Non-target impacts of rotational hog grazing in Michigan apple orchards

Rotationally grazing hogs in tree fruit orchards has been found to provide partial management of plum curculio Conotrachelus nenuphar (Herbst), codling moth Cydia pomonella, and Oriental fruit moth, Grapholita molesta (Busck). These species spend part of their life cycle in the soil and in dropped fruit, both of which are disturbed by hogs. In this study, we investigated whether or not hogs impact non-target insects, earthworms, and other ground dwelling species. The experiment consisted of three control plots and three grazed plots of 2 acres each that were randomly selected and established in a Michigan apple orchard. In grazed plots, twenty-four Berkshire hogs were rotationally grazed during June and July of 2012 for two weeks. There were 12 replicates per plot. At each replicate point we sampled arthropods using pitfall traps and sticky cards. Earthworms were sampled by hand sorting and applying a hot mustard vermifuge. We sampled once before hogs entered plots and several times after hogs were grazed. All organisms were taken back to the lab, preserved, quantified, and identified at least to the family level.