Some things to consider when planting apples:
- Ease of growth- Apples are among the easiest fruit to grow in our climate, but do need some basic disease and pest management.
- Drainage- Dig a 16”-deep hole where you want to plant, preferably in the winter. If water fills the hole and stands in the hole more than 36 hours, you will need to mound up the planting site. You want to build a 3′-5′ wide mound with 16” to the water level.
- Sunlight– Apples trees need ¾ of a day (6-8 hours) of good sunlight. If your site is shady before 4 pm in mid-summer, it is probably too shady to produce good fruit.
Apple trees are grafted trees. This means wood of the apple variety is grafted onto apple rootstock. What do rootstocks do?
- Rootstock helps determine mature tree size, when trees are grown and managed to their full potential bearing size.
- How much room do you have? Trees on smaller rootstocks take less room, but might not bear as much per tree as larger rootstock trees.
- How high on a ladder do you want to climb? For a semi-dwarf apple you will want a 10′-12′ ladder in order to prune, thin, and harvest the tree.
- Tree Spacing– Remember there are size options because of rootstocks. Larger trees need wider spacing, smaller trees can be closer together as they have a smaller root system and compete less with neighboring trees for water and nutrients.
- Apple trees are grafted: a select variety onto a selected rootstock.
- In general, smaller rootstocks fruit earlier than larger rootstocks, usually 1-2 years earlier for first fruit.
- In general, smaller rootstocks need staking or trellis support – their smaller root systems might not support their fruit load.
- Smaller rootstocks can be on closer spacing and yield more fruit per square foot than larger rootstocks, but require support.
- Larger rootstocks are more tolerant of marginal soil and slightly more drought tolerant when established
- Larger rootstocks can grow into ‘deer resistant’ trees. Protect with fencing when young, and train so most scaffolds reach above deer nose level. Deer will still browse lower branches and fruit, but not cause permanent damage.
Pollination– what does that mean? All fruit trees need to have pollen moved to the anthers of their flowers by a pollinating insect for that flower to become a fruit.
- Almost all apple varieties are self-sterile. Self-sterile or self-infertile means that another apple tree of a different cultivar or variety is needed to set fruit (cross-pollinate).
- Some apple varieties are triploid crosses, and do not provide viable pollen to other apple trees. These include some popular varieties including Gravenstein, Jonagold, and Karmijn de Sonneville.
- In our climate, apple bloom times can extend over a long period. Matching varieties with overlapping bloom is crucial to fruit set.
Apple Bloom Times
Choose your pollinizer from the same or adjacent columns. For example, Idared pollinizes Williams Pride (same column) or Akane (adjacent column), but not Elstar. Varieties marked with an asterisk* do not work as pollinizers for other varieties (triploid crosses with sterile pollen).
|Beni Shogun Fuji
Harry Masters Jersey
Reines des Pommes
What to look for in purchasing a tree?
- Bud union of the graft where the variety of apple is joined to the rootstock should be firm and clean. This is usually noticeable as a bump or crook near the base of the trunk. Below the crook is rootstock and above the crook is the wood of the apple variety.
- Tree is tagged with variety and rootstock.
- Will you need to permanently stake or support this tree? (apples grafted on dwarf and mini-dwarf rootstocks need support)
Planting Requirements: Are you ready to take care of your trees? If you’re bringing home bare-root trees, you want to be able to plant right away.
- You can plant if your soil isn’t too wet to work and you can dig holes directly.
- Mound the soil if needed to keep roots above the winter high water table.
- For bare-root trees:
- Planting: when planting, be sure to keep the graft union 2″-4″ above soil line;
- Root care: prune off broken roots, spread out over soil mound built in the bottom of the hole.
- For potted trees:
- Water the pot so the soil in the pot is moist;
- Remove the pot and use your fingers or a garden claw to rough up the roots (during the dormant season, you can wash some of the potting soil off the roots before planting);
- Plant the tree the same depth it was in the pot. Be sure not to bury the graft!
- For both bare-root or potted trees:
- Water trees in to settle the soil after planting;
- Have a plan for watering during the summer:
- Young trees need consistent summer soil moisture during their establishment;
- During the summer, check the soil often to make sure it is moist to a depth of 6”-8”;
- How do you check? 24 hours after watering, dig a 6″-8″ deep hole near the tree and check for dampness. If the soil is not moist to that depth, you did not water enough.
- Plan to stake your trees at planting – even semi-dwarf trees need staking the first year. We live in a windy area. New trees do not yet have big enough root systems to stand up to strong winds. Dwarf and mini-dwarf trees should be planted with a permanent stake or trellis support. Use a round stake and stretchable material for tying to minimize bark damage.
