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.