Observations on the Distribution of the Spruce Bud Midge (Rhabdophagaswainei Felt) in Black and White Spruce Crowns and Its Effect on Height Growth

Abstract

Populations of the spruce bud midge (Rhabdophagaswainei Felt) were sampled on 1 to 6 ft tall black and white spruces (Piceamariana (Mill.) BSP. and P. glauca (Moench) Voss) in central Alberta. The incidence of attacked buds is described in relation to tree height and crown aspect, and in relation to terminal buds of the leader and top whorl branches. Some characteristics of the infested bud are given to assist in its recognition in the field.After leader terminal buds of young white spruce were removed to simulate midge damage, height loss during the same year averaged 25.3%. Normal height growth was resumed in the following year from an apical-dominant lateral branch. The study suggested that, for general surveys, a count of the number of attacked terminal leader buds in young spruce could provide a useful index of midge abundance and provide the basis for estimating its impact on tree height growth.