Fertilizer and lime (for more detail see nutrition section below)
- Young fruit trees benefit from fertilizer the first 3 years to stimulate growth. Use a fertilizer formulated for fruit trees for best results. In sandy or gravelly soils, they may need fertilizer past 3 years.
- Western WA soils are typically acidic, and fruit trees prefer a neutral pH (6.0-7.5). If the soil pH is below 6.0, your tree may not be able to utilize nutrients that are present. Liming at planting and annually in the fall will help sweeten the soil (raise the pH) and provide calcium for good fruit.
Year 1 Post Planting
- Keep soil moist, keep weed free area, 3’-4’ diameter. Those weeds compete for moisture! They also provide cover for field mice, who will nibble bark and roots and can stunt or potentially kill young trees.
- Insects and disease – Watch for mildew, scab, leaf rollers, aphids, apple midge. Most diseases aren’t hard to manage in the first 2 years (see Disease and Pest Management section)
- If new growth shoots (terminal shoots) stop growing by early summer, it is one of three things usually: not enough water, mildew (gray, dead looking tips on branch ends), or deficient nutrients. Lime and compost additions in years 1 and 2 can help.
- Remove all but 2-4 fruits first year. This helps put the tree’s energy into growing wood and roots.
- Prune apples (section below) in dormant season (before leaves come out).
- New growth – If growth per shoot is less than 18” per year on average, then the tree might be lacking water and/or nutrients.
- Keep 3′-4′ area weed-free around trees during the first 7-8 years so voles/field mice don’t eat your tree’s roots, and there is less competition for moisture.
- Water – Trees will need 1” of water per week in the growing season in average soil, either from rainfall or irrigation. Heavier soils may need less water, sandy soils more water.
- Check the soil moisture level to make sure you are watering enough: 24 hours after watering, dig 6”-8” down and make sure soil is moist.
- Train new shoots in late summer (details in the pruning principles section).
- Fruit – Leave up to 6 fruits close to the trunk, remove all at ends of branches. How do you know if you’ve left too much fruit?
- Tree does not grow 12”-18” per shoot;
- Fruit stays small;
- Branches bend or break under fruit weight.
To understand the needs of fruit trees, it is necessary to understand our climate patterns and our soils in Western Washington. The maritime Pacific Northwest is known for being rainy, but most of our rain falls between October and June. Our summers are typically dry. Our soils also tend to be high in organic matter. High organic matter combined with a rainy environment can cause our local soils to be acidic, with pH ranges below 6.0. Have your soil tested to determine both pH and nutrient availability. If you are planting your trees into imported (manufactured) soil, ask the company if they have a soil test that will provide you information on pH and nutrient values of the mix.
Ideally, a range of 6.0 to 7.5 is optimal for orchards. In general, the availability of micronutrients is lower in alkaline (high pH) soils. Nutrients such as iron and zinc may not be in a form available to plants. In contrast, phosphorus may become limiting in acid soils. Also, in acid soils, aluminum can become available, which is not a nutrient and is toxic to plants in high concentrations. At pH 6 and higher, very little aluminum is in solution.
Additionally, soil pH affects the abundance of microorganisms. Bacteria are generally more prevalent in alkaline soils and fungi dominate in acidic soils. This is important because microbes are responsible for the cycling of nutrients. The most diverse and numerous populations are found in near-neutral soils. Furthermore, soil pH influences pathogenic microbes, and growers can adjust pH to manage some plant diseases.
Low pH soils (5 and lower) can result in:
- Calcium (Ca) and magnesium (Mg) deficiencies;
- Restricted root growth or regeneration due to aluminum (Al) toxicity;
- Reduced availability of Phosphorus (P);
- Reduced efficiency of Nitrogen (N) and Potassium (K) use and poor response to N and K fertilizers.
Acidic soils may be neutralized over time with the application of lime. The amount of lime needed to bring the pH to nearly neutral is dependent upon the buffering capacity of the soil and how much the pH needs to be adjusted. The higher the amount of clay and organic matter, the higher the buffering capacity and more lime needed. There are many sources of lime available. Dolomite lime also contains magnesium as well as calcium but is slower acting than agricultural lime (calcium carbonate). This all sounds complicated, but the take away message is that annually applying lime to your orchard in the fall will help your fruit trees thrive.
Young trees (first 3 years) can benefit from added fertilizers (unless your soil tests high in nutrients). Nitrogen (N) stimulates vegetative growth, but too much can lead to excessive, weak growth. Phosphorus (P) encourages root growth. Potassium (K) helps flower buds form, and in bearing trees can help produce higher quality fruit.
