Grapholita libertina Heinr. larvae are a pest of economic importance in lingonberries (partridgeberries), Vaccinium vitis-idaea L. var. minus Lodd, in Newfoundland. Both domestic and export markets are affected. Surveys conducted during the period 1973–1982 to determine distribution and larval population levels, in localities where berries were harvested commercially, indicated they were infested to varying intensities in all 15 localities studied. Highest infestations occurred at Pouch Cove (5 September 1974 — 122 larvae per kilogram of ripe berries) and on Witless Bay Line (9 August 1977 — 276 larvae per kilogram of green berries).
In experiments conducted from 1980 to 1982 at six locations, there was a significant decrease in level of infestation as the crop reached maturity. Our results suggest that delaying the opening of the lingonberry harvest season until the last week of September decreased the risk of infestation.
Observations on the life history of G. libertina and a naturally occurring hymenopterous parasite are presented.