows a sequence of searching, orientation, encounter, landing, leaf surface evaluation, and host acceptance [4]. One or more stages mentioned above would be affected via volatile exchange between a host plant and its neighbors, irrespective of their health statuses ([5], and References therein)
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