Use a fertilizer formulated for woody plants or fruit trees. Conventional fertilizers for fruit trees usually have a formulation with lower nitrogen and higher phosphorus and potassium ratios. For many years, we have had a local farm company blend a conventional fertilizer formulated for local soils, with NPK values of 8-18-18. This fertilizer also have micronutrients incorporated (zinc, boron, manganese). There are other good fertilizers out there, including organic fertilizers. There is a chicken manure fertilizer, Nutri-rich 4-3-2, that has added calcium, and has proven locally to be a good all-purpose fertilizer for both young fruit trees and vegetable gardens.
Apply conventional fertilizers in spring just as new growth starts, usually mid-March. A second application can happen in late May, and a third in early July (the ‘holiday’ method of remembering: fertilize on St. Patrick’s Day, Memorial Day, and 4th of July). Organic fertilizers break down more slowly than conventional ones, so one application in early March followed by one in early June is usually adequate. Follow the directions on the package to calculate how much to apply. When in doubt, always apply less than you think you need rather than more – you can damage your tree by applying too much!
Young fruit trees cannot tolerate drought. Even established trees need summer moisture to produce quality fruit. Because we cannot count on summer rain, growing fruit trees means watering. How much should you water? There is no easy answer, as it will depend on your soil. Sandy soil will hold less water than silt or clay rich soils, so may need more frequent watering. Moisture retentive soils high in clay will need less frequent watering in general.
Techical Alert! An interesting tool to explore is the Web Soil Survey. This online tool maps soils and provides data about those soils. You can enter your address and find out about your native soils, including the water storage capacity of the soil (in the top 60 inches of soil). This is a measurement of how much plant-available water the soil can store between soaking rainfalls. For instance, just north of Bellingham is an area of silt loams, including the Whatcom-LaBounty silt loams and Yelm silt loams. These soils have a water storage capacity of 12.7-16 inches (when the soil depth is 60 inches or more). These soils theoretically can provide plants growing in them up to 16 inches of water during dry periods (in reality, not all of that water is available). If you use the ‘plants need 1 inch of water per week’ rule of thumb, the Yelm silt loam theoretically has a potential of unirrigated plant support for 12-16 weeks. In contrast, part of the main Cloud Mountain farm is made up of Kline sandy-gravelly loam, with a water storage capacity of 3.4 inches. This soil is planted in fruit trees, and needs irrigation in summer to thrive.
So, how can you tell if your soil has enough moisture beyond the theoretical? If it has been dry for a week or more, dig a hole to check soil moisture. The soil around your fruit trees should be damp to a depth of 6”-8”. If you’ve recently watered, wait 24 hours, then dig the test hole. If you soil is not damp, you didn’t water enough. After a few times, you should begin to get a sense of how much you need to water to get that soil damp to that depth.
Pruning Apples: Central Leader and Open Center Form
Pruning refers to cutting wood, training refers to pulling or bending wood into a desirable position. Why prune and train your fruit trees?
- To shape and balance your tree’s form;
- To open the tree to light and air circulation;
- To improve fruit quality;
- To control vigor.
Stake all your fruit trees. Use posts that will be at least 5′-6′ tall at finished grade. We live in a windy place; the stake not only should be used to hold the tree up but more importantly it can be used to hold the fruit up. The varieties we sell often begin bearing fruit in the trees’ second year. You may have the fortune of being the recipient of 10-15 lbs of fruit in the second year, but if your tree isn’t staked, it will probably be destroyed by the weight of the fruit even before the wind has a chance. A round stake, 6″ away from the trunk, installed at planting is the ideal. In addition to the treated stakes we sell (raspberry stakes), round metal pipe also works well. Metal fence posts (T-stakes) have edges that can damage your young tree’s bark and flanges that can damage roots if installed after planting. If using a T-stake, install before planting, then wrap the stake in a non-moisture holding material such as closed cell pipe insulation.
Use your tree stake as a training tool. Tie the trunk of the tree to the stake just below the first branches. Tie the leader to the stake every 18″-2′. For all tree tying, we recommend using an expandable material that won’t cut into the tree as it grows. Stretch Tie is a commercial orchard product designed for this purpose, available at the nursery.
Pruning: General Rules
Pruning is a requirement for success. Fruit trees were bred over many decades to bear on young wood. In apples, the most productive wood is 2-5 years old. Pruning not only shapes the tree, but also determines the quality and quantity of fruit.
- Utilize training into your pruning program for the best success;
- If you prune into one-year-old wood you will delay fruiting of that branch, meaning that wood will continue to produce vegetative buds but not flower buds;
- If you prune into one-year-old wood, the net effect will be to make more one-year wood;
- If your goal is to produce fruit, don’t prune into one-year-old wood after the planting year;
- Unpruned one-year-old wood will develop many flower buds in its second year;
- Pruned or headed one-year-old wood will develop almost no flower buds in its second year.
