248 Fettig et al.: Effectiveness of Permethrin Plus-C and Carbaryl High-value trees such as those located in residential, rec- reational (campgrounds), or administrative sites are particu- larly susceptible to bark beetle attack as a result of increased amounts of stress associated with drought, soil compaction, mechanical injury, or vandalism (Haverty et al. 1998). Re- gardless of landowner objectives, tree losses in these unique environments can have a substantial impact (McGregor and Cole 1985). The value of these trees, the cost of removal, and the loss of aesthetics may justify protecting individual trees until the main thrust of an infestation subsides. This situation emphasizes the need for assuring that effective insecticides are available for individual tree protection. Carbaryl is considered one of the most effective and envi- ronmentally safe insecticides used to prevent bark beetle at- tacks (Hastings et al. 2001). In the past, several formulations have been evaluated for protection of individual trees from attack by western bark beetle species, primarily D. brevico- mis and D. ponderosae. The effectiveness and residual life of 1.0% and 2.0% carbaryl (Sevimol; Bayer Environmental Science, Montvale, NJ) for preventing successful attack of P. ponderosa by D. brevicomis have been demonstrated (Hall et al. 1982; Haverty et al. 1985). The effectiveness of 2.0% carbaryl (same formulation) was also confirmed for protect- ing P. contorta from D. ponderosae attack (Gibson and Ben- nett 1985; Page et al. 1985; Shea and McGregor 1987). These and other studies (Smith et al. 1977; McCambridge 1982) led to the registration of 2.0% Sevimol as a preventive spray. A 1.0% suspension of carbaryl (Sevimol and Sevin SL; Bayer Environmental Science, Montvale, NJ) was effective for protecting P. contorta from D. ponderosae attack in Mon- tana for at least 1 year. A 2.0% suspension was effective in protecting P. ponderosa from D. brevicomis attack in south- ern Idaho for 1 year (Haverty et al. 1998). Shea and McGre- gor (1987) evaluated the efficacy of 0.5%, 1.0%, and 2.0% carbaryl (Sevimol and Sevin XLR) and found all concen- trations and formulations were effective for protecting P. contorta from D. ponderosae attack for at least 1 year. In south central Alaska, Werner et al. (1986) reported that car- baryl protected white, Picea glauca (Moench) Voss, and Lutz, P. glauca X lutzii Little, spruce from spruce beetle, D. rufipennis Kirby, attack for three field seasons. Berisford et al. (1981) reported that 2.0% carbaryl was ineffective for preventing southern pine beetle, D. frontalis Zimmerman, attack, which later was linked to tolerance in that beetle as- sociated with an efficient conversion of carbaryl into metabo- lites and a rapid rate of excretion (Zhong et al. 1995). Several pyrethroid insecticides are effective for protecting individual trees from bark beetle attack. In laboratory and cut-bolt bioassays, permethrin was shown to be highly toxic to D. brevicomis, D. frontalis, and D. ponderosae (Hastings and Jones 1976; Hastings et al. 1981; Smith 1982). Shea et al. (1984) examined the effectiveness of permethrin (Pounce; FMC Corporation, Philadelphia, PA) at three rates—0.1%, ©2006 International Society of Arboriculture 0.2%, and 0.4%—for protecting P. ponderosa from D. brevi- comis attack and reported that 0.2% and 0.4% provided pro- tection for ≈4 months. Haverty et al. (1998) examined several rates of esfenvalerate and cyfluthrin for protecting P. pon- derosa and P. contorta from D. brevicomis and D. pondero- sae attacks, respectively. In the Sierra Nevada, esfenvalerate (Asana XL; E.I. du Pont de Nemours and Company, Wil- mington, DE) applied at 0.025% and 0.05% provided protec- tion of P. ponderosa for a full summer (Haverty et al. 1998). In Montana, 0.006% and 0.012% esfenvalerate were found to be ineffective for protecting P. contorta from D. ponderosae attack. However, the 0.025% rate was effective for a single field season. Cyfluthrin (Tempo 20 WP; Bayer Environ- mental Science, Montvale, NJ) applied at 0.025% provided protection of P. ponderosa for one field season in Idaho, but not in California (Haverty et al. 1998). All three cyfluthrin treatments, 0.025%, 0.05%, and 0.1%, were highly effective for protecting P. contorta for two field seasons (Haverty et al. 1998). DeGomez et al. (2006) reported that 0.19% permethrin plus-C (Masterline; Univar USA, Inc., Austin, TX) and 0.06% bifenthrin (Onyx, FMC Corporation, Philadelphia, PA) were effective for protecting P. ponderosa bolts from successful engraver beetle, Ips spp., attacks. Hall (1984) ex- amined the efficacy of carbaryl, chlorpyriphos, fenitrothion, and permethrin for preventing red turpentine beetle, D. valens LeConte, attack and reported that only 2.0% and 4.0% car- baryl and 4.0% fenitrothion were effective. The objectives of this study were to: 1) confirm the effi- cacy of the registered rate of carbaryl (Sevin SL) for pro- tecting P. ponderosa from D. brevicomis attack (California) and P. contorta from D. ponderosae attack (Montana); 2) assess the efficacy of Sevin SL for protecting P. edulis from I. confusus attack (Arizona); and 3) assess the efficacy of permethrin plus-C (Masterline) for protecting individual, high-value trees from bark beetle attack. MATERIALS AND METHODS This study was conducted at three locations: 1) Shasta County, California (40.88°N, 121.65°W; 975 m [3,199 ft] elevation), 2) Beaverhead-Deerlodge National Forests, Mon- tana (45.92°N, 121.37°W; 1966 m [6,450 ft] elevation), and 3) Coconino County, Arizona (35.23°N, 111.51°W; 2104 m [6,902 ft] elevation). At each site, four treatments were ap- plied to each of 24 (AZ) and 30 (CA and MT) randomly selected trees: 0.2% a.i. permethrin plus-C (Masterline), 1.0% (AZ) and 2.0% (CA and MT) a.i. carbaryl (Sevin SL), and two separate untreated controls. One control group was used to assess bark beetle pressure during each of two field seasons (2004–2005). In Arizona, a single set of control trees was used during both field seasons. Once insecticides were mixed in the sprayer, and before treatments began, two tank samples were collected and returned to the laboratory for
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