How to Keep Apple Trees Happy in the Summer

August 14, 2012

Here are some important tips for keeping your young apple trees thriving during the summer from pomologist John Bunker:

1. Most important, keep a lookout for borers in the trunk of your young apple trees.

Unfortunately in our area, the roundheaded appletree borer (Saperda candida) is the number one enemy of young apple trees.

Photo by Dawn Dailey O'Brien, Cornell University,

The borer beetle lays its eggs under the bark near the base of the tree. The developing larvae tunnel through the wood, eventually weakening the tree until it crumbles and falls over. The trouble sign is small deposits of orange sawdust, called frass, at the base of the tree. Left unchecked, borers usually mean death for your trees.

Borers thrive in shady moist warm environments. Keep grass back at least 6″ from the tree base. Keep a lookout for the frass. Locate the hole or soft spot in the trunk and insert a wire until you locate and kill the larvae. Cut away soft, spongy pockets with a knife. Even serious carving is less harmful to the tree than leaving the larvae alive inside.

After years of experimentation, I think that painting is the best deterrent. I’ve tried a number of recipes and this is my favorite. It’s easy and requires no hard-to-find ingredients. Mix white interior latex paint with joint compound. (The stuff you smear on sheet rock joints and nail holes – you can buy a small tub at any hardware store. Some exterior paint formulations contain ingredients that can harm the underlying phloem.) The consistency should be thick but still quite easy to paint, not glob on. Repaint periodically or each year as needed. This mix will help deter borers. It will also make for easy detection of any infestation you may have. Look for the frass! Using the paint method, you will also need to put some sort of screen or plastic rodent protector around the trunk during the winter months.

We are experimenting with a borer-protection formula using more benign ingredients. It doesn’t last or adhere as well as the paint-joint compound mixture, but it appears to work fairly well.

2 qt quick lime
4 gal milk
1 gal boiled linseed oil

Mix well. Thicken as needed with clay or Surround (available in the Organic Growers Supply section of the Fedco Seeds catalog). Apply with a paint brush. Reapply as needed.

2. Another summer problem could be an assortment of caterpillars. Squish them with your fingers or snip out the branch and burn or dispose of it.

3. Keep weeds away from the trees, ideally at least 9 inches from the trunk.

4. Mulch the ground around the tree with chipped up brush (NOT bark mulch).  Mulch out about 3 or 4 feet from the trunk.

5. Make sure to keep your trees watered in weeks it does not rain much. You want to aim for about 1 inch of water a week.

Have fun and have a wonderful rest of the summer!

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