EFFICACY OF ANTIAGGREGANTS FOR THE PINE ENGRAVER, IPS PINI (COLEOPTERA, SCOLYTIDAE)

The responses of pine engravers, Ips pini (Say), in British Columbia t o ipsdienol-baited traps containing low medium, and high dose rates of the antiaggregants verbenone and ipsenol, released from impregnated p olyethylene and polypropylene beads, respectively, remained significan tly lower than responses to ipsdienol-baited control traps throughout the spring. During the summer, the responses remained low only in trap s containing medium and high dose rates of impregnated beads. Antiaggr egant treatment densities of 100 and 400 bubble cap release points per hectare reduced the numbers of pine engravers caught in ipsdienol-bai ted, multiple-funnel traps by 66.1 and 76.8%, respectively. In 50 X 50 m thinning-simulation plots treated with a broadcast distribution of antiaggregant-impregnated beads in 1990, 32.9% of the felled lodgepole pines, Pinus contorta Dougl., were attacked; in untreated control plo ts, 53.1% were attacked. The mean attack density per square metre of a vailable bark surface in the treated plots (1.3) was significantly low er than that in the untreated plots (1.9); however, where attack occur red there was no difference (8.8 and 9.4 attacks/m(2), respectively). In a 1991 experiment, verbenone- and ipsenol-impregnated beads were ap plied to 15 X 15 m thinning-simulation plots at initial release rates of 2.5 mg of verbenone and 0.05 mg of ipsenol per square metre of grou nd surface per day, and at double these rates. For three treatments, l ow and high rates 3 weeks prior to the first attack by I. pini and a h igh rate 2 weeks prior to attack, the mean attacks per square metre of available bark surface per week were reduced by 77.1, 82.9, and 97.1% , respectively, compared with attacks on felled pines in untreated con trol plots. The results of these experiments suggest that a timely app lication of broadcast antiaggregants would prevent the development of an outbreak population of I. pini.