- Imidacloprid and dinotefuran are effective treatments for hemlock woolly adelgid.
- DIY applications are possible but require careful adherence to label instructions.
- Coordinate with neighbors for comprehensive treatment plans.
- Professional help is recommended for trees near water or in sensitive areas.
- Early treatment between April and October yields the best results.
Effective Treatments for Hemlock Woolly Adelgid
Hemlock woolly adelgid, an invasive insect native to Asia, poses a significant threat to hemlock trees in Michigan. According to the source, infestations have been reported in counties such as Allegan, Antrim, Benzie, and Washtenaw. The Michigan Department of Natural Resources (DNR) emphasizes the importance of planning spring treatments to combat this pest. Products containing imidacloprid or dinotefuran as active ingredients are highly effective. Imidacloprid moves slowly through trees, providing protection for at least four years, while dinotefuran acts faster, making it ideal for heavily infested trees but requiring reapplication every one to two years.
DIY Treatment Options
Many landowners can apply imidacloprid or dinotefuran themselves. These products are available at garden supply stores in liquid or granular forms. Application involves placing the product near the tree trunk for root absorption. The optimal treatment period is between early April and late October, when soil moisture is moderate. Following label instructions, wearing safety gear, and avoiding environmental contamination are crucial. Some products have annual application limits, so a multiyear plan or professional assistance may be necessary.
Coordinating with Neighbors
Since hemlock woolly adelgid can spread to neighboring properties, coordinating treatment plans with neighbors is advisable. Even asymptomatic trees are likely to become infested over time. Collaborative efforts ensure comprehensive protection and reduce the risk of reinfestation.
When to Call a Professional
Licensed pesticide applicators offer a broader range of treatment options, especially for trees near water bodies or in areas with a high water table. Trunk injections or bark treatments may be necessary to protect the environment and other plants. Professionals licensed in ornamental (3B) or forestry (2) categories can provide tailored solutions.
Post-Treatment Monitoring
After treatment, hemlock woolly adelgid’s white ovisacs may persist. For dinotefuran, check new growth in late fall or winter for signs of infestation. With imidacloprid, wait a year to assess effectiveness. Annual monitoring is essential, and reapplication may be needed based on the product used.
Identifying Hemlock Trees
Accurate identification is critical. Eastern hemlock trees have drooping branches, flat needles with white stripes underneath, and small papery cones. Look for round, white ovisacs on the undersides of branches. If unsure, consult the Michigan Invasive Species Program’s identification guide.
Reporting Infestations
Report infested hemlock trees to the Midwest Invasive Species Information Network or the Michigan Department of Agriculture and Rural Development. Include the location and photos of infested branches for confirmation. Avoid collecting samples to prevent further spread.