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Title: Spray penetration and natural enemy survival in dense and sparse plant canopies treated with Carbaryl: implications for conventional and biological control

Author
item YEARY, WHITNEY - University Of Tennessee
item FULCHER, AMY - University Of Tennessee
item Zhu, Heping
item KLINGEMAN, WILLIAM - University Of Tennessee
item GRANT, JEROME - University Of Tennessee

Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2018
Publication Date: 5/19/2018
Citation: Yeary, W., Fulcher, A., Zhu, H., Klingeman, W., Grant, J. 2018. Spray penetration and natural enemy survival in dense and sparse plant canopies treated with Carbaryl: implications for conventional and biological control. Journal of Environmental Horticulture. 36(1): 21-29.

Interpretive Summary: Growers are subject to market pressure to produce plants with dense canopies. Canopy density may affect the efficacy of contact insecticides and the ability to use insecticides and natural enemies simultaneously. Insecticide applications are generally considered more effective on plants with a sparse canopy. In this study, spray penetration in dense and sparse canopies of select woody ornamental crops was characterized to determine if denser canopies could protect natural enemies from a foliar-applied contact insecticide. The canopy interior provided a safe place to release natural enemies as part of an augmentative biological control program. The use of natural enemies might be critical to controlling pests, such as scales, that infest the trunk and other interior positions of dense plant canopies, where spray coverage was minimal and in regions or markets implementing insecticide restrictions for pollinator protection. Tests also revealed spray coverage within the canopy interior was low regardless of canopy density, indicating that the interior of a plant could serve as a refugium for pest insects but also naturally occurring biological control organisms during an insecticide application.

Technical Abstract: Ornamental plant producers often rely on chemical control to manage insect pests. However, cultural practices, such as pruning, can influence plant architecture which may, in turn, affect pesticide penetration. Spray penetration was studied to determine the effect of canopy density on beneficial insect survival following insecticide application and to better understand the implications of canopy density on pest management. Regardless of canopy density or plant species, the interior position of the canopy received less than 8% spray coverage. The middle position of sparse canopies received 288 to 513% more coverage than the middle position of dense canopies. The middle and interior position of dense canopies protected greater than 50% of the convergent lady beetle (Hippodamia convergens (Gu´erin-M´eneville) population while only the interior position of dense canopies protected greater than 50% of green lacewing (Chrysoperla rufilabris Burmeister) populations.