The Biology, Damage and Within-Tree Distribution of the Spruce Bud Midge, Rhabdophaga swainei Felt (Diptera - Cecidomyiidae), on Black Spruce in Newfoundland : Insects Affecting Reforestation. Biology and Damage

1989

S. 213-223

1 Abb., 3 Tab., 13 Lit. Ang.

Unselbständiges Werk

200069390

Rhabdophaga swainei has one generation y year on black spruce in Newfoundland. Newly hatched larvae enter bud primordia of flushing shoots in late June and early July and larvae mature by fall to overwinter within buds. Pupation occurs within buds the following spring and adults emerge in June. The number of eggs dissected from virgin females averaged 86. Platygaster rhabdophagae MacGown (Platygastridae). Mesopolobus sp. (Pteromalidae), Torymus sp. (Torymidae) and Tetrasticus sp. (Eulophidae) were responsible for high parasitism levels. Terminal buds were attacked significantly more than lateral or uppermost lateral buds, and more infested buds were in the top third of the crown than at lower crown levels, but displayed no directional pattern according to crown aspect. An apical meristem never developed in infested buds which never flushed. The R. swainei larva redirects the growth of bud primordial cells to produce gall tissues that provide nutrients and an overwintering shelter. If a terminal leader bud is attacked, a subordinate bud assumes dominance and becomes the new leader shoot. During this transition there is a slight loss in height growth. Normal leader growth resumes the following year.