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Aphids and associated parasitoids exhibit vertical canopy distribution differences in pecans


In agricultural systems, aphids (Hemiptera: Aphididae) have been shown to exhibit differences in within plant vertical distribution in vegetation. In addition, natural enemies, such as parasitoids, may have canopy micro-climate preferences. Currently, the within plant vertical distribution of aphids is primarily documented in row crops with few studies in tree systems. Pecan orchards under commercial production range from new to old with variable tree height between these orchards. This height difference highlights the need to examine the vertical canopy distribution of pecan aphids in trees of varying height. In this study, we evaluated the vertical canopy distribution patterns of aphids, parasitized aphids (i.e., mummies), and the primary parasitoid Aphelinus perpallidus (Gahan) (Hymenoptera: Aphelinidae) in pecan trees (Fagales: Juglandaceae) within younger (~ 9 m) and older trees (~ 15 m). Pecan aphids and mummies were often more abundant in the lower canopy, especially in older trees. Conversely, parasitoid adults were observed at higher abundance in the upper canopy of younger trees in 2021 and in both the lower and upper half of older trees, but there was variability in parasitoid distributions between years. Results indicate that scouting the lower canopy for aphids may be sufficient to estimate populations. The presence of A. perpallidus in the upper canopy can be beneficial as it may allow for biological control in areas where insecticide application may fail.

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The authors would like to thank the technical assistance of Pamela Halliday (UGA-Tifton), Kate Phillips (UGA-Tifton), Pedro Toledo (UGA-Tifton), Kirsten Flinn (UGA), Merry Bacon (USDA), Rebekah Hartley (USDA), and Quentin Read (USDA). This research was funded by Southern Sustainable Agriculture Research and Education (SARE) grant GS19-197, the Georgia Pecan Commodity Commission and Hatch Funds.

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Correspondence to Eddie K. Slusher.

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The authors declare no conflict of interest. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture. The US Department of Agriculture prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual's income is derived from any public assistance program.

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Slusher, E.K., Acebes-Doria, A.L., Cottrell, T. et al. Aphids and associated parasitoids exhibit vertical canopy distribution differences in pecans. BioControl 67, 563–570 (2022).

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  • Aphid-parasitoid interactions
  • Yellow pecan aphid
  • Blackmargined aphid
  • Black pecan aphid
  • Aphididae
  • Hemiptera