It is important to let the one-year wood grow into two-year-old wood. Does that mean letting the young branch you think you should shorten get too long? In some cases, yes. In the second winter you can cut the branch back to the desired length. Make sure when you prune, you are cutting into the two-year old wood. Pruning does decrease your tree’s fruiting potential by removing wood from the tree, but is necessary for fruiting success.
Limb spacing (branch placement) on semi-dwarf trees (the importance of branch placement is discussed below):
- Bottom set of branches should be about 26″-36″ above the ground;
- Lowest set of branches should have 24″ min and 36″ preferred before you start your second set of branches;
- All other sets of branches only need 2 feet between them.
Limb spacing (branch placement) on mini-dwarf trees:
- Bottom branches should start at 24″. All other sets of branches should be about 12″-16″ between them.
Controlling branch vigor:
- Branch vigor refers to how strongly a branch is growing. Three major factors control branch vigor and flower bud formation: branch placement, branch angle, and caliper. These three things interact to balance and counterbalance growth within the tree.
- Branch placement (elevation) in tree. The lower the branch in the tree, the less vigor the branch has. The top of the tree will always be the strongest growing part of the tree (this is called apical dominance).
- Branch Angle. The more upright the branch, the more vigorously the branch will grow. If you take a vigorous branch and pull it down (training bands are available at the farm) to a horizontal position, you can nearly stop all of the growth in that branch.
- Caliper (thickness of branch). When comparing two branches in a tree, if the branches are the same elevation and growing at the same angle, the thicker branch will be more vigorous. This is why it is important to maintain older branches in the bottom of the tree.
You can control branch vigor by manipulating these factors:
- Branch angle is the easiest way to manipulate branch vigor. By pulling upright branches more toward horizontal, you can decrease vigor. Experiment with branch angle to manage your fruit trees’ vigor. Ideal branch angle for fruit bud production should be between 60 and 90 degrees (90° is horizontal).
- Branch caliper plays a key role in the vigor equation. Think of branch thickness as the width of a road. The wider the road, the more cars you can get down the road, or in this case energy (growth) through the branch. In an ideally shaped central leader tree, the lowest branches will be the thickest, and the topmost branches will be pruned and trained to reduce vigorous growth and encourage short, less vigorous, productive branches.
Prune your tree at planting (when planting bare root)
Why? Fruit trees that are bare root have had most of the tiny feeder roots cut off during the digging process. If the leaf surface is not reduced via pruning during the dormant season, the tree will become moisture stressed when the tree begins to leaf out. The tree may take 6 to 10 weeks to regenerate feeder roots. If you don’t prune your tree, then the leaf surface will overtax the tree’s ability to draw water up from the roots.
Central leader tree form
This is one of the easiest forms to train dwarf and mini-dwarf apple trees. A central leader tree form is similar in shape to that of a Christmas tree. The bottom branches stick out farther from the trunk than those at the top of the tree. The suggestions listed below apply directly to this tree form, however, the concepts can be used with any pruning training system. The slender spindle form to the left is one type of central leader tree training that uses bending rather than pruning to promote fruiting wood.
- Choose 3 to 5 branches that radiate from the trunk and are evenly spaced around the tree. These branches should be as close to the same thickness at the base as possible. (Remember that the greater the diameter of a branch the faster the branch will grow.) Branches that are growing in a horizontal habit tend to be more fruitful than upright branches. Next prune all of these branches to 18″-24″; if the branches are only that long or slightly shorter then no pruning will be required.
- Pruning the leader at planting- First you must select one upright shoot to become the leader. It doesn’t have to be the straightest shoot nor the strongest shoot; in fact, we tend to choose a shoot that is closest to the caliper of the side branches. Prune off all other upright shoots. Then prune the future leader to 8″-10″ above the highest branch on the tree.
Pruning the tree’s central leader: year 2 and up
On the leader, make a pruning cut, leaving a side shoot of one-year-old wood unpruned. This means the side shoot can’t be too long; 4″- 15″ is ideal. On older trees, this is the preferred cut to use to manage the leader.
Open-center tree form
We can apply the same pruning principles to open-center trained trees. This training system is often used for semi-dwarf and semi-standard trees where a central leader tree would grow too tall to manage. Open-center trained apples have multiple leaders, spreading out the trees’ energy. An open center apple should have 3-5 evenly spaced leaders. Each leader should be similar in vigor. If one leader is too vigorous, the tree will become unbalanced. The vigorous leader can be pulled a little flatter to decrease vigor, or a less vigorous leader can be pulled more upright to increase vigor.
