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John Fulton

John Fulton
Former County Extension Director

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In The Backyard

Horticulture columns and tips done on a timely basis

Tree and Shrub Leaf Problems

Posted by John Fulton -

We have had a relatively dry spring thus far in our area. This would indicate we should have less anthracnose in our good quality shade trees, but the damp period only needs to last a matter of hours. Currently most trees and shrubs have leaf problems. These can be from diseases such as anthracnose, injury from high winds and blowing debris, herbicide drift, or a combination of all the above.

In the case of anthracnose on shade trees, or apple scab on production and ornamental apples, one of the big things is the weather. This disease will continue to infect with night time temperatures below about 65 degrees and some wet weather. Granted, we have had nothing like the last two years, but we have had some wet weather. Symptoms include browning along the leaf margins and between the veins. The diseases often occur where there is less air movement such as the lower portions of the tree and toward the main trunk.

High winds have also dried things out and physically damaged tissue on tender leaves. Drying tissue also occurs along the leaf edges and between veins which carry water to the leaves. A good indicator of damage of this sort is having worse symptoms on one side of the tree, where the wind was directly hitting the leaves. Another way to check would be if you had a similar tree planted in a very protected location, then you could compare the two trees.

Herbicide drift is abundant again this year. Drift frequently occurs when we have hot, sunny conditions and experience vapors coming up off of treated areas. Not all the drift problems are initiated in a field across the road. Growth regulator herbicides can vapor drift for up to a mile and a half. These herbicides include 2,4-D, MCPP, and dicamba. These are used on corn fields, but also on lawns, ditches, pastures, and many other places. Injury can also come from your own lawn if you treated for broadleaf weeds, even using a weed and feed product. Sometimes the damage isn't from vapors, but can be from a heavy rain actually taking the product into the soil where it is taken in by the roots of trees and shrubs. Most herbicide injury would appear as distorted growth, including cupping, curling, or elongation of leaves.

What we are dealing with in many cases is the three-part whammy. There are disease symptoms, evidence of wind (environmental) damage, and evidence of herbicide injury as well. In all cases, there really isn't much you can do but wait it out. Water during dry periods to make sure there is adequate moisture. I wouldn't even fertilize, since that can make some herbicide drift situations worse with the growth regulators being encouraged. In most cases, there will be leaf drop. As long as there are good buds remaining, a new set of leaves should appear in four to six weeks. Some trees have shown dead tips this year. Those won't come back, but there will be additional growth from just below the dead areas.

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