In many parts of central and northern New England the roundheaded appletree borer,
Saperda candida, is
the number one enemy of young
apple,
crabapple and
quince trees. If you are growing young apple trees in these locations, you must protect your trees from this pest. Farther south and north the borer may not be a pest. If you don’t know if they are a problem in your area, check with any grower near you: they’ll know. Otherwise, err on the side of caution. The borer does not endanger other fruit trees or ornamentals.
Borer beetles lay eggs under the bark near the base of the tree. The developing larvae tunnel through the wood, eventually weakening the tree until it falls over. The trouble sign is small deposits of orange sawdust, called frass, at the base of the tree. Check lower trunks for frass and tunneling in late May, and again in September. Left unchecked, borers usually mean death for young trees.
Here are five strategies for controlling borers:
Paint the trunks: Painting is likely 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 as needed. This mix will help deter borers and also make detection of infestations easier. Look for the frass!
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. Apply with a paint brush. Reapply as needed.
Cut It Out Once you’ve identified a hole or soft spot in the trunk, insert a wire and dig around until you locate and kill the larva. Cut away soft spongy pockets with a knife. Even serious carving is less harmful to the tree than leaving the larvae alive inside.
Blasted Borers: When you discover a soft spot or hole in the tree, get yourself a can of compressed air (for cleaning computers). Put the long skinny tube nozzle up to the hole and give it a blast. Should do the trick.
The Polyculture Deterrent: Borer beetles thrive in shady moist warm environments. Keep grass back at least 6" from the tree base. Trials in our “functional” orchard suggest that a mixed polyculture environment may disguise the apple trees and fool the borers. We plant woody and herbaceous perennials around the trees, keeping them back 12" or so. Borers are lazy opportunists. If there are a lot of apple trees within easy reach, they will attack. Otherwise, you may never see them. The polyculture orchard may present too much work for them.
Neem Oil: News Flash: Neem Naturally Neutralizes the Northeast’s Nasty Nefarious Nemesis!
In many parts of central and northern New England, the roundheaded
apple tree borer (
Saperda candida) is the #1 enemy of young apple, crabapple and quince trees. The larvae tunnel throughout the wood of the trunk—usually just below or just above the soil or mulch line—weakening the trunk to the point of breakage. Left unchecked, borers usually mean death for young apple trees. We’re grateful that Michael Phillips has identified an effective, organic, nontoxic and easy defense for plantings large and small:
pure neem oil, sprayed as a trunk and soil drench at 1–2% concentration. For optimal results, spray this “neem drench” 4 times a year: early spring, late June, late July and fall.
To prepare a 4-gallon batch of the 1–2% neem oil drench: Combine 5-10 fl oz
warmed neem oil with 2-4 teaspoons biodegradable dish soap. Stir vigorously to emulsify—it should become milky. Add warm water until you reach the 4-gal mark, then stir again.
Optional: Stir 2# of
Surround® WP into the mixture. This will give your trunks a whitish hue, making it easier to spot the rust-colored frass that indicates presence of borer larvae.
Apply the spray generously, making sure to completely drench the trunk up to the the first branch (but not the branch itself), as well as the soil at the base of the trunk. Be especially generous when spraying around the base of the trunk: spray enough so that it pools and then slowly soaks in (borer larvae often dwell in the tree just below the soil surface).
CAUTION: Do not apply this 1–2% neem spray to leaves—it could damage them. Be sure to clean sprayer tank and flush line after use.
Please note that although this neem drench is a powerful tool in the battle against borers, we still recommend getting on your hands and knees to inspect your young apple trees for frass and tunnels at least once a year. If you notice evidence of borer activity, locate the hole or soft spot in the trunk and dig out the larva with a wire. Cut away soft spongy pockets with a sharp knife. Even serious carving is less harmful to the tree than leaving any larvae alive inside.
Michael Phillips now recommends that when you’re on borer duty, bring along a butter knife and a container of solidified neem oil (thick as butter at 60°). If you find borer damage and cut away the affected tissue with a sharp knife, slather on the neem oil to fill the cavity. According to Phillips, “bark tissues and pores in the wood will carry azadirachtins to the borer (if indeed missed), and arrest its further development…the fats in the neem will hasten callusing of the wound.” If the site of this surgery is near the soil line, cover it up with soil, and “know you’ve done everything possible to deter this curse.”
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