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Apple discoloration, moles and grubs

By John Fulton

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[October 23, 2010]  Sooty blotch of apple -- Sooty blotch and flyspeck are caused by different fungi that commonly occur together on the same fruit. The sooty blotch fungus causes surface discoloration with black spots or blotches that can be a fourth of an inch or larger. These spots may run together, making the apple appear to be covered with something like charcoal dust.

This disease is more superficial than anything, since it is only on the skin. Vigorous rubbing or scrubbing will remove the black discoloration. If you want to be sure, you can always peel the apples.

This disease is most common with moderate temperatures and wet weather. Wet weather can include heavy dews that don't get dried out very well. Anything that cuts down on air circulation helps promote sooty blotch. Pruning and thinning fruit will help improve air circulation and lessen the disease problems.

The best chemical control program is to use a multipurpose fruit tree spray containing captan fungicide as a preventive. For this disease, it is recommended to begin by early June and continue the program until harvest. For the organic gardeners, sulfur will help some. However, it is not as good as the captan. Remember, many diseases are preventable in home fruit production, but they are not curable. Once you see the problem, it becomes a to-do list item for next year.

Moles and grubs

The number of problems from moles seems to be greatly increasing. This means the food sources are abundant. The major food sources for moles are grubs and earthworms. With the large increases in grubs in some areas due to the Japanese beetle larvae, there may be plenty of food available. The exact number of grubs necessary to cause damage to turf is dependent on the type of grass, the condition, the moisture available and other factors. Figure somewhere between six and 12 grubs per square foot of turf to cause damage. One mole feeding on those grubs can really raise havoc.

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The best way to get rid of moles is to remove their food source. While grubs are undesirable, the earthworms are beneficial. We have to decide on controlling a desirable part of a healthy lawn to use this approach. In the "good old days," we treated with diazinon insecticide. It controlled grubs, and it greatly reduced the earthworm populations. This solved the problem, when the moles then went to the neighbor's yard in search of food. With diazinon long gone from the homeowner market, most of the remaining products for grub control are not effective against earthworms. The main exception is carbaryl (Sevin), and it is only effective against the Japanese beetle grubs.

If you don't want to try to eliminate the food source, you are reduced to "folklore treatments," traps or poison baits. The folklore treatments work just often enough for someone to give them a little validity, but they often don't work for the next person who is trying to control moles. Some of these are Juicy Fruit gum, bubble gum, cigar smoke, moth crystals, and the list goes on and on. Traps can be effective, but they have to be set properly. The type of trap also makes a difference. The loop and scissors-type traps tend to be more effective than the plunger type. There are soft bait poisons on the market now that will do a decent job.

As the weather grows colder, the grubs will go deeper into the soil. This makes them harder to control, as does their larger size. We are about at the point where this will begin to occur. This leaves traps or poison baits. For poison baits, think about the food sources of the mole. They don't eat seeds, so poison peanuts may not be the best choice. The newer soft baits are similar in texture to worms or grubs. They're just like the old "creepy crawlers" we used to make with the rubber-type compound, and they will be more successful.

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

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