Issue 4, May 20, 2013

Emerald Ash Borer

Emerald ash borer continues to spread through the state. During the last year, it was first found in the Dixon, Galesburg, Kewanee, and Ogle County areas in north central and northwest Illinois. These were expected with the infestation in nearby Peru found in 2007. Similarly, infestations in Champaign and Livingston County are near established infestations. Only that found in a railroad yard area in Decatur represents a disjunct infestation. Hopefully, these represent a reduction in the spread of this pest on firewood, but it is too early to tell.

Now is an excellent time to treat for emerald ash borer. All three of the recommended systemic insecticides move into the leaves within just a few days after application. Adults feed on the edges of ash leaves soon after emergence. Mortality of these leaf-feeding beetles is a major mechanism of control and research indicates that this may be the only meaningful control achieved with imidacloprid. Uptake of systemic insecticides is quickest at this time of year as transpiration is most active in young leaves with sufficient soil moisture.

Adult emergence is typically expected in central Illinois during the first week of June and would be expected in late May in the southern Illinois infested areas of Effingham and Salem. However, we are currently about one week behind a typical spring, so there is probably an extra week to apply controls unless we experience unseasonably warm weather in the next couple of weeks. Emergence in northern Illinois is not expected until mid-June and may be a week later this year due to the late spring.

Arborists, landscapers, and other profession­als can apply emamectin benzoate (Tree-age) as a trunk injection, imi­dacloprid (Merit, Imicide, IMA-jet, Xytect, and others) at the highest labeled rate as a soil and trunk injec­tion and soil drench, and dinotefuran (Safari) as a trunk spray. Do not apply imidacloprid as a drench into mulch or other dead organic matter because it adsorbs onto these materials, making it unavailable for root uptake.

Applications of imidacloprid and dinotefuran should be made annually except that emamectin benzoate needs to be applied only every two to three years. Control is more effective on smaller trees, those with a trunk diameter of less than two feet, but consistent, effective control has been achieved with emamectin benzoate on trees up to 44 inches dbh . Application is recommended to trees within 15 miles of a known infestation. Even infested trees showing dieback survive and show signs of recovery in the form of normal stem and leaf growth with the above insecticide recommendations if the dieback is not too severe.

Additional information on emerald ash borer life cycle, scouting, and damage is available on our reproducible fact sheet at (Phil Nixon)

Phil Nixon

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