**Acknowledgements**

Fettig et al. [14] reported mean deposition values from 0.04 ± 0.02 mg carbaryl/m2 at 38.1 m

fected the amount of deposition. Deposition was greatest 7.6 m from the tree bole and de‐ clined quickly thereafter. Approximately 97% of total spray deposition occurred within 15.2 m of the tree bole (Fig. 6). To evaluate the potential risk to aquatic environments, the authors converted mean deposition to mean concentration assuming a water depth of 0.3 m selected to represent the average size of lotic systems, primarily small mountain streams, adjacent to many recreational sites where bole sprays are often applied [14]. No adjustments were made for the degradation of carbaryl by hydrolysis, which is rapid in streams or for dilution by natural flow. Comparisons were made with published toxicology data available for select aquatic organisms. No-spray buffers of 7.6 m are sufficient to protect freshwater fish, am‐ phibians, crustaceans, bivalves and most aquatic insects. In laboratory studies, carbaryl was found to be highly toxic to stoneflies (Plecoptera) and mayflies (Ephemeroptera), which are widely distributed and important food sources for freshwater fishes, but negative impacts in field populations are often short-lived and undetectable several hours after contamination [55]. No-spray buffers >22.9 m appear sufficient to protect the most sensitive aquatic insects

An advantage of tree injections is that they can be used on environmentally-sensitive sites as these treatments represent an essentially closed system and therefore little or no contamina‐ tion occurs outside of the tree. However, following injection residues move within the tree and are frequently detected in the foliage [e.g., 44,56-57], which could pose a risk to decom‐ posers and other soil fauna when needles senesce. This has been shown for imidacloprid in maple [57], but injections of emamectin benzoate in pines appear of little risk. For example, [56] reported emamectin benzoate was not detected in the roots or the surrounding soil, but was present at 0.011–0.025 µg/g in freshly fallen pine needles. However, levels gradually de‐

The results of the many studies presented in this chapter indicate that preventative applica‐ tions of insecticides are a viable option for protecting individual trees from mortality due to bark beetle attack. Bole sprays of bifenthrin, carbaryl and permethrin are most commonly used. Several formulations are available and effective if properly applied. Residual activity varies with active ingredient, bark beetle species, tree species and associated climatic condi‐ tions, but generally one to three years of protection can be expected with a single applica‐ tion. Recent advances in methods and formulations for individual tree injection are promising, and further research and development is ongoing. We expect the use of tree in‐ jections to increase in the future. In general, preventative applications of insecticides pose little threat to adjacent environments, and few negative impacts have been observed. We hope that forest health professionals and other resource managers use this publication and other reports to make informed, judicious decisions concerning the appropriate use of pre‐ ventative treatments to protect trees from mortality due to bark beetle attack. Additional

clined to below detectable thresholds after 2 months [56].

at 7.6 m. Overall, distance from the tree bole significantly af‐

to 13.30 ± 2.54 mg carbaryl/m2

486 Insecticides - Development of Safer and More Effective Technologies

such as stoneflies.

**8. Conclusions**

We thank Stanislav Trdan (University of Ljubljana) and Romana Vukelic and Danijela Duric (InTech) for their invitation to contribute and guidance during the publishing process. Nu‐ merous colleagues from Arborjet Inc., BASF, Bayer ES, Bureau of Land Management (U.S.), FMC Corp., Fruit Grower's Supply Co., Mauget Inc., Nevada Division of Forestry, Sierra Pa‐ cific Industries, Southern Ute Reservation, Syngenta Crop Protection, Texas A&M Forest Service, Univar USA Inc., University of Arizona, University of California, University of Georgia, and USDA Forest Service have contributed to the success of much of the research discussed in this chapter. We are thankful for their support and helpful insights.

This publication concerns pesticides. It does not contain recommendations for their use, nor does it imply that the uses discussed here have been registered. All uses of pesticides in the United States must be registered by appropriate State and/or Federal agencies. CAUTION: Pesticides can be injurious to humans, domestic animals, desirable plants, and fish or other wildlife—if they are not handled or applied properly. Follow recommended practices for the disposal of surplus pesticides and their containers.
