. Infestation characteristics of the balsam woolly aphid in the Pacific Northwest. Fir Diseases and pests Northwest, Pacific; Adelges Northwest, Pacific. of limbs and where limbs join the main stem (fig. 9). Later, as the tree grows, the bark develops fis- sures, and the resin hardens. The cracks in the bark permit aphids to reinfest the areas previously aban- doned. Often, the first characteristic of crown decline is a drooping of the Figure areas from aphid terminal 10 to 15 feet of the crown (figs. infestation on the basal portion 10 and 11); eventually, often during the first 0
. Infestation characteristics of the balsam woolly aphid in the Pacific Northwest. Fir Diseases and pests Northwest, Pacific; Adelges Northwest, Pacific. of limbs and where limbs join the main stem (fig. 9). Later, as the tree grows, the bark develops fis- sures, and the resin hardens. The cracks in the bark permit aphids to reinfest the areas previously aban- doned. Often, the first characteristic of crown decline is a drooping of the Figure areas from aphid terminal 10 to 15 feet of the crown (figs. infestation on the basal portion 10 and 11); eventually, often during the first 0f grancj fjr limbs, winter, the top breaks off. Typically, the lower limbs become infested and develop distress symptoms before those in the upper crown; thus, infested grand fir often appears to be dying from the bottom upwards. Figure 10.—Top-curl from balsam woolly aphid infestation on grand Figure from infestation on subalpine fir. Down-crook at end of limbs is also Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Mitchell, R. G; Pacific Northwest Forest and Range Experiment Station (Portland, Or. ). [Portland, Or. ] : Pacific Northwest Forest and Range Experiment Station, Forest Service, U. S. Dept. of Agriculture
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