Pests and Diseases

Fedco Organic Growers Supply carries a complete line of plant protection and pest management products.

Apple Borers
Mice and Voles
Deer
Aphids and ants
Apple Maggots
Scab
Peach Leaf Curl
Plum Curculio
Iris Borers
Lily Leaf Beetle
Companion Plant Combinations for the Garden and Orchard

Apple Borers

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.”

Mice and Voles

Fruit trees and ornamentals are sometimes girdled by mice or voles eating the bark. Girdling will usually kill the tree or shrub. The danger is greatest in winter. Keep the grass mowed in the fall and remove large mulch piles from near the trunks. Rodents like to nest in hay more than in chip mulches. A wrap of window screening or a plastic spiral tree guard will protect your tree from being girdled. If you use screening or plastic spiral tree guards on apple, quince or crabapple trees, remove them from April to October, as they attract borers if left on the tree in the summer. You can leave plastic spiral tree guards on most other trees year-round. MoleMax® Mole & Vole Repellent can also be an effective deterrent.

Our trials show that a mulch of wood chips surrounding young trees greatly reduces the chance of summer vole damage. Tall grasses invite them in. The polyculture model may provide cover for the voles and can result in summer vole damage. Keep the tall perennials back about 12" from the tree. Make your orchard hawk friendly.

Voles Don’t Like Narcissus! For many years we’ve been planting daffodils around the base of some of our apple trees. No particular reason; it just looks great. Come to find out that you can beautify your orchard and deter voles at the same time. Plant daffodils in a circle a foot or two away from the base. The tunneling voles don’t like the bulbs and will veer away.

We don’t have the super-destructive pine voles in our orchard—whether or not the bulbs would deter them, we don’t know. We’re continuing our trials in Massachusetts where the pine voles are a big problem.

Deer

The best deer protection is a collie in the yard. If you don’t have a dog or if your orchard is too far from the house, 7' deer fence will work. Some people have good luck with electric fences. Small protective fence enclosures can be made by circling your tree with a cylinder of chicken wire or other fencing. As a temporary deer deterrent, try Deer Stopper®.

Aphids and ants

Aphids can do a lot of damage to apple trees and they make the young leaves look gross. Whenever you see aphids you will see ants climbing up and down the tree feeding them. Here’s an easy solution. Wrap a piece of stiff paper about 6" wide around the trunk about a foot or two off the ground. Tape this “sleeve” to itself but not to the tree. Smear Tanglefoot® on the paper. Ants will not cross the barrier and, without the ants, the aphids will die. In a day or two no more aphids.

Apple Maggots

The late Don Johnson made nifty apple maggot (Rhagoletis pomonella) traps for many years. We’ve gotten into doing so ourselves. In small orchards, the traps alone may be enough to reduce the pressure to a tolerable level. Here’s how: Cut up plywood (⅜" or ½") into 8" x 11" rectangles. Drill a hole along the top edge. Paint the plywood bright yellow with a 2–3" red spot (the apple) in the center. If you don’t feel like making your own traps, you can purchase Red Ball Traps. In either case, traps are more effective when used with Apple Maggot Lures.

Coat traps with Stiky Stuff and hang 1–6 in each tree in mid-June, positioning the traps at about eye-level with 12–16" of clearance between them and any foliage so insects can get a good look at them. Trim away any foliage that might stick to the trap. Check for AM flies. Scrape the traps off now and then and add new Sticky Stuff when they get too gooky. Remove traps around Labor Day; sticky coating is best cleaned with a solution of Citra Solv diluted in the hottest water you can tolerate.

Scab

Apple Scab (Venturia inaequalis) is the worst fungal disease affecting apples in New England. You can greatly reduce scab pressure by avoiding McIntosh, Cortland, Fameuse and any “Mac” relatives. But this is a tough call since they are all excellent varieties. You can also reduce scab pressure by picking up drops, cleaning up or mowing fallen foliage in the fall, and spreading a thin bit of lime and/or compost (Rainbow Valley or Coast of Maine Quoddy Blend are both good choices) over the fallen foliage in the fall.

