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Some effects of host tree nutrition on establishment and survival of the balsam woolly aphid, Adelges picease (Ratz) Carrow, Justin Roderick

Abstract

A greenhouse study was undertaken to investigate some relationships between nutrition of the host tree, Abies amabilis, as influenced by soil fertility and nitrogen fertilizers, and biology of the balsam woolly aphid, Adelges piceae (Ratz.). Seedlings were reared in two soil regimes - nutrient-deficient mineral soil and enriched humic soil. All trees were infested with aphid larvae, and observations made to determine the influence of soil fertility on the establishment rate of larvae on host trees. Subsequently, groups of 10 trees were treated with foliar nutrients, using ammonium nitrate and urea in various concentrations. The establishment rate of larvae on humic soil host trees was 2.5 times greater than on mineral soil trees. In addition, growth rate of the aphid population on humic soil trees was 37% greater than on mineral soil trees over a four week period. Soil fertility also influenced the life history of the insect. One foliar nutrient adversely affected the aphid population. Over a 10 week period, the aphid population on trees treated with 1% ammonium nitrate decreased by 23%, whereas the control population Increased 30.9%. It is postulated that this foliar treatment manifests its adverse effect primarily by inhibiting initial settling of larvae on the host trees. This inhibition may be related to fertilizer-induced alterations in the amino acid composition of feeding tissue.

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