Pests and Diseases

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

Apple Borers
Scab
Apple Maggots
Mice and Voles
Caterpillars
Deer
Aphids and ants
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 an issue. 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. Borers also feed on other members of the rose family, such as pear, hawthorn, Aronia and Amelanchier.

Borer beetles lay eggs under the bark near the base of the tree. The developing larvae tunnel through the wood, weakening the tree until it eventually 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 our strategies for controlling borers:

Coat the trunks with Neem Oil: We have been experimenting with several methods for treating borers using neem oil. It’s easy and effective. All you need is a paintbrush and undiluted neem oil warmed to liquefy. Paint neem on young tree trunks from the soil line up 12". We apply one time only around July 1. If applied in May or early June, the neem dries and becomes ineffective.
Note: We have noticed that the adventitious root bumps of M111 show some sensitivity to undiluted neem. We’re having good results spraying a 2% neem solution on the trunks of M111 and other clonal rootstocks.
Coat the trunks with paint: After neem oil, paint is likely the best deterrent. It’s easy and requires no hard-to-find ingredients. Do not apply paint until trees have been in the ground for 3–5 years. Until then, be sure to continue monitoring them for signs of borer.
Recipe: 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. Make sure to use interior paint, as some exterior paint formulations contain ingredients that can harm the tree's 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. Once you locate a borer hole, you’ll have to cut or blast it out (see below). Look for the orange frass!
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. We’ve found that a little neem oil brushed on the wound after borer hunting can prevent further infestation or fungal growth, and may even speed up the development of callus tissue.
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.

Scab in the Apple Orchard

Apple scab (Venturia unaequalis) may be the most challenging disease for the New England apple grower. Scab is a fungus, spread by spores that overwinter in fallen fruit and leaf litter, rising up in rainy spring weather to cause grief all over again. It appears as small rough black patches on the fruit or foliage. A bit of scab is not a bad thing. It won’t hurt you or your tree or fruit. Some growers actually believe that a small amount of scab triggers a beneficial self-protection response in the apple. But a lot of scab can destroy the fruit and even kill the tree. Severity of infection can vary depending on the year, the site, and the variety.

With organic or conventional fungicides as a last resort, what can you do to avoid or minimize scab damage in your trees?

Avoid susceptible varieties. Although nearly all apples are susceptible to some extent, certain varieties are especially vulnerable to scab. In particular, McIntosh and its relatives are scab magnets. These include Cortland, Fameuse and Macoun. If you grow these, you’ll probably struggle with scab in your orchard. If you can avoid these varieties, you may be able to keep scab to a tolerable level without spraying fungicides. Most heirlooms can be susceptible but should be quite tolerant as long as the more highly susceptible varieties are kept away.
In 1945, Purdue, Rutgers and the University of Illinois began a collaboration to develop scab-immune varieties. Many of these have PRI in their names. (Prima, Pristine, Williams Pride, etc.) They bred the varieties using Malus floribunda as a parent. It contains a gene that imparts scab immunity to the fruit. By crossing and recrossing, they were able to isolate and include this gene in the final introduction. We’ve offered some of these varieties, including GoldRush from the PRI program, and Liberty from the associated New York breeding program. If you like the fruit from these varieties, growing them can be a good strategy for avoiding scab.
Thin the fruit. In late spring or early summer, we thin all our tree fruit, removing enough fruitlets that the mature fruits won’t touch. You want air circulation. Insects also like those places where fruits rub against each other.
Clean up drops and fallen leaves. Scab lives in the fallen fruit, as do insects. Eat the drops, make them into cider, feed them to your livestock or compost them—just don’t leave them at the base of your trees. Some farmers let livestock in the orchard to eat the drops. Also rake up leaves in the fall. Burn, compost or mow them. By practicing good hygiene in the orchard, some growers have been able to grow good McIntosh and other disease-prone varieties organically.

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.

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. Stomp around the trunks after each fresh snowfall to create a packed-ice barrier that will prevent mice from traveling beneath the snow. 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 wood chip mulches. A wrap of hardware cloth or a plastic spiral tree guard can protect your tree from being girdled.

If you use screening or plastic spiral tree guards on apple, quince or crabapple trees, be sure to remove them from April to October, as they attract borers if left on the tree in the summer.

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. So keep the tall perennials back about 12" from the tree.

Also, 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.

Deer

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

Caterpillars

Most caterpillars will not damage healthy plants and are important members of the environment. However, a few kinds, such as tent caterpillars and browntail moth caterpillars, are extremely destructive to fruit trees. You’ll know when you see them—they hatch in large crowds and rapidly defoliate plants. Vigilant daily observation, manual collection and disposal are necessary from mid-summer to fall. Be careful handling browntail nests. They can cause a severe rash.

Aphids and Ants

Aphids can do a lot of damage to apple trees and they make the young leaves look gross. Often when 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.

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 are 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 and 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.

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