Radiography in Forest Entomology1

The use of radiography in the study of cryptic insects was investigated for several kinds of forest insect damage. Longwave or “soft” X-rays (5-35 kilovolts) were found most suitable for the detection and study of insects infesting plant material. A portable industrial X-ray unit was used which had an output of up to 35 kilovolts, 10 milliamperes, and variable exposure time. Excellent results were achieved in radiographs of western pine beetle larvae and pupae in ponderosa pine bark; adult gallery construction and larval development of Ips confusus (LeConte) ; red turpentine beetle in situ in sugar pine; buprestids, cerambycids, siricids, and lyctids infesting various thicknesses and kinds of timber; weevils infesting lodgepole pine tips and seed-infesting insects. Less satisfactory was the detection of insects in whole cones, although their galleries could be detected.