ARS | Publication request: Oviposition Preference for Water-Stressed Plants in Orius Insidiosus (Hemiptera: Anthocoridae)

Submitted to: Journal of Insect Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 13, 2010
Publication Date: January 16, 2011
Citation: Seagraves, M.P., Riedell, W.E., Lundgren, J.G. 2011. Oviposition preference for water-stressed plants in Orius insidiosus (Hemiptera: Anthocoridae). Journal of Insect Behavior. 24:132-143.

Interpretive Summary: The insidiosus flower bug, Orius insidiosus, is an important predator of the invasive soybean aphid. This natural enemy lays its eggs into plant material and feeds on plants, in an unharmful way, to supplement its diet throughout life. This paper is a continuation of an effort to understand underlying factors leading to reproduction by important natural enemies of the soybean aphid. This information is important for designing cropping systems with increased ecosystem services from beneficial insects. This study was conducted to determine whether manipulating plant quality, via stress, within a single plant species (Phaseolus vulgaris L.) would impact the oviposition behavior of O. insidiosus and the subsequent performance of its offspring. Plants that had water withheld (water-stressed treatment) smaller than plants that were watered to alleviate the drought stress (unstressed treatment). In comparison to unstressed plants, water-stressed plants had less relative water content, greater sap osmotic potential and greater concentrations of amino-nitrogen. Orius insidiosus laid 70% more eggs per cm2 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. Studies such as these are important to informing more sustainable farming systems and how beneficial insects will respond to drought stress.

Technical Abstract: Plant species affects 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 impact 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 cm2 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.