Population Densities of Lepidopteran Pests in Selected Cranberry Cultivars in Wisconsin

Host plant resistance, an important strategy of integrated pest management, was examined in the American cranberry, Vaccinium macrocarpon Aiton (Ericaceae). Despite the pressure on cranberry growers to reduce pesticide usage, host plant resistance is not used to help manage insect populations. This study measured field population densities of the three most economically important pest insects in Wisconsin, namely, cranberry fruitworm (Acrobasis vaccinii Riley), sparganothis fruitworm (Sparganothis sulfureana Clemens), and blackheaded fireworm (Rhopobota naevana Hübner), in five different cranberry cultivars, i.e., 'Stevens', 'Ben Lear', 'GH1', 'Mullica Queen', and 'HyRed'. Population densities of male moths of all three species were assessed using pheromone traps in beds of the different cranberry cultivars in commercial marshes in central Wisconsin. For each cultivar, damaged cranberries were collected, and the number of damaged berries and the number of larvae feeding within berries were compared among cultivars. More than 99% of larvae collected were cranberry fruitworm. Mullica Queen and Ben Lear had more damaged berries than Stevens or GH1, and had more larvae than GH1. Conversely, fewer adult male sparganothis fruitworm were found in Ben Lear and Mullica Queen beds than in beds of Stevens or GH1. Adult populations of cranberry fruitworm and blackheaded fireworm were not different among cultivars. Our findings provide evidence of different levels of resistance in common cranberry cultivars, which should inform future plantings and breeding programs.