1st Place: Natural enemy community responds to management in pecan orchards: Implications of hedging and pesticides

Perennial tree systems often require pruning programs to achieve productivity and/or to keep orchards amenable to management. In mature pecan orchards (Carya illinoinensis), where trees are tall and canopies start overlapping, hedge-pruning can mitigate shading effects and improve pesticide coverage within the canopy. However, canopy restructuring can also alter microclimatic parameters (e.g., temperature and relative humidity) and availability of plant resources (e.g., increasing young foliage due to regrowth or diminishing shelter as branches are removed) within the tree strata. The manner in which arthropod populations respond to these within-canopy habitat alterations is still unexplored. Hence, here we investigated the within tree abundance of natural enemy communities (predators and hymenopteran parasitoids) in response to hedge-pruning (hedged vs non-hedged trees) in the presence or absence of chemical pest management (i.e., fungicide and insecticide sprays). Sampling was performed by suctioning tree foliage for 30 seconds (with the aid of a reverse leaf blower) at three different heights of the pecan canopy (lower, middle and upper strata). We found a variety of parasitoids and predators (e.g. Orius spp, the most abundant natural enemy). Preliminary analysis suggests a higher abundance of both parasitoid wasps and predators in hedge-pruned trees regardless of chemical management treatments. While the predator community was found evenly distributed within the canopy strata, parasitoids were more abundant in the lower canopy. Overall, the higher abundance of natural enemies in hedge-pruned pecans reinforces the importance of acknowledging how habitat manipulation can modulate insect communities and raises questions about the mechanisms underlying such events.