This week's highlights -- or lowlights

By John Fulton

[May 19, 2009]  With the type of weather we have had, it should have been expected many different diseases would come our way this spring. Well, they are here. Here are some shorts on the past week and some of the items found without looking too hard.

Peach leaf curl is caused by a fungus on trees in the stone fruit family. This would include mainly peaches and plums. It is rather striking with the bright red swellings on the green leaves. This disease can only be prevented with a dormant-time application of a fungicide on your trees. Seeing it now means that you probably should have sprayed before the buds began to swell (meaning before leaves actually came out).

Anthracnose starts as dead leaf areas between leaf veins or on the tips of leaves. When severe enough, leaves will fall. The good news is that it rarely harms trees. If enough leaves drop, a new set comes out in four to six weeks and we start all over. The next set of leaves may also get the disease, but they may not. Infection can continue with weather favorable to the disease and when nighttime temperatures stay under 65 degrees. Treatments when you see the symptoms of this disease are simply wasted time and money.

Apple scab is a disease similar to anthracnose and can cause premature leaf drop in apples and crab apples. If you are on a regular spray schedule for fruit trees, it should prevent most of the problems. You could also spray crab apples this way, but you would have to weigh the cost and benefit since no fruit production is involved.

Many people are reporting holes in tree trunks. These holes are round and in a pattern either around or up and down on tree trunks. They are also usually found in a tree that has high sap flows, such as maples, gums or evergreens. These holes are caused by yellow-bellied sapsuckers. About the time we notice the holes, the birds are gone. They migrate and only bless us with their presence about two months in the spring (around May) and again in the fall (around September). These holes can cause injury to the tree by allowing a place for insects and disease to get in and can cause death if they completely girdle trees.

Control is very difficult and consists of trying to scare the birds with pie pans, whirlybirds, rubber snakes or other items that make sound or sight. If damage in an area of the tree trunk is severe, you can wrap burlap around that portion to protect it. The sticky-type products, such as Tanglefoot, would also have some effect but might cause problems for some of the non-sapsuckers in the area.

Apple and pear trees are also having their problems. There is a large amount of tip dieback in some varieties, and this is probably fire blight. Look for a shepherd's crook at the tip of the affected areas as a clue it is fire blight. Fire blight is a bacterial disease; therefore, there is little chance for you to treat it. The common treatment in commercial operations is streptomycin, but it has to be applied before symptoms appear. Bordeaux mixture can also help prevent the disease. Prune out disease cankers when dormant. This disease cost Illinois its pear industry.

[By JOHN FULTON, University of Illinois Extension, Logan County]