Prune at planting, choosing 3-5 evenly spaced branches (if the tree has branches) to form the leaders. If you are planting an unbranched whip, cut the tree back just above where you want your leaders to form. The branches should ideally be at a 45-60° angle (90° is horizontal). If the leaders are flatter than this, the weight of the fruit is more likely to break them.
Like in central leader trees, large caliper branches that develop high in the canopy of an open center tree must be removed. Each leader needs to have the thick branches low down, with thinner branches higher up. Branches and spurs are thinned to keep all the fruit buds open to light. The principles of branch angle, caliper, and placement seen in training central leader trees apply, but you are working with multiple leaders instead of just one.
When working with open-center trees, one more aspect must be maintained; all the leaders must be close to the same height. If one leader grows too much taller than the other leaders, it will gain apical dominance and grow out of balance. To help balance the vigor in the leaders, sometimes you will pull down/flatten vigorous ones, and pull up weaker ones. This position training usually takes affect quickly, within a year.
Espalier or Fruiting Wall Training
Training fruit trees to a flat fence or trellis is known as espalier (es-PAL-yay). Espalier training can create an art form for your garden and give you productive fruit trees in a small space. The shape you train your trees to can take many forms. Some forms are very formal, but even the trellis systems used in commercial orchards could be considered a form of espalier. Apples on dwarfing rootstocks such as M-27 and G-41 are the easiest fruit trees to espalier. They produce long-lived fruit spurs, reducing the amount of renewal pruning and retraining necessary.
To train apples to a form, or fruiting wall, plan in advance the form you choose to use. This will help you decide tree spacing. It is easiest to install your trellis system and training framework before planting your trees. For getting started, bare-root, lightly branched trees give you the most flexibility in starting the training.
Other orchard management tasks should also be on your radar. Once your apple blossoms have been pollinated, the fruit will begin to form. Can you let your trees keep every apple set? Short answer: NO. One way to think about managing fruit load is that quantity and quality are related. If the tree has too much fruit on it, several things will happen:
- The fruit will be smaller;
- The fruit might not ripen as well, with lower sugars;
- The tree might begin to fruit biennally – in other words, you will have a heavy crop one year, and the following year almost no fruit.
One solution is to thin the fruit as the apples start to grow, either just after bloom or in the next few weeks. Some fruit will naturally drop (the “June drop”), but often there will be 3 or more apples remaining on each fruiting spur. Removing some of those fruits allow the remaining fruit to size up. Thinning can also reduce the weight of the fruit on the branches. It can prevent codling moth larvae from moving between fruits. While thinning is also a good time to put maggot barriers on if you use them.
Another method of pruning is to flower thin your trees at or near full bloom. This method is especially effective for varieties that have strong tendencies toward biennial (every other year) bearing. This method works especially well for Honeycrisp, Gravenstein, and most hard cider varieties as they tend to have heavy and light years of fruiting. To flower thin, use scissors or small pruners to clip through the stems of blossom clusters. Cutting right below the flowers is optimal. Removing every other flower cluster, especially those on the top of the branches helps ensure return bloom the following year.
Fruit Load Support
As the apples grow through the summer, they become heavy loads for the tree to bear. Sometimes the fruit is heavy enough to break branches. During late summer or early fall when the fruit is close to maturity, a windy day can destroy a tree. Be proactive and help the tree support that fruit load. This is especially crucial for young trees and for trees on smaller rootstocks. There are several methods of fruit-load support that work.
- Propping branches. For open-center/multiple leader trees, one of the easiest ways to support fruit load is to prop up the limbs. Strong stakes can be tied with soft material to the limb, then lifted slightly so the weight of the fruit rests on the stake rather than loading the branch. In central Washington, before trellis system orchards became popular, long stakes of pine were notched on one end. The notch was placed below the branch, then lifted so the weight was propped on the stake.
- Trellis support. Trees grown on a trellis system use strings tied to center stakes or to the wires of the trellis to support fruit load.
- Staked Maypole system. Freestanding trees grown on a stake can have strings or wires tied to the stake to support limbs.
Basic Disease and Pest Management:
Apple trees have been grown in home orchards for centuries. The goal of many gardeners today is to have fresh fruit from their own trees with a minimum of spraying. There are many ways to reach that goal, but young trees do need some annual spraying to be healthy and productive. We try to emphasize organic and least toxic methods for keeping your orchard healthy.
Choose disease resistant fruit tree varieties when possible.
- Monitoring your orchard for flower bud and blossom stages is the key to good dormant spray timing.
- Monitoring your orchard for problems is key to good pest management.
- Know why you are spraying! Some sprays recommended here are proactive – trying to prevent common problems through maintenance. Beyond general maintenance (dormant) spraying, never spray without identifying the problem.
