Pesticides can be an important tool for protecting trees from spruce beetle attack. However, pesticides are not always the right tool for every tree or every property or every person. It is important to understand pesticides when making decisions about whether or not to treat a tree. These products require correct timing and proper application to be successful. Pesticide applications are effective when applied properly per the label recommendations. Pesticide failures are usually the result of improper timing, improper application, inadequate coverage, or poor product mixing.
Pesticide applications for spruce beetle are preventive only and should be used only on trees that are uninfested at the time of application. Once a tree has been attacked, there is very little that can be done for the tree because of the nature and location of the damage. Plan ahead to protect uninfested trees on your property. Additionally, there are no pesticide products that can be applied to firewood to kill spruce beetles.
Pesticide applications are usually saved for use on high-value ornamental trees or in situations where health and safety could be a concern, such as in a campground or picnic site of a recreational area.
Several tree care and pest control companies offer tree protection services for spruce beetle. Some products may also be available to general consumers, but they often require additional equipment for application, a variety of personal protective equipment items, and are sold in concentrate quantities meant for multiple applications. For individual trees on your property, hiring a certified pesticide applicator may make more financial sense than investing in a lot of equipment or product.
If you choose to DIY your spruce beetle treatment, make sure you read and follow the pesticide label. A pesticide label is a legal document. Use of the product should comply with all directions and restrictions listed on the label. You can read more about homeowner pesticide use from the Alaska Department of Environmental Conservation Pesticide Program.
If you have questions about pesticide use or specific products for spruce beetle prevention call your local Cooperative Extension Service office.
Pesticide active ingredients are the components of the product that act on the pest. Active ingredients currently registered for use in Alaska against spruce beetle are: abamectin, carbaryl, emamectin benzoate, and members of the pyrethroid group of products. Carbaryl and some pyrethroids have been extensively studied for use against spruce beetle in Alaska. Table 2 (below) lists active ingredients effective against spruce beetle along with common products containing them and information about application.
Carbaryl and pyrethroid products are formulated to be sprayed onto spruce trees, while abamectin and emamectin benzoate are systemic products formulated to be injected directly into the tree. The injection technology and injectable products are newer to the market than sprays and have been researched less, especially in Alaska. Studies of these newer products were initiated in 2018 to evaluate their use in Alaska and to provide specific recommendations for Alaskan conditions.
Sprays
Spray products should be applied to the trunk of the tree from the ground up, at least 25 feet. Ideally, the trunk would be treated until the diameter is less than 5 inches. If treating only to a certain height, know that beetles may attack above the spray line if the diameter remains suitable. Sprays should be made in the spring, before the adult flight period begins.
Injections
Systemic products are injected directly into the trunk and must move throughout the tree. This movement can take time. Research in other spruce beetle systems shows that products containing emamectin benzoate needed to be applied approximately 12 months prior to infestation to be effective (Fettig et al 2017). While these injectable products have been successful in other spruce beetle systems, recent studies in Alaska have not shown consistent tree protection against spruce beetles by these products. At this time, we do not recommend the use of injectable pesticides to protect trees from spruce beetles.
| Active Ingredient | Common product(s)* | Common application method | Notes |
|---|---|---|---|
| Carbaryl | Sevin SL | Spray | Has been shown to be effective for 2 field seasons in Alaska |
| Permethrin | Astro® | Spray | Has been shown to be effective for 1 field season in Alaska |
| Emamectin benzoate | Tree-age® G4; Boxer™ | Injection | Not recommended in Alaska |
| Abamectin | Abacide™ 2 | Injection | Not recommended in Alaska |
| Table 2: Active ingredients in pesticides registered for spruce beetle control in Alaska with examples of product names, application methods, and notes on applications. * The trade names listed here are not an endorsement of these products. They are used as common examples. |
Additional important things to know about pesticide use for spruce beetle:
- Products not registered as pesticides should not be used to control spruce beetle. There are no home remedies that are proven effective against these pests.
- Some products have specific sites that they can be applied to. For instance some products are labeled for ornamental trees but not forest trees or vice versa. Make sure you know to what sites your product can be applied.
- Read and understand the pesticide label. Pesticide labels are important documents with invaluable information about how to use the product safely and effectively. More information about pesticide labels can be found online from the National Pesticide Information Center website and PennState Extension.
Citation
Fettig, C. J., D. C. Blackford, D. M. Grosman, A. S. Munson. 2017. Injections of emamectin benzoate protect Engelmann spruce from mortality attributed to spruce beetle (Coleoptera: Curculionidae) for two years. Journal of Entomological Science. 52(2):193-196.