Effectiveness of Thiodan, Sevin, and Lindane on Insects Attacking Freshly Cut Douglas-Fir Logs1

Bark of freshly cut Douglas-fir trees ( Pseudotsuga menziesii (Mirb.) Franco) in the forest was sprayed until runoff with 25% Thiodan® (6,7,8,9,10,10-hexachloro-1,5,5a, 6,9,9a-hexahydro-6,9- methano-2,4,3-benzodioxathiepin-3-oxide) and 25% lindane wettable powders and 50% Sevin®(1-naphthyl N-methyl carbamate) wettable powder, each in dilutions of 1 pound and 3 pounds active ingredient to 100 gallons of water. Lindane was the referent insecticide. All insecticide applications completely protected against insect attack for at least 8 weeks after application except Sevin at 1 pound active ingredient. After 19 weeks no successful attacks of the Douglas-fir beetle ( Dendroctonus pseudotsugae Hopkins) had occurred on the bark treated with lindane at 3 pounds, or on either of the Thiodan treatments. Sevin at 3 pounds had 0.1 attack per square foot. Lindane at 1 pound had 0.2 attack per square foot. Sevin at 1 pound had 0.4 attack per square foot. Other bark and wood boring insects were proportionately fewer. On the untreated logs there were 2.3 attacks per square foot and they were much more extensive than on the treated logs. In this summary, abortive attacks are ignored. Sap stain and decay fungi were also retarded on treated areas. Termites were absent, although they were present on the untreated logs.