You can protect your ash trees from emerald ash borer with the right treatment plan – Chicago Tribune –

We have been on a two-year treatment schedule to protect our ash trees from emerald ash borer and have been fortunate to keep nearly all the trees growing and healthy. Recently we heard that it was possible to extend to a three-year treatment schedule and was wondering if this would be OK for our ash trees to save on costs?

— Sam Goldstein, Libertyville

Your contractor is most likely using a trunk injection of TREE-äge™ (emamectin benzoate) to treat your ash trees for control of emerald ash borer. You would lose your ash trees to this insect without these regular treatments. This is an insect pest that requires regular insecticide applications for control. Recent studies have shown that you can extend to a three-year treatment schedule even though the label recommends two. This will reduce your costs while adequately protecting your trees.

There are some things to consider before making the change. There are not many ash trees left in the Chicago area landscape, so there is probably low emerald ash borer activity in the vicinity of your garden. If there was high pressure from emerald ash borer locally, it would be safer to stay with a two-year treatment schedule. If any of your remaining ash trees are of particularly high value to you or are under stress from other factors such as drought, keeping the two-year treatment plan is a good idea. Since you have been treating your trees on a regular basis for several years, the transition to a three-year treatment plan should be OK for you. It’s best to start a new treatment program for an ash tree with a two-year treatment plan before transitioning to a three-year program.

For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.