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Techniques for Radiographing and the Accuracy of the X-Ray Method for Identifying and Estimating Numbers of the Mountain Pine Beetle1

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X.ray-exposure curves using 2 kilovoltages (kv) were developed for lodgepole pine slabs of different thickness and moisture content. X-ray exposure at 25 kv for a wood-and-bark slab containing 30% moisture varied, for example, from 4.5 milliampere minutes (mam) for a 1.5- inch-thick slab to 20 mam for a 3-inch-thick slab. The relationship between wood-and-bark thickness and optimum exposure became increasingly curvilinear as moisture content increased. In contrast, X-ray exposure at 45 kv for wood and bark containing 30% moisture varied from 0.4 mam for a 1.5-inch-thick slab to 1.25 mam for a 3- inch-thick slab. At 45 kv the relationship between wood-and- bark thickness and exposure remained approximately linear for all moisture contents.

Identifications and estimates of numbers of the mountain pine beetle, Dendroctonus ponderosae Hopkins, were obtained from radiographs. Radiographs obtained using an exposure of 25 kv proved to be best for identifying and determining numbers of small and medium-Sized larvae. Radiographs obtained using either 25 or 45 kv could be used with about equal accuracy for identifying and estimating numbers of large larvae, pupae, and cal- low adults. Errors in identification and in estimating numbers of beetles from radiographs obtained using an exposure of 25 kv were less than 10% of the mean and seem acceptable for population studies of bark beetles.

Document Type: Research Article

Publication date: June 1, 1969

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  • Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.
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