Arboriculture & Urban Forestry 33(3): May 2007 163 in preventing successful Phloeosinus attack. In fact, no stud- ies have been published on preventive treatments for any Phloeosinus species. in the southwestern United States. Sec- ond, the duration of efficacy for many of these preventive sprays remains untested. In previous studies, Hall et al. (1982) and Hastings et al. (2001) concluded that many of the carbaryl-based products may have residual activity of any- where from 3 to 27 months. Finally, because there are doubts regarding the reregistration of carbaryl products, new insec- ticides should be tested (Haverty et al. 1998). We evaluated several preventive insecticide sprays to ad- dress the issues associated with these regional and species differences in insecticide performance (DeGomez et al. 2006). The purpose of this study was to test the efficacy of carbaryl (Sevin SL, Bayer Environmental Science, Montvale, NJ, U.S.) along with two synthetic pyrethroids, bifenthrin (Onyx, FMC Corporation, Philadelphia, PA, U.S.) and per- methrin (Permethrin Plus C, Univar, Austin, TX, U.S.) in precluding Phloeosinus colonization of one-seed juniper and Arizona cypress. MATERIALS AND METHODS We conducted two experiments in the summer of 2004 to evaluate the efficacy of preventive insecticide treatments for protecting Arizona cypress and one-seed juniper from attack by Phloeosinus bark beetles. We generally followed the guidelines set forth by Shea et al. (1984) and Haverty et al. (1998) for testing insecticides against Dendroctonus bark beetles. Bolts were used as surrogates for standing live trees be- cause tree baits (i.e., pheromone lures or host tree com- pounds) for Phloeosinus spp. have not been developed. Also, Phloeosinus beetles are known to be attracted to and colonize fresh slash (Furniss and Carolin 1977), so we reasoned that using bolts would be the best method for successfully con- ducting a rigorous test of the preventive insecticides. Arizona Cypress Experiment This experiment was conducted approximately 2 km (1.2 mi) south of Pine, Arizona, on the Tonto National Forest (N34°21.75, W111°25.72) between 1645 and 1707 m el- evation (5,429 to 5,633 ft) from 14 June to 10 August 2004. The efficacy of four preventive spray formulations was tested: 0.19% permethrin with cellulose additive (Permethrin Plus C), 0.03% and 0.06% bifenthrin (Onyx), and 2.0% carbaryl (Sevin SL). Bolts 1 m (3.3 ft) in length, with 7 to 20 cm (2.8 to 8 in) diameters, were cut from freshly felled pole-sized Arizona cypress trees. Bolts were arranged in a randomized block design; each block consisted of four treat- ment bolts plus one control bolt placed horizontally on the ground with 0.25 m (0.83 ft) between the bolts and fresh host tree slash surrounding the block. Treatment blocks (24 rep- licates) were located next to existing roads with 50 m (165 ft) between blocks. To ensure that a sufficient number of beetles would be present in the vicinity of each block, we selected a stand containing Arizona cypress with epidemic levels of Phloeosinus cristatus. The insecticide sprays were applied to the point of runoff to bolts lying on the ground with an Ortho (Scotts Company, New York Mills, NY, U.S.) lawn and gar- den pesticide sprayer. Each insecticide formulation had its own sprayer to prevent cross-contamination. Approximately 200 mL (≈6 fl oz) of formulated insecticide was used on each bolt. For the formulations of carbaryl, we tested the water for pH and added vinegar to bring the water to a pH of 7.0. Bark beetle attacks, defined as discreet piles of boring dust, were recorded weekly for ≈8 wk until 80% of the control bolts had sustained attacks (10 August 2004). At this point, all the bolts were moved from the study site to a shaded area behind the Northern Arizona University (NAU) greenhouse (Flagstaff, AZ). Once beetle exit holes were observed, the bolts were completely peeled and the P. cristatus galleries present were counted. Nuptual chambers and egg and larval galleries were all counted as a single gallery. One-Seed Juniper Experiment The experiment was conducted on the NAU/Arizona State Land Department Centennial Forest north of Flagstaff, Ari- zona (N35°32.77, W111°45.52) at an elevation of 1920 to 1950 m (6,336 to 6,435 ft) from 4 April to 20 July 2004. This Table 1. Efficacy of preventive spray formulations in protecting Arizona cypress bolts from attack by Phloeosinus cristatus bark beetles. P value for rejectingz Insecticide Control I — No. of Arizona Cypress Bolts Tested Failuresy 23 Bifenthrin 0.03% 24 Bifenthrin 0.06% 24 Permethrin 0.19% 24 Carbaryl 2.00% 24 23 11 8 13 18 13 16 11 6 Successes Percent success 0 0.0% 54.2% 66.7% 45.8% 25.0% zRejection is more accurately described as “failing to accept the null hypothesis, H0.” yTreatment failure defined as presence of P. cristatus galleries in an individual bolt. ©2007 International Society of Arboriculture <0.001 <0.001 <0.001 <0.001 <0.001 binomial test Ho proportion of successes was to: 0.90 0.80 <0.001 0.002 0.084 <0.001 <0.001 that 0.70 <0.001 0.071 — 0.009 <0.001
May 2007
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