|Wyckhuys, K A|
Submitted to: Biocontrol
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/2008
Publication Date: 5/1/2008
Citation: Lundgren, J.G., K. Wyckhuys, N. Desneux. 2009. Population Responses by Orius insidiosus to Vegetational Diversity. BioControl. 54(1):135-142. Available online. Interpretive Summary: The current research examined the effects of vegetational diversity on the demographics of the omnivore Orius insidiosus, which is a habitat generalist frequently encountered in terrestrial systems of North America. In this work, we examined the egg, nymph, and adult abundance in monoculture soybean fields compared with fields diversified with non-crop plants. We found greater nymph and adult populations in the diverse plots, but egg densities were the same. Upon closer examinations, we found that O. insidiosus was laying a greater number of eggs on non-crop plants within the polycultures. Olfactometer assays were used to determine that naïve females did not distinguish among volatile plant odors. But when nymphs were reared on the different plant species in the laboratory, nymphal survival was correlated with female oviposition preferences. Thus, our research suggests that while vegetational diversity does not encourage more reproduction in field populations of O. insidiosus, the nutritional or architectural qualities of non-crop plants in diversified habitats led to higher fitness in developing nymphs. The implications of these results to the population dynamics of omnivorous insects and to biological control are discussed.
Technical Abstract: 1) Vegetational diversity is known to affect generalist predator populations, but the mechanisms that drive these natural enemy populations in vegetationally diverse systems are poorly understood. Here, we document how the demographics of an omnivorous bug, Orius insidiosus, respond to mono- and polycultures in the field, and investigate how host plant volatiles and relative plant quality may explain the observed patterns. 2) Vegetationally diverse (soybean and agronomic weeds) and monoculture (soybean only) treatments were established, and the abundance of different developmental stages of O. insidiosus and its most abundant arthropod prey were recorded. Orius insidiosus adults and nymphs were found at greater abundance in vegetationally diverse plots than in monocultures. A similar number of O. insidiosus eggs were found in the two treatments, but twice as many eggs were laid on non-crop plants than on soybeans within the vegetationally diverse plots. 3) In olfactometer assays, naive O. insidiosus females were unresponsive to odors from three weed species of varying acceptability to ovipositing females (morning glory, redroot pigweed and velvetleaf). 4) Under laboratory conditions, nymphs were reared on five species of agronomically relevant plants of varying suitability to ovipositing females. Nymphs survived significantly better on morning glory than on soybeans, suggesting that superior nymphal survival on non-crop plants may contribute to increased O. insidiosus populations in vegetationally diverse fields. 5) This research suggests that higher abundance of O. insidiosus in vegetationally diverse habitats could be related to improved fitness of the predator, which in turn is related to certain plant qualities (e.g., nutrition, plant architecture, etc.). Proximal cues are likely more influential to oviposition decisions by O. insidiosus females than volatile signals, and oviposition preferences were closely tied to the quality of different host plants for developing nymphs.