Green lacewings and water sprays for azalea lace bug control

Authors: Lee, Jana; FINLEY, BARRY - Chemeketa Community College; FLORES, S. MICHAEL - Oregon State University; GRAHAM, KATERINA - Oregon State University; WOLTZ, J. MEGAN - Lindenwood University; WONG, JESSICA - Oregon State University; ROSETTA, ROBIN - Oregon State University

Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/2018
Publication Date: 12/1/2018
Citation: Lee, J.C., Finley, B., Flores, S., Graham, K.V., Woltz, J., Wong, J.S., Rosetta, R. 2018. Green lacewings and water sprays for azalea lace bug control. Journal of Environmental Horticulture. 36(4):119-125.

Interpretive Summary: The azalea lace bug is a serious pest of azaleas and rhododendrons which is often controlled by insecticides. However, softer approaches such as biological control and water sprays against this pest on rhododendrons is unknown. Therefore, we tested releasing the commercially available green lacewing predator, and water sprays on lace bug infestation in one laboratory and four field trials. First, 2nd instar predator larvae consumed lace bug nymphs and less frequently consumed adult lace bugs. Second, tapping predator larvae from its container over dry rhododendron leaves, and shaking loose eggs over wet leaves were reliable application methods. Third, predator larvae released onto potted rhododendrons lowered pest counts for two weeks. Fourth, after four bi-weekly applications on large landscape rhododendrons, plants receiving egg cards or water-sprays had reduced lace bug counts and fewer damaged leaves than control plants. Fifth, landscape plants receiving a water spray followed by predator egg releases had fewer pests and fewer damaged leaves than control plants. After pests were initially sprayed off, hatching predators might have consumed pests that hatched from eggs embedded in leaves.

Technical Abstract: The azalea lace bug, Stephanitis pyrioides, is a serious pest of azaleas and rhododendrons which is often controlled by systemic insecticides. However, the efficacy of softer approaches such as biological control and water sprays against this pest on rhododendrons is unknown. Therefore, we tested the commercially available green lacewing predator, Chrysoperla rufilabris, and water sprays on lace bug infestation in one laboratory and four field trials. First, 2nd instar predator larvae were confirmed to consume lace bug nymphs and sometimes adults. Second, tapping predator larvae from hexcel units over dry leaves of potted rhododendrons, and shaking loose eggs over wet leaves were reliable application methods. Third, predator larvae released onto potted rhododendrons lowered pest counts for two weeks. Fourth, after four bi-weekly applications on large landscape rhododendrons, plants receiving egg cards or water-sprays had reduced lace bug counts and fewer damaged leaves than control plants. Fifth, landscape plants receiving the sequential combination of water spray followed by predator egg releases had 44-90% lower pest abundance and fewer damaged leaves than the control. After pests were initially dislodged, hatching predators might have consumed hatching pests.