Efficacy of antiaggregants for the pine engraver, Ipspini (Coleoptera: Scolytidae)

Abstract

The responses of pine engravers, Ipspini (Say), in British Columbia to ipsdienol-baited traps containing low, medium, and high dose rates of the antiaggregants verbenone and ipsenol, released from impregnated polyethylene and polypropylene beads, respectively, remained significantly lower than responses to ipsdienol-baited control traps throughout the spring. During the summer, the responses remained low only in traps containing medium and high dose rates of impregnated beads. Antiaggregant treatment densities of 100 and 400 bubble cap release points per hectare reduced the numbers of pine engravers caught in ipsdienol-baited, multiple-funnel traps by 66.1 and 76.8%, respectively. In 50 × 50 m thinning-simulation plots treated with a broadcast distribution of antiaggregant-impregnated beads in 1990, 32.9% of the felled lodgepole pines, Pinuscontorta Dougl., were attacked; in untreated control plots, 53.1% were attacked. The mean attack density per square metre of available bark surface in the treated plots (1.3) was significantly lower than that in the untreated plots (1.9); however, where attack occurred there was no difference (8.8 and 9.4 attacks/m2, respectively). In a 1991 experiment, verbenone- and ipsenol-impregnated beads were applied to 15 × 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 ground surface per day, and at double these rates. For three treatments, low and high rates 3 weeks prior to the first attack by I. pini and a high 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 control plots. The results of these experiments suggest that a timely application of broadcast antiaggregants would prevent the development of an outbreak population of I. pini.