Emerald Ash Borer (EAB)
Since its detection in Detroit in 2002, EAB has wreaked havoc on millions of ash trees across 23 states and 2 provinces. EAB has been very destructive to native ash trees due to host naivety and lack of natural enemies. However, individual trees can be saved with insecticides.
Until recently, EAB has only been known to feed on true ash species (Fraxinus spp.). However, it has now been confirmed that white fringe tree can serve as a host as well.
Trees infested by EAB tend to show many symptoms. These can include thinning of the canopy, branch dieback, “D” shaped exit holes in the trunk and branches, excessive shoots in the crown and/or base of the tree, excessive wood pecker activity, bark splits and tunneling underneath bark. The adult beetles are smaller than the diameter of a penny, metallic green, and can be seen flying in early summer.
Adults emerge when black locust are in bloom, which usually occurs at the beginning of June. Adult beetles then feed on ash foliage for approximately two weeks before mating and laying eggs on the bark. Larvae hatch and burrow into the tree where they feed and form galleries just behind the bark. Once ready for pupation, larvae will burrow approximately another ½ inch or so into the wood. They overwinter either as larvae or pupae until spring.
Damage occurs during the larval stage. EAB feed and create their galleries in the living tissue just beneath the bark. Without this tissue, trees cannot actively move nutrients effectively and trees essentially starve to death. This process typically takes anywhere from 1-3 years, but varies depending on the condition of the tree.
Once EAB gets into an area, it is likely that nearly 100% of ash trees will be killed unless treated with insecticides. That’s not to say that all trees SHOULD be treated. The site location and health of the tree should be taken into consideration before the decision of investment in treatments. Another important factor to consider is the distance you are from the areas where EAB has been detected. In the Midwest, it is recommended that if you are within 10-15 miles of a detection zone that you begin to plan for treatment. Some experts claim that you should not be treating unless you are 5 miles within a detection zone. Either way, a management strategy should be in place if EAB is nearby.
There are four systemic insecticides that are recommended to treat EAB: imidacloprid, dinotefuran, emamectin benzoate, and azadirachtin. Though emamectin benzoate seems to be the most effective treatment against EAB (especially on larger trees), all four insecticides have been shown to be good tools.
For more information on EAB and insecticide options, please follow the links below:
Emerald Ash Borer in Colorado: https://www.colorado.gov/agplants/emerald-ash-borer
Insecticide Options for Protecting Ash Trees from Emerald Ash Borer: http://extension.entm.purdue.edu/EAB/PDF/NC-IPM.pdf
FAQs Regarding Potential Side Effects of Systemic Insecticides Used to Control EAB: http://www.emeraldashborer.info/files/Potential_Side_Effects_of_EAB_Insecticides_FAQ.pdf