Winter injury in sweet cherries in northwest Michigan, 2006
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Even though the winter was quite mild, some sweet cherries in northwest Michigan are exhibiting significant winter dieback. Most of the affected trees show whole or partial limb death and often include death of last year’s terminal growth. This winter injury is directly related to tree stress last season. Tree stress in 2005 was caused by a combination of severe drought, very heavy crop loads and hot weather. Ethephon applied under hot, dry conditions often resulted in midsummer leaf drop and gummosis. Generally, the ethephon induced injury was most evident in the portion of the canopy closest to the sprayer discharge. This combination of stress factors resulted in wood that could not survive even a relatively mild winter.
In trees, where terminal dieback is common, one concern is that this year’s crop of fruit will all be produced on spurs. Cherries produced on spurs depend, in part, on leaves from last year’s terminal growth to provide adequate carbohydrates to size the fruit. If fruit set is heavy, death of terminals will likely result in smaller fruit because the cherries just do not have the resources from those important terminal leaves.
Because of the advanced season, there are few management strategies that could be used at this stage. However, growers should try to minimize stress factors in 2006 in all orchards exhibiting symptoms of excessive dieback this spring: 1) Maintain a good overall nutrition program and apply N at higher than normal rates to help stimulate strong growth this season. 2) Maintain a spray program that will keep leaves on trees into the fall, and 3) Avoid further ethephon damage this season.