- When mixing spray solutions, always mix less than you think you will need, as disposal of the leftovers is difficult. Try spraying just water on your orchard to see how much will give you good coverage.
- Always follow the directions on the container label. If the label is missing or unreadable, contact the company for directions (most pesticide labels are available online).
- Many insect pests have natural controls in the form of beneficial insects. Avoid using broad-spectrum insecticides if possible. If they are necessary, spray at dusk or dawn to limit the impact on bees and other beneficial insects.
- Apply dormant oil, being sure to thoroughly coat the branches and trunk bark, to help control codling moth.
- Between flower bud stages 4-6 apply a delayed dormant spray of micronized sulfur and oil plus Bt (Bacillus thuringiensis). This spray helps protect the trees against powdery mildew infections and smothers eggs and crawlers of aphids, mites, leafrollers, and scale.
- Between flower bud stages 6-7 (pink and first bloom) apply a spray of micronized sulfur to prevent scab and powdery mildew. There is research that seems to indicate that adding potassium bicarbonate (Kaligreen, Milstop, BiCarb Old Fashioned Fungicide are all brands of this) to this sulfur spray increases protection for scab and mildew. This spray is not necessary for varieties resistant to these diseases. Bacillus thuringiensis (Bt.) also can added to this spray to help control leafroller. Bt. can also be applied separately or mixed with insecticidal soap to control leafrollers and cutworm at this stage.
- At petal fall apply a second scab and mildew spray, using sulfur with a spreader- sticker. Bacillus thuringiensis (Bt.) or spinosad can be added to this spray to help control leafroller. Bt. or spinosad can also be applied separately or mixed with insecticidal soap to control leafrollers and cutworms at this stage.
- Monitor for aphids and leafrollers.
- Use online models to time controls for codling moth and apple maggot, or put maggot barriers on developing fruit when thinning.
- Monitor the developing fruit for problems. Remove damaged fruit from the tree, and any fallen fruit and destroy (do not compost unless you have a very hot compost system).
- Rake up and destroy fallen leaves and fruit. If codling moth or apple maggot has been a problem, do not compost but discard the fruit in the garbage.
- Prune your trees to keep them open to light and air circulation.
- Keep the orchard clean, removing diseased wood, foliage, or fruit if needed. Rake up fallen leaves in the fall, or mow them so they decay quickly.
- Keep the trees adequately watered in summer. Stressed trees are more prone to problems.
- Encourage your neighbors to keep their fruit trees healthy, too. Pests don’t recognize property boundaries!
Fungal Diseases of Apples
- Powdery Mildew is a fungal disease, Podosphaera leucotricha, that infects both the leaves and fruit. Repeated infections can cause ‘blind wood’ or wood with no fruit buds. The fungus overwinters in leaf buds.
- Powdery mildew infections are most common in warm springs. The temperature range of 66°F-71°F is optimal for infections to occur.
- Powdery mildew can be controlled by spraying at pre-pink (stage 4). If you miss this preemptive control, you may need to remove infected wood and spray again.
- Some organic sprays that can help prevent mildew infections include micronized or wettable sulfur (pre-pink), neem oil, and Kaligreen, Milstop or Bicarb Fungicide (potassium bicarbonate). Some research has shown that combining wettable/micronized sulfur with potassium bicarbonate can improve control of both powdery mildew and scab.
Scab is a fungal disease of apples caused by the ascomycete fungus Venturia inaequalis. The disease manifests as dull black or grey-brown lesions on the surface of tree leaves, buds, or fruits. Scab infections occur in the spring during wet weather. The infections are a function of both leaf wetness and temperature. You can see from the chart that in colder springs when daytime temperatures are in the 40’s, it can take 20-40 hours for infection to occur. The warmer the days are, the shorter time for infection to occur. Why is it so important to control this disease? Scab infections on fruit are mostly cosmetic, but leaf infections can cause the foliage to drop early, stressing the tree by robbing it of sunlight capturing foliage it needs to grow. The first defense against scab is to plant resistant varieties. If you want to grow varieties that are not resistant to scab, you will need to spray to control this disease to have healthy trees. This is especially important for young trees trying to establish. The two sulfur sprays recommended in the Basic
Disease section are for controlling scab. By spraying between green leaf tip (stage 4) and petal fall (stage 7-8), you can control scab well enough to keep your trees healthy. Combining the sulfur with potassium bicarbonate (Kaligreen, GreenCure, MilStop are some brands) can help control both scab and powdery mildew.
Raking up or mowing fallen leaves in autumn, then applying lime can also reduce scab spores overwintering on the orchard floor.
