The Best Way to Get Rid of Hemlock Wooly Adelgid on Mature Trees

Hemlock woolly adelgid is a small, aphid-like pest that causes damage to mature trees. According to the United States Department of Agriculture, this insect from Asia is a source of concern for the health of eastern hemlock and Carolina hemlock. Infestations have spread from one case across the country. Southern regions see tree death in three to six years, while tree death in the north occurs in four to ten years after an infestation. Getting rid of the hemlock woolly adelgid is essential for the life of your mature plant.

Things You'll Need

• Insecticide
• Ladder
• Garden hose

Instructions

1. Inspect the tree for signs of the hemlock woolly adegid. These insects go dormant during the summer months, yet come back to life when the weather cools down in the fall. Look for insects 1/16 inch long, with purplish-black to red-brownish bodies. The "wool" that they produce to protect their eggs is the most telltale sign of the insect's presence.

2. Check the tree for damaged wood, needle drop or dieback. As the pest feeds on the sap in trees, it releases toxins into the tree. The hemlock may start to take on a greenish-gray color that deviates from its usual shiny-green appearance. Determine the extent of the damage. Old trees have a lower rate of survival when infected with the pest.

3. Remove any bird feeders from your infected trees. The pest commonly travels on birds and infect nearby trees.

4. Spray the trees in the early spring or summer months. You can also wait for the pest to come out of dormancy in the fall. Use an insecticide that contains bifenthrin. Spray from the bottom of the tree to the top using a ladder.

5. Repeat the application of insecticide according to the directions. Choose days to spray that are free of rain or harsh weather.

Tips & Warnings

• Water infected hemlocks with 1 inch of water a week around the drip line of the tree. The drip line is the area directly underneath the tree's outer branches.

• Avoid fertilizing any tree that has become infected with hemlock woolly adelgid.

References

• Pennsylvania Department of Agriculture and Conservation: Hemlock Woolly Adelgid
• University of North Carolina: Recommendations for Hemlock Woolly Adelgid
• USDA: Hemlock Woolly Adegid