The biology of the Birch Leaf Miner, Fenusa pusilla (Lepeletier) (Hymenoptera: Tenthredinidae) in Newfoundland

Jones, John Malcolm (1974) The biology of the Birch Leaf Miner, Fenusa pusilla (Lepeletier) (Hymenoptera: Tenthredinidae) in Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Birch Leaf Miner, Fenusa pusilla (Lepeletier), has been a pest of birch trees in North America since its introduction from Europe in the early 1920's. It was first reported in Newfoundland during 1959 on White Birch, Betula papyrifera Marsh. Since then damage by the leaf miner has been noted annually in the Province, particularly on roadside trees. -- This study was initiated in 1972 to determine the number of generations of F. pusilla per year in Newfoundland, the number of larval instars per generation, and the distribution of the insect in birch according to crown position and leaf age. -- In 1972 there were two complete generations and some individuals completed a third generation to the prepupal state. There were five larval instars in each generation. All birch leaves were vulnerable to infestation in the first generation, whereas in later generations eggs and larvae were more abundant on young leaves of terminal shoots. Larval mortality was substantial. It decreased from the first to third generation in White Birch whereas in Mountain White Birch, Betula cordifolia (Reg.) Fern., larval mortality was extremely high throughout the season. Five larvae were capable of totally destroying the photosynthetic tissue of leaves up to 60mm. long. -- Two parasitoid species of F. pusilla in Europe, Grypocentrus albipes (Ruthe) and Lathrolestes nigricollis (Thoms.) (both Hymenoptera: Ichneumonidae) were released onto Fenusa-infested birch in August 1972. Individuals of both species were recaptured in 1973.

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