Arboriculture & Urban Forestry 33(5): September 2007 319 pouch at 10 or 15 m (11 or 16.5 yd) centers (Borden et al. 2003; Progar 2003, 2005; Bentz et al. 2005). The pouch has been registered as a pesticide with the U.S. Environmental Protection Agency since 2000 and was registered with Cana- da’s Pest Management Regulatory Agency in 2006. In the spring of 2005, Pherotech was looking for opportunities to conduct operational trials with the new Canadian product. The senior author (JHB) was therefore pleased to receive a request from the second author to test the pouch at Lac le Jeune. MATERIALS AND METHODS Figure 1. Map of Lac le Jeune, B.C., showing five subdi- visions. It has long been known that verbenone could deter attack by the mountain pine beetle in forest stands treated with slow-release bubble-cap devices affixed to trees (Amman et al. 1989; Lindgren et al. 1989) or aerially applied pheromone- impregnated plastic pellets (Shea et al. 1992). However, it was not widely used as a pest management tool because of inconsistent results on different species of trees, from one year to the next, and in different geographic areas (Bentz et al. 1989; Lister et al. 1990; Gibson et al. 1991; Shea et al. 1992; Amman and Lindgren 1995). Eventually, three approaches were taken to resolve the problem of inconsistency: combining verbenone with repel- lent nonhost angiosperm bark volatiles, increasing the dose, and integrating repellent and attractive semiochemicals in a push–pull tactic (Borden et al. 2006). Huber and Borden (2001) found that combining verbenone bubble caps with a seven-component nonhost volatile blend provided almost complete protection of treated pairs of lodgepole pines com- pared with almost 100% successful attack on nearby un- treated pairs. However, because of cost and regulatory con- cerns, Borden et al. (2006) used a simplified three-component blend. This blend was effective alone in deterring attack when deployed at 16 points in a 10 m (11 yd) grid in 40 × 40 m (44 × 44 yd) plots; however, when combined with verbe- none, it did not improve on the deterrent effect of verbenone alone. Raising the dose of verbenone approximately sixfold over the 4 mg per day release rate from bubble caps improved the efficacy and consistency of verbenone in treated stands (Progar 2003; Bentz et al. 2005). The high-dose verbenone pouch (Pherotech International Inc., Delta, B.C., Canada; trade name “No Vacancy Pack”) releases verbenone from a polyurethane substrate at approxi- mately 25 mg (0.4 gr) per 24 hr at a constant 20°C (68°F) and 100 mg (1.5 gr) per 24 hr at 30°C (86°F). It was effective in deterring attack in small plots or stands grid-treated with the The residents of Lac le Jeune raised over $9000 for purchase of pouches for treatment of residential properties, and addi- tional funding was obtained from Dr. Lorraine Maclauchlan of the B.C. Ministry of Forests and Range, Kamloops Region, for treatment of adjacent Crown land. To reduce the risk of attack from within their properties, the residents removed most of the infested trees (for exceptions, see “Results” and “Discussion”). However, no infested trees were removed from any property in the Little Lake subdivision, which is owned entirely by seasonal residents. In the third week of July 2005, when flight and attack by emergent beetles appeared imminent, a group of volunteer residents deployed 1191 pouches on private property under direction of the second author. Pouches were stapled to the north face of trees at maximum reach from the ground, ap- proximately 2 to 2.5 m (2.2 to 2.75 yd). The intent was to space pouches approximately 15 m (16.5 yd) apart in a more or less even grid. However, perhaps realizing that the danger lay outside their properties, the volunteers tended to concen- trate placement of pouches near boundaries facing the un- treated infestations on Crown forest land or the park. In the end, the desired density of pouches was achieved (Table 1) with a mean density of 53.6 pouches/ha (21.7 pouches/A) over the four treated subdivisions [15 m (16.5 yd) centers would be 44.4 pouches/ha (18.0 pouches/A) and 10m(11 yd) centers would be 100 pouches/ha (40.5 pouches/A)]. An ad- ditional 197 pouches were deployed in a 25 m (27.5 yd) wide buffer strip within the Crown forest bounding the treated subdivisions. Some pouches were placed slightly beyond the 25 m (27.5 yd) strip. The efficacy of the verbenone treatment was evaluated during a 7-day period beginning on 15 October 2005. Every lodgepole pine with a diameter at breast height [dbh1.3 m (1.4 yd)] 17.5 cm or greater (7 in) was examined for attack in each of the 95 residential properties in the four subdivisions, in the verbenone buffer strips, and in an untreated “control” block extending into the Crown forest at least 100 m (110 yd) beyond the buffer strip (Table 1; Figure 2). Because the con- trol plot in the Crown forest adjacent to the Lookout subdi- vision was only 50 m (55 yd) wide, the buffer and control zones were not evaluated separately. The respective total ar- ©2007 International Society of Arboriculture
September 2007
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