Anthracnose is one of the more serious diseases for apples grown in the Puget Sound Region, caused by the fungus Neofabraea malicorticis (synonyms Pezicula malicorticis, Cryptosporiopsis curvispora). Our maritime climate with mild year-round temperatures, abundant winter rains, and cool-humid summers is critical in the development and virulence of this disease. The canker phase is considered the most serious phase of the disease because it can cause severe damage to trees, kill newly planted trees by girdling the stems and branches, and reduce overall tree health and yield in established trees. To date, there is no apple variety known to be resistant to anthracnose.
In its disease cycle, anthracnose can release its spores potentially in all twelve months of the year. But most research shows the greatest chance of infection is in the fall rainy season, meaning mostly September through November.
In a wet year, we will do up to 3 sprays on the orchard with some form of copper sulfate. It is important to have all the fruit off the trees before you spray them in the fall. The copper is persistent and it can add off flavors to the fruit if freshly sprayed. This spray can also make red spots on the fruit. When the harvest is late, it may be early November before we can get a spray on. Our first spray goes on the minute we are done with picking. This first spray is done with leaves on the tree after harvest before fall storms arrive if possible. The second spray is at leaf drop or very soon after.
The third spray is about one month later. These sprays should be a very thorough spray “to drip” on the entire trunk and branches. It is a good idea to add a sticker such as NuFilm or Bonide Turbo Sticker to the spray, to hold the copper on the tree longer. Remember this type of spray is only a prophylactic. You have to apply it before there is a problem.
If you already have seen this disease in your orchard, these fall sprays are very important to keep the disease from spreading. You should also be ruthlessly pruning out cankers during dry weather to remove the source of further infection. Remove cankers by removing the branch at least 3″ below the canker. On young trees, you may need to remove the whole tree. Trunk cankers on older trees can be excised with a drawknife or chainsaw, followed by a flaming of the wound with a plumber’s torch. You do not want to let this disease get a foothold in your orchard!
Major Pests of Apples
Most fruit trees can occasionally suffer from common pests including aphids, leaf rollers, and leaf hoppers. Aphids and leafhoppers can be controlled with horticultural soap. Leafrollers are the larvae of a moth and can be controlled with Bacillus thuringiensis (Bt). For apples (and occasionally pears) in the Pacific Northwest, two major pests can be a problem: codling moth and apple maggot.
Codling Moth is a common pest of apples Western Washington. The adult moths emerge at about full bloom (of apples), mate as soon as the twilight temperatures are above 55°F, laying the first generation of eggs after mating. The eggs take 8- 21 days to hatch, and the larvae immediately bore into the fruit.
Larvae reach full growth in 3-4 weeks, emerge from the fruit and look for a sheltered place to spin a cocoon, at the base of the tree or beneath bark scales on the tree. Larvae may pupate in 2-3 weeks and emerge as a second generation of adults, or they may remain as larvae, pupating and hatching the following spring. In our cool summer climate, there are usually 1 or 2 generations each summer; in a warm summer there may be 3 generations. Fruit that has been inhabited by codling moth larvae will have tunnels, usually to the core area. Tunneled fruit will drop early.
In the home orchard, use a combination of strategies to combat codling moth.
- Sanitation in the orchard is the most important strategy. Remove infested fruit early and discard it (do not compost). You can recognize early infestation by a “sting” mark on the fruit, usually a black or brown spot, often surrounded by frass (caterpillar poop).
- Encourage birds, bats, and beneficial insects that may prey on moths. (This includes yellow jackets and bald-faced hornets.) Chickens free-ranging in an orchard will help with moth control.
- If codling moth pressures are high, it may be necessary to use an insecticide. An effective, low toxicity material for controlling codling moth and other caterpillars is spinosad, made from a naturally occurring bacterium called Saccharopolyspora spinosa. Various trade names are Monterey Garden Insect Spray, Bulls-eye Bioinsecticide, or Green Light Spinosad Lawn & Garden Spray. The addition of a 1% horticultural oil, such as All Seasons Oil, to the spray will further enhance the effectiveness of spinosad by smothering unhatched eggs. Spinosad is toxic to bees, so be sure to spray when they are not active (dawn or dusk). The best method of timing sprays is to use a phenology model, or heat unit tracking tool, to predict mating and egg-laying. This tutorial will help you set up disease and pest models, including codling moth, using your nearest local weather station.
- Historically for Whatcom County, the timing of the first spray will be late June. If not tracking heat units near you, try spraying around the 20th-25th of June – earlier in warm years, later in cool summers – and then again in 21 days. A second spray option is to use a kaolin clay spray product (Surround) that makes the fruit unrecognizable to codling moth (and apple maggot). This product is sprayed beginning at petal fall, to thoroughly coat the trees and fruit kaolin clay. Rainy weather may require spraying every 7-10 days through mid-July or until late August or the beginning of harvest if apple maggot is a problem.
