Suppression of Gnathotrichussulcatus with sulcatol-baited traps in a commercial sawmill and notes on the occurrence of G. retusus and Trypodendronlineatum

Abstract

Sulcatol (6-methyl-5-hepten-2-ol), population aggregation pheromone for Gnathotrichus sulcatus (LeConte), was deployed in traps at three locations in a commercial sawmill at Chemainus, B.C., during 1975. Traps were baited full time in one location and for alternate biweekly periods in the other two. Unbaited traps were operated continuously in a control location. Freshly sawn lumber was set out at weekly intervals in each location and numbers of attacks on this and other lumber, as well as the number of beetles caught on traps, were monitored weekly. After a mill shutdown (July through October), the number of beetles captured steadily decreased, probably because of diminished input of beetles in field-attacked logs. Suppression ratios (number of beetles caught on traps: (number of estimated beetles in lumber + number caught on traps)) were highest (0.70 and 0.87 for male and female beetles, respectively) in the continuously baited location and indicated that sulcatol-baited traps have good potential in suppression of mill populations of G. sulcatus. Lumber was most severely attacked 2–4 weeks after sawmilling, suggesting development of and subsequent decrease in primary and secondary attraction. Significantly greater attack on lumber next to sulcatol-baited traps than on more distant lumber indicated that male beetles were attracted to the area of a trap but not necessarily to the point source of the pheromone. Mean percentage moisture of attacked boards was 62.3, while that of adjacent unattacked boards was 46.6. Boards attacked in July had a mean percentage moisture of 26.0 when sampled in September and no longer contained beetles. The first verified attacks of freshly sawn lumber by Trypodendron lineatum (Olivier) and G. retusus (LeConte) are recorded. Future control of G. sulcatus in sawmills may use sulcatol-baited traps, placed next to piles of attractive fresh slabbing which could be colonized by beetles not captured in the traps, and which subsequently could be removed and processed into pulp chips.