Attracting Chrysopidae with plant volatiles for lace bug (Hemiptera: Tingidae) control in rhododendrons and azaleas

Authors: GRAHAM, KATERINA - Oregon State University; Choi, Man-Yeon; Lee, Jana

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2020
Publication Date: 9/1/2020
Citation: Graham, K.V., Choi, M.Y., Lee, J.C. 2020. Attracting Chrysopidae with plant volatiles for lace bug (Hemiptera: Tingidae) control in rhododendrons and azaleas. Journal of Insect Science. 20(5). https://doi.org/10.1093/jisesa/ieaa078.
DOI: https://doi.org/10.1093/jisesa/ieaa078

Interpretive Summary: The azalea lace bug is an invasive pest of rhododendrons and azaleas. This insect’s feeding activities causes yellow stippling on the upperside of leaves and, on the underside, a displeasing sticky residue. The infested plant’s ability to carry out photosynthesis is greatly diminished, and it will eventually die if the pest population is not reduced. Rhododendrons and azaleas are popular ornamental bushes and the nursery industry is the largest agricultural industry in the state of Oregon. Thus, the potential economic impact of the azalea lace bug is high unless measures are taken to control it. Whereas customers will not purchase plants that are less than perfect, they have more tolerance for damage when plants become infested if they are already part of a landscape. Because of this, an alternative control may be more feasible in such a setting. Our study asked if a naturally-occurring predator called a green lacewing could be attracted to azalea lace bug infested plants using synthetic compounds that mimic those naturally released by plants. Such compounds are a “help me” signal to predators which can track the scent(s) back to the plant under attack, simultaneously consuming the pest and relieving the plant from its attacker. Our results showed some compounds did attract the green lacewing, yet they did not result in a marked decrease in the number of azalea lace bug adults, nymphs or eggs laid. We also noted the effect on the populations of other common natural enemies; none of the compounds showed a consistent effect on any of the identified groups.

Technical Abstract: The azalea lace bug (Stephanitis pyrioides Scott) (Hemiptera: Tingidae) is an invasive pest of rhododendrons and azaleas (Ericaceae: Rhododendron) which feeds on the underside of leaves causing chlorosis, reduced photosynthesis and even plant death. While insecticides can control this pest, growers, landscape managers and homeowners have requested softer alternatives. Augmentative release of predatory green lacewing Chrysoperla (Neuroptera: Chrysopidae) eggs and larvae has reduced S. pyrioides, but large scale implementation may not be practical nor cost effective. Attracting naturally-occurring Chrysopidae with plant volatiles may be an economical and convenient option. In this study, we tested whether volatiles blends: 1) attracted Chrysoperla spp., and 2) controlled S. pyrioides populations on Rhododendron spp. in farm or urban landscapes. Experimental plots contained different multicomponent lures placed aboveground next to infested plants. Adult Chrysoperla, other natural enemies and S. pyrioides from egg to adult stages were monitored in both farm and urban landscapes for two summers. Overall, sticky traps near plants baited with methyl salicylate + acetic acid + 2-phenylethanol (methyl salicylate blend) or acetophenone + acetic acid + 2-phenylethanol (acetophenone blend) captured more adult Chrysoperla than control traps in farm landscapes; a blend of phenylacetaldehyde + methyl salicylate + acetic acid did not differ from the control. Only the acetophenone blend in a farm landscape was associated with a reduction of S. pyrioides. As a side objective, impacts on other natural enemies were evaluated; abundance of spiders, predatory hemipterans and Chalcidoidea differed by treatment.