Molecular analysis reveals lowbush blueberry pest predation rates depend on ground beetle (Coleoptera: Carabidae) species and pest density

Molecular gut-content analysis allows determination of pest predation by field-collected predators. Ground beetles (Coleoptera: Carabidae) common in lowbush blueberries may consume blueberry spanworm, Itame argillacearia (Packard) (Lepidoptera: Geometridae), and blueberry flea beetle, Altica sylvia Malloch (Coleoptera: Chrysomelidae), providing pest suppression. Using newly developed pest specific primers, laboratory feeding trials showed that the median detection time (MDT) for blueberry spanworm in the largest beetle, Carabus nemoralis O.F. Müller, was 3.7 h, whereas Poecilus lucublandus (Say) and Pterostichus mutus (Say) had MDTs between 27.1 and 31.6 h for both pests. At a field-site with high pest abundances, the probability of detecting blueberry spanworm and blueberry flea beetle DNA was greater in P. lucublandus, 26 and 39 % respectively, than in P.mutus, 8 and 20 % respectively. Only 0 and 1 % of P. lucublandus and P. mutus, respectively, tested positive for blueberry spanworm DNA at a second site with low abundance. At the first site, the probability of detecting pest DNA in both ground beetle species was positively related to pest density. Higher pest DNA detection rates and captures of ground beetles corresponded to field areas where significant pest reductions occurred from late May to early June. Conservation of predatory carabid beetles could lead to valuable biological control in lowbush blueberries.