Apple problems solved, sort of [UPDATED]Published 9:52am Monday, October 1, 2012 Updated 11:57am Monday, October 1, 2012
How are your apples this fall? Wormy, scabby, or have critters been chewing on the trunk? All of these problems can be avoided with a little bit of work.
Let’s start with wormy apples. Apple maggot is the top pest of apple growers. The damage is a dimple where the egg is laid and a brown tunnel the maggot makes in the flesh. If the apple has been attacked by multiple maggots, it will be inedible. One or two you can just cut out.
The flies emerge from the soil from July through September. They start laying eggs about a week later, and pierce the skin. The egg develops into the maggot that does all the damage.
The first line of defense against the damage is sanitation. Pick up wind falls at least twice a week and either bag, or bury them at least a foot deep. Thinning the apples to one or two per clump and bagging them prevents the fly from laying the egg on the fruit thus preventing damage.
A red trap hung one for every 100 apples will at least reduce the fly population. A red coke can covered with tanglefoot and half full of a mix of molasses and apple cider vinegar hung about 25 feet from the tree works quite well. Wipe bugs and debris off with vegetable oil as needed to keep the trap effective. You can also spray Surround At Home Crop Protectant on the fruit. This is a mineral substance that coats the apple. You will need to reapply this every two weeks and after every rain.
Apple scab is another problem. This is an ugly, sometimes devastating fungal disease that causes rough spots on the apple and can harm the tree. It starts with small dark green to brown spots on the fruit that eventually grow into black lesions. The leaves have the same appearance and turn yellow then fall off. Wet springs trigger the problem and if the whole summer is rainy, you are shafted.
Prevention again starts with sanitation. Pick up and dispose of fallen leaves by burning or bagging them as they are infectious.
Prune in February to open up the canopy for better circulation. Don’t plant apple trees too close together to promote air circulation. You can spray or dust the tree with a sulfur plant fungicide before the tree blooms. Or, Serenade garden spray may suppress apple scab. It’s a biological pesticide that works on both fungus and bacteria. If you have had this problem, and are planning on planting more apple trees, consider planting two resistant varieties – Honeycrisp and SnowSweet. The University lists Dayton, Freedom, Liberty, McShay, Pixie Crunch, Pristine, Redfree and William’s Pride as totally immune to apple scab.
If you have had critter damage to any thin barked tree, protect them with a commercial plastic trunk cover, or wrap them with hardware cloth.
Do remove the trunk cover in the summer as it retains heat and can cause the bark to heat up so much that it splits. Don’t be lazy and let the hardware cloth get tight and grow into the bark of the tree.
Bev Johnson is a master gardener for Otter Tail County.