To really give your trees a fighting chance against scab using organic products, we recommend the Holistic Orchard Spray program.

There are reports that planting chives around apple trees and using chive infusion as a spray will reduce scab pressure. We’ve been doing so and will give you a report before long. At the very least, we’ll have plenty for our cottage cheese, salads and baked potatoes.

Chive Infusion Spray Recipe: Pour 1 quart boiling water over 1 cup chopped chives. Cover and set aside to cool. Strain and use the liquid within 4 hours.

Peach Leaf Curl

Peaches are usually unaffected by pests or diseases in northern areas, the occasional exception being peach leaf curl (Taphrina deformans). PLC is not a fatal problem but does need to be controlled if you get hit with it. Look for crinkled or puckered foliage in spring. Remove affected leaves and compost them. Spray the tree early the following spring while it is still dormant (before any buds open!) with lime sulfur or copper. Onion, garlic or horsetail spray while leafed-out may also be effective.

Plum Curculio

Plum curculio (Conotrachelus nenuphar) is a terrible plum and apple pest. Many organic growers spray Surround clay powder on their trees to combat this weevil. Many years ago we planted garlic near one of our apple trees and neglected to harvest all the bulbs. Now we have a small colony of garlic plants around the tree. Recent reports are touting garlic as a curculio deterrent. Anecdotal evidence suggests the garlic may be working at our place. Plant more garlic!

Iris Borers

The key to preventing iris borers Macronoctua onusta is to peel off the dead foliage down to the rhizome in early spring. Destruction of last season’s dead foliage destroys overwintered eggs harbored in plant residues. Once the new leaves emerge, inspect them for signs of iris borer larvae. Classic signs of the presence of iris borer larvae is dark streaks, water-soaked areas and ragged foliage. If you find evidence of larvae, gently press your hands together on each side of the base of the leaf, then carefully run your hands up the leaf stalks to squish any larvae that may be inside.

If you find an active infestation in your existing iris beds, dig up the rhizomes after they have flowered, trim off the foliage, inspect the rhizome and cut out any borers and rotten spots. Replant the rhizomes immediately and enjoy the results the following spring!

Lily Leaf Beetle

It takes less than 10 minutes a day to have gorgeous organic lilies. Each day during the first part of the growing season inspect the lily foliage and pick off the first flush of adult beetles and squish them or drop them into soapy water. You can’t miss them—they look like gorgeous bright red jewels. Also look for dull orange eggs on the undersides of the leaves. Smash them, too! If you do this faithfully early in the growing season, you’ll give your lilies a chance to grow big enough to withstand the relatively minor nibbling from the few rogue beetles you missed.

Beetles will often drop to the ground as you reach for them and disappear into the soil. If you lay black mulch fabric down when you plant your lilies, the beetles will land on it and then there will be no escaping your deadly grasp! If you’d rather not smash bugs with your morning tea, try mixing a 1:8 dilution of Dr. Bronner’s Peppermint Soap with water. Spray the plants and be sure to get the underside of the leaves. Many Fedco customers have reported success with this method, and I have found success when combined with quick & daily vigilance.

Companion Plant Combinations for the Garden and Orchard

Generations of gardeners have identified certain plants as beneficial to each other in the garden. We can gather insight into what is possible when we step back a moment and observe the work of nature. Many old garden books contain some version of the following:

Apples planted with chives, garlic, tansy, horseradish and nasturtiums will have less scab and woolly aphids.
Asparagus likes tomatoes, calendula, basil and parsley, which deter asparagus beetles.
Strawberries grow better near lettuce, borage, and spinach. Spinach roots secrete saponins, which are antifungal and antimicrobial, and borage breaks down into calcium, potassium and other minerals.
Roses like garlic and chives, which can help with blackspot, mildew and aphids. Geraniums repel Japanese Beetles.
Grapes grow well with hyssop, which increases fruit yields.