Spray Deposition from Ground‐based Applications of Carbaryl to Protect Individual Trees from Bark Beetle Attack

Abstract

Bark beetles (Coleoptera: Curculionidae, Scolytinae) are recognized as the most important tree mortality agent in western coniferous forests. A common method of protecting trees from bark beetle attack is to saturate the tree bole with carbaryl (1-naphthyl methylcarbamate) using a hydraulic sprayer. In this study, we evaluate the amount of carbaryl drift (ground deposition) occurring at four distances from the tree bole (7.6, 15.2, 22.9, and 38.1 m) during conventional spray applications for protecting individual lodgepole pine (Pinus contorta Dougl. ex Loud.) from mountain pine beetle (Dendroctonus ponderosae Hopkins) attack and Engelmann spruce (Picea engelmannii Parry ex Engelm.) from spruce beetle (D. rufipennis [Kirby]) attack. Mean deposition (carbaryl + alpha-naphthol) did not differ significantly among treatments (nozzle orifices) at any distance from the tree bole. Values ranged from 0.04 +/- 0.02 mg carbaryl m(-2) at 38.1 m to 13.30 +/- 2.54 mg carbaryl m(-2) at 7.6 m. Overall, distance from the tree bole significantly affected the amount of deposition. Deposition was greatest 7.6 m from the tree bole and quickly declined as distance from the tree bole increased. Approximately 97% of total spray deposition occurred within 15.2 m of the tree bole. Application efficiency (i.e., percentage of insecticide applied that is retained on trees) ranged from 80.9 to 87.2%. Based on review of the literature, this amount of drift poses little threat to adjacent aquatic environments. No-spray buffers of 7.6 m should be sufficient to protect freshwater fish, amphibians, crustaceans, bivalves, and most aquatic insects. Buffers >22.9 m appear sufficient to protect the most sensitive aquatic insects (Plecoptera).

Spruce Beetle Biology, Ecology and Management in the Rocky Mountains: An Addendum to Spruce Beetle in the Rockies

“…Insecticide applications are applied to all bole surfaces up to a height of ~11 to 15 m until runoff to ensure thorough coverage of the root collar and exposed roots. The amount of insecticide formulation (water and insecticide) applied varies with tree architecture, tree size, equipment, and applicator, among other factors, but ranges between ~15 to 30 L per tree [178][179][180]. Bole sprays are typically applied in the fall to avoid access issues in the spring and spring runoff affecting -no spray‖ buffers to protect non-target aquatic organisms.…”

Alternative timing of carbaryl treatments for protecting lodgepole pine from mortality attributed to mountain pine beetle

“…(e.g., bifenthrin and permethrin, among others) are available and effective. Application efficiency, the percentage of carbaryl applied that is retained on trees, ranges from~80 to 90% (Fettig et al, 2008). Carbaryl is an acetylcholinesterase inhibitor that prevents cholinesterase enzymes from breaking down acetylcholine, increasing both the level and duration of action of the neurotransmitter acetylcholine, which leads to rapid twitching, paralysis and ultimately death (Hastings et al, 2001).…”

“…(2) Many sites where carbaryl treatments are commonly applied (e.g., campgrounds) occur near intermittent or ephemeral streams associated with runoff from snowmelt limiting applications in spring due to label restrictions concerning the use of no-spray buffers to protect non-target aquatic organisms (Fettig et al, 2008). Trees within no-spray buffers are left untreated and therefore vulnerable to colonization by D. ponderosae.…”

Evaluations of emamectin benzoate and propiconazole for protecting individual Pinus contorta from mortality attributed to colonization by Dendroctonus ponderosae and associated fungi

“…While these treatments are widely used, they require transporting large equipment into remote areas, which can be problematic . Furthermore, concerns regarding the potential for spray drift to be deposited onto adjacent bodies of water are common, although evidence suggests drift poses little threat if appropriate no‐spray buffers are used . However, susceptible trees within these buffers are left untreated and are therefore vulnerable to colonization by D .…”