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Friday, Apr. 5th 2013

Forest Health Newsletter

Spring has arrived – – finally! Here are a few updates on the timing of spring warm-up and a couple tree health issues.

As we all know,spring warm-up is late this year. How late? Based on phenological indicators (blooming, budbreak, etc.) that we monitor in the Columbia area, we are running about 1.5 to 2 weeks behind averages for several recent years. Star magnolias and forsythias have just started blooming here. At this time last year, we were running about three weeks ahead of average for plant phenology. That’s about a month difference in timing between 2012 and 2013!

Where emerald ash borers are present, adults can be expected to start emerging after peak bloom occurs on Van Houtte Spirea and near the start of black locust bloom. Based on accumulated degree days so far and using past temperature averages, we can make rough estimates of the timing of EAB emergence. In the counties where EAB has been detected in southeast Missouri, adult emergence could be expected to start approximately in the 2nd week of May. In the Kansas City area, emergence could be expected to start about the 3rd week of May. This could all change of course if we get unusually hot or cold temperatures. After emergence starts, EAB adults will be present roughly through July.

The risk of oak wilt infection goes up in the spring when sap-feeding beetles carrying the fungus responsible for the disease visit fresh wounds on oak trees. Oaks also become more susceptible to infection beginning 1-2 weeks before leaf-out. Follow the rule “Don’t prune in April, May and June” and avoid making pruning wounds or other injuries on oaks in the spring. Tree wound dressings applied to any fresh wounds on oaks during this time will help protect the tree from oak wilt.

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University of Missouri Extension Master Gardener Program