Techniques for Determining the Toxicity of Pine Resin Vapors to Dendroctonus brevicomis and D. jeffreyi

Several procedures were explored to obtain a suitable technique for determining the fumigant toxicity of pine resin vapors to adult bark beetles. The most suitable fumigation chamber used was a 150-cc. screw-cap jar with a teflon plastic gasket, though a cork-stoppered 30-cc. test tube had certain limited uses. Beetles were held within the chamber in individual cells of glass and lumite screening. Fresh resin, collected from trees by a mierotap device, was apportioned by volume, and the dosage of vapor in a chamber was determined by changes in weight of the resin sample. A saturated atmosphere of resin vapor was reached within 24 hours after placing a resin sample in the chamber. A 150-cc. volume was saturated by approximately 2 mg. of vapor of Pinus ponderosa Laws. resin, by 20 mg. of P. jeffreyi Grev. & Balf and by 6 mg. of P. jeffreyi ✕ ponderosa. Using Dendroctotnus brevicomis Lec. as the test insect, it was found that light, evaporative area of resin, and volume of the chamber did not alter the mortality rate of the beetle. Size and sex of the beetle, species of resin, and temperature of the chamber did alter the mortality rate.