Effects of aphicides on pecan aphids and their parasitoids in pecan orchards

Authors: SLUSHER, EDDIE - University Of Georgia; Cottrell, Ted; ACEBES-DORIA, ANGELITA - University Of Georgia

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2021
Publication Date: 3/12/2021
Citation: Slusher, E.K., Cottrell, T.E., Acebes-Doria, A.L. 2021. Effects of aphicides on pecan aphids and their parasitoids in pecan orchards. Insects. 12(3)241. https://doi.org/10.3390/insects12030241.
DOI: https://doi.org/10.3390/insects12030241

Interpretive Summary: Insecticide application is the primary method for aphid management in commercial pecan orchards in the U.S. However, over-reliance and non-judicious insecticide use has led to numerous downsides including insecticide resistance and impairment of beneficial insects. It is important to assess the efficacy and potential non-target impact of insecticides in order to create sustainable management programs. The objective of this study was to assess two grower standard products (flonicamid, sulfoxaflor, and a new product for pecans: afidopyropen) on pecan aphids and their parasitoid 7-, 14-, and 21-days-post application in 2019 and 2020. In 2019, non-treated trees had up to 9-fold more aphids than treated trees 7-days post application, but these differences diminished at 14 and 21 day assessments. In 2020, aphid numbers were low but non-treated trees had significantly more aphids in the lower canopy than most treated trees 7-days post application. These differences diminished for the later assessments. There was no significant difference in parasitoid adults or pupae between non-treated trees and treated trees. The results of this study indicate that growers have multiple products for aphid management thus allowing product rotation to decrease aphid resistance. Additionally, these products did not have negative impacts on parasitoids.

Technical Abstract: Aphids are an important pest of pecans in Georgia. Traditionally, insecticides have been the primary method of management. However, over-reliance and non-judicious use has led to resistance and damage to natural enemy populations. Therefore, frequent assessment of insecticides is necessary in order to monitor resistance development and non-target impacts. Aphicides, flonicamid, sulfoxaflor, afidopyropen were assessed for their effects on pecan aphids and parasitoid, Aphelinus perpallidus, in a mature pecan orchard using a randomized complete block design in 2019 and 2020. Post-application assessments were performed 7-, 14-, and 21-day-post application. Leaf samples from non-treated trees had greater aphid numbers than treated trees 7-days post application with differences diminishing throughout the other two treatment periods in 2019. In 2020, aphid numbers were lower but leaf samples from non-treated trees had more aphids than treated trees 7-days post application in the lower canopy. These differences again diminished 14- and 21-day-post application. There was no difference among treatments in number of parasitoid pupa and adults. These findings indicate that pecan growers have multiple potential options available for aphid management that do not negatively impact the primary pecan aphid parasitoid. Implications of the results on pecan aphid management are discussed.