INTRA-CROWN AND INTER-CROWN DISTRIBUTION OF THE EASTERN SPRUCE GALL ADELGID, ADELGES ABIETIS (L.), ON YOUNG WHITE SPRUCE

Intra- and inter-crown distribution of eastern spruce gall adelgid, Ad elges abietis (L.) (Homoptera: Adelgidae), on young white spruce, Pice a glauca (Moench) Voss., was studied at three sites in New Brunswick, Canada. Within a branch, the majority of galls were found on lateral s hoots. Similar distributions of galls within trees were observed regar dless of whether 20 or 30 lateral shoots or all shoots on a branch wer e sampled. Gall densities were highest on mid-crown branches of open-g rown trees 1-4 m tall and were not influenced by cardinal direction. A fter crown closure, most galls were found in the upper crown, above th e point of branch overlap. In all circumstances, gall distributions we re strongly clumped within trees. Inter-tree distribution of A. abieti s galls differed significantly from a Poisson but not a negative binom ial distribution, indicating a high degree of aggregation among trees. Therefore, a stratified random sampling plan using 20 lateral shoots of a mid-crown branch as a sampling unit would be adequate for monitor ing A. abietis populations. If the mid-crown branches are undergoing c rown closure, we suggest sampling in the lowest open-grown branch abov e the point of crown overlap.