PRIMARY ATTRACTION OF IPS LATIDENS (LECONTE) AND HYLASTES GRACILIS LECONTE (COLEOPTERA: SCOLYTIDAE) TO HIGH-GIRDLED LODGEPOLE PINE, PINUS CONTORTA VAR. LATIFOLIA ENGELMANN

In the absence of secondary attraction, 2 species of Scolytidae, Ips latidens (LeConte) and Hylastes gracilis LeConte, showed significant preference while in flight for high-girdled over non-girdled lodgepole pines, Pinus contorta var. latifolia Engelmann. In contrast, beetles in 2 genera of Elateridae, Ampedus and Ctenicera, showed significant preference for non-girdled over high-girdled lodgepole pines. Beetles in 12 other families, as well as other scolytids and elaterids, did not show any significant preference or aversion to high-girdled trees. This is the first clear demonstration of primary attraction for a North American Ips species and the second for an Hylastes species.

SECONDARY ATTRACTION IN THE WESTERN BALSAM BARK BEETLE, DRYOCOETES CONFUSUS (COLEOPTERA: SCOLYTIDAE)

Evidence for secondary attraction in the western balsam bark beetle, Dryocoetes confusus Swaine, was obtained in laboratory bioassays and field experiments. Both sexes showed positive responses to volatiles of the host tree, Abies lasiocarpa (Hook.) Nutt., indicating that primary attraction is probably important in host selection by this species. Male beetles initiated attack and within 6 h produced an aggregation pheromone(s), which was present in frass and in pentane extracts of the abdomens of males excised from logs. Both sexes responded to the pheromone. Abdominal extract of unmated males which had bored into host bark for 14 days was still attractive. Pheromone production was induced by exposing males to host resin volatiles. Mating had no effect on male attractiveness, but induced females to produce an antiaggregation pheromone which, in laboratory bioassays, at least partially inhibited response to male attractant. The attractive volatiles from male-infested logs were successfully captured on Porapak Q®. The development of laboratory bioassay and pheromone extraction techniques indicates that a pheromone isolation program is feasible.

EFFECT OF THE LIVING HOST TREE (PICEA) ON THE RESPONSE OF DENDROCTONUS RUFIPENNIS (COLEOPTERA: SCOLYTIDAE) AND A PREDATOR THANASIMUS UNDATULUS (COLEOPTERA: CLERIDAE) TO FRONTALIN AND SEUDENOL

Two synthetic pheromones, frontalin and seudenol, were tested on living host (Picea) trees and on non-host (Abies) trees to determine their relative attractiveness to the spruce beetle (Dendroctonus rufipennis) and a clerid predator (Thanasimus undatulus). On host trees, frontalin attracted significantly more spruce beetles and induced significantly more attacks on the trees than did seudenol. On non-host trees, more beetles and a higher male ratio were attracted to seudenol than to frontalin. Frontalin has a positive effect on the behavior of female spruce-beetle attack, whereas seudenol has not. The resulting natural secondary attraction of attacking female beetles creates strong aggregation of both sexes of spruce beetles on host trees (Picea) baited with frontalin, but not on host trees baited with seudenol or on non-host trees (Abies). The clerid predator (T. undatulus) was attracted to frontalin in significatnly larger numbers than to seudenol.

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

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.

THE EFFECT OF MALE TRYPODENDRON LINEATUM (COLEOPTERA: SCOLYTIDAE) ON THE RESPONSE OF FIELD POPULATIONS TO SECONDARY ATTRACTION

The strong attractiveness of logs infested with female ambrosia beetles, Trypodendron lineatum (Oliv.), to the flying population was sharply reduced after the addition of males. The field response of T. lineatum was greatly reduced when air from logs infested with attractive females was mixed with air passing over logs infested with both sexes. The findings suggest that females keep producing the attracting principle in the presence of males. Males appear to reduce secondary attraction by producing a volatile substance(s) which may be anti-aggregating or repellent in its effect.