The Larch Gall Midge in Seed Orchards of South Siberia

1988

S. 30-44

7 Abb., 3 Tab., 43 Lit. Ang.

Unselbständiges Werk

0-306-42745-1

200069187

The major factor affecting the populational dynamics of larch gall midges is polymorphism in larch bud development with respect to its synchrony with midge emergence and oviposition. This insect has little impact on the survival of its host plant, does not disperse far from its birthplace, and is not strongly affected by natural enemies. Thus, D. laricis belong to that group of forest insects that exhibit prodromal16 or gradient6,7 outbreaks. Sustained gradient outbreaks occur on larch trees or stands bearing predominantly type III buds (those that attain maximum needle growth at the time midge larvae are hatching). The infestation of trees with slow needle growth (type II) or late flushing buds (type IV), however, depends on spring temperatures so that gall midge populations may fluctuate unpredictably, exhibiting pulse gradient outbreaks.