Oviposition Preference for Water-Stressed Plants in Orius insidiosus (Hemiptera: Anthocoridae)

Plant species affect the oviposition behavior of the zoophytophagous predator Orius insidiosus. This study was conducted to determine whether manipulating plant quality, via stress, within a single plant species (Phaseolus vulgaris L.) would affect the oviposition behavior of O. insidiosus and the subsequent performance of its offspring. Plants that had water withheld (water-stressed treatment) had about 20% less total dry weight than plants that were watered to alleviate the drought stress (unstressed treatment). In comparison to unstressed plants, unifoliolate leaves and petioles of water-stressed plants had about 20 and 12% less relative water content, 54 and 29% greater sap osmotic potential, and 19 and 70% greater concentrations of amino-nitrogen, respectively. Reproductive O. insidiosus were then presented stressed and unstressed plants in a two choice test to determine oviposition preference. First instar survival on the two treatments was evaluated in no-choice tests. Orius insidiosus laid 70% more eggs per cm(2) on the stressed plants. The lifespan of newly-hatched nymphs was the same in both treatments. Eggs were more frequently laid on the leaf vein than the petiole of unstressed plants, whereas in stressed plants oviposition on these parts occurred at equal frequency. These findings suggest that physiological changes in water-stressed bean plants created conditions more favorable for O. insidiosus oviposition. As there was no increase in offspring performance, it is hypothesized that females chose oviposition sites near preferred feeding sites or plant tissues that were less prone to desiccation.