Thumbnail Image

Interactions between a Gall Making Fly, Dasineura Oxycoccana (Diptera: Cecidomyiidae), And Its Host Plant, Cultivated Cranberry (Vaccinium Macrocarpon)

Cranberry tipworm, Dasineura oxycoccana Johnson (a gall‐making fly), disrupts normal growth of cranberry (Vaccinium macrocarpon Aiton) by injuring the apical meristem of shoots or uprights. The impact of larval feeding injury on reproductive parameters of cranberry was determined, from one growing season to next, at upright (Maine and Massachusetts, 2008 ‐ 2009) and plot levels (Massachusetts, 2009 – 2010 and 2010 ‐ 2011). I also estimated the proportions of uprights injured because of tipworm feeding at several cranberry production sites (Massachusetts and Maine) and the proportions of uprights that produced flowers and fruits in the next growing season. Tipworm‐injured uprights tagged at the end of the growing season did not produce floral‐units (following year) across sites in both Massachusetts and Maine. There was significant variation among the sampled sites in the proportions of tipworm‐injured uprights and also in the proportions of uprights with flowers in the next growing season (Massachusetts and Maine). A trend was apparent wherein sites with higher tipworm injury levels had relatively lower flowering proportions in the next growing season. However, sites in Massachusetts did not differ in the proportions of uprights that set fruit and in a replicated study, significant reduction in tipworm injury at plot level (using insecticide) did not impact flower and fruit production in the next growing season. A two‐year field study was carried out at three different locations to determine the impact of tipworm feeding injury on the reproductive and vegetative growth of two cranberry cultivars (‘Howes’ and ‘Stevens’) in Massachusetts. Individual uprights of cranberry exhibited tolerance to natural (tipworm) and simulated apical meristem injury in the current growing season (fruit production) and results were corroborated by a greenhouse study. In the field study, weight of fruit was higher intipworm‐injured uprights as compared with intact control uprights at the sites with Howes. However, majority of injured uprights (tipworm and simulated) did not produce new growth from lateral buds (side‐shoots) before the onset of dormancy. In the next growing season, fewer injured uprights resumed growth and produced flowers as compared with intact uprights at two of the three sites.