GROUND BEETLES (CARABIDAE) ARE AFFECTED BY MULCH IN ORGANIC HIGHBUSH BLUEBERRIES

Ground beetles (Carabidae) are important in agroecosystems because they may regulate pest populations. Carabids have been investigated in horticultural crops, but there are few studies in highbush blueberries. Mulching is used in highbush blueberries for weed control, moisture retention, and fertilization, but its impact on ground beetles is largely unknown. We evaluated the effect of pine needles, composted papermill biosolids, and composted manure/sawdust on carabids captured in pitfall traps from mid July to late September for three consecutive years. Captures of all carabids and the dominant species, Pterostichus melanarius (Illiger) increased in 2008 following mulch application in 2007. In both years, significantly more carabids were captured in compost manure/sawdust than pine needles. In 2009, captures in early September show significantly fewer total carabids and P. melanarius in pine needles compared to composted mulches and more P. melanarius in manure/sawdust mulch compared to soil. Harpalus rufipes (DeGeer) and Harpalus pensylvanicus (DeGeer) were captured more frequently in soil and manure/sawdust mulch compared to pine needles. Overall, carabids seem to avoid pine needles and may prefer composted mulches to soil. Preference is likely determined by abundance and quality of food sources in mulches. Potential of carabids, particularly the dominant species, to regulate blueberry maggot (Rhagoletis mendax Curran) is discussed.