- A high labor, but effective home remedy for both codling moth and apple maggot is to bag each individual fruit after the thinning is done. Heavy weight nylon footies or maggot barriers are effective insect barriers and control both codling moth and apple maggot. Slip the developing fruit into the toe of the footie, and twist it to secure. The nylon stretches as the fruit grows. Footies are available with detailed instructions through Cloud Mountain Farm Center, the Seattle Tree Fruit Society and through the Home Orchard Society in Oregon.
Apple Maggot is becoming increasingly common in Northwest orchards. Female apple maggot flies deposit eggs singly just below the skin of an apple or other host fruit. When the female lays an egg, a small but visible puncture is made in the fruit which can lead to “dimpling.” Depending on temperatures, the eggs hatch after a 3-7 day incubation period. The tiny cream-colored larvae (maggots) feed in the fruit, passing through three growth stages. Maggots are about 3/8 inches long. The damage caused by the maggot resembles a series of brownish, irregular tunnels called railroading. The tunnels are enlarged by bacterial decay that often follows apple maggot damage. Damaged fruit eventually becomes soft and rotten and cannot be used.
Sanitation in the orchard is crucial. Remove all fruit with signs of maggot and dispose of it (do not compost). If setting up a tracking tool for codling moth, also add the model for apple maggot percent emerged to determine when apple maggot flies may be present (mid to late July is common).
- For light infestations, hang traps in the tree canopy, either red sticky traps– (red balls shaped like apples, or red apples from the grocer, coated with Tanglefoot) or yellow sticky cards with an attractant, to help reduce the adult population.
- Traps can also be used to monitor for adult flies to time insecticide sprays. Spinosad is effective, but may need to be reapplied every 14-21 days, with a maximum of 3 sprays. The reason for limiting sprays is to avoid building resistance to spinosad in the apple maggot fly population. Spray only when bees are not active. Neem extracts can also be used in rotation with Spinosad.
- Placing physical barriers on the fruit is labor-intensive but very effective. Nylon footies are effective insect barriers. The lighter weight is effective at preventing apple maggot infestation, and the heavier barriers can control both codling moth and apple maggot. Slip the developing fruit into the toe of the footie, and twist it to secure. The nylon stretches as the fruit grows. Footies are available with detailed instructions through Cloud Mountain Farm Center, the Seattle Tree Fruit Society, and through the Home Orchard Society.
- Kaolin clay, sold as Surround, should be applied early July through late August to provide control for apple maggot.
There are several fruit tree leafrollers that can affect apples. The larvae emerge and start feeding as the new foliage begins to grow. Left unchecked, leafrollers can stress young trees by defoliating them, they can cause unwanted branching if they feed on growing branch terminals, and they can mark the newly set fruit.
Add Bacillus thuringiensis to pre-pink and petal fall sprays. Remove egg masses from the bark in winter.
Frequently asked question: “When are my (Honeycrisp, Gravenstein, Melrose, etc.) apples ripe?”
One way to tell if an apple is ripe, of course, it to taste it. For early ripening varieties that won’t store well, that is a fine way to test for ripeness. Background color can be another good indicator. On many apples, the background color will change from green to cream or light yellow when the fruit is close to ripe. Most varieties also are easier to pick if ripe, the stem easily detaching from the spur when lifted and twisted slightly.
Experience will help you determine when to pick later ripening varieties for storage. Cutting across the core to see if the seeds are beginning to turn brown is one clue, although some early apples’ seeds don’t turn until they are fully ripe. Another tool that can help is a starch test. As the fruit ripens, the starch slowly converts to sugar. If all of the starch in the apple has been converted to sugar, the apple is fully ripe, or even overripe, and will not store. You can check to see how much starch is left by testing it with iodine. Iodine reacts with starch, turning it blue-black. This test doesn’t work for all varieties, or every year, as weather can affect how fast the starch changes to sugar. But, along with tasting and background color, it can be a valuable tool.
To do the test, buy tincture of iodine at the drugstore, and dilute it with water at a ratio of 1 part iodine to 10 parts water. Store this solution in a spray bottle. Cut the apple across the core and spray the slice with the iodine solution. Starch will react with the iodine and turn grayish blue. The reaction happens within a few minutes. Apples that are to be stored long term should have at least 1/3 to 1/2 of their starch left.
The optimal temperature for long term storage of apples is 38°F. This is a refrigerator! If you cannot store apples in a refrigerator, the next best site will have steady temperatures below 40°F. The warmer your storage area, the shorter length of time your apples will store. For every 2°F warmer, the fruit ripens 8 times faster. If you have too many apples to store in a refrigerator, put your best fruit, picked at the correct ripeness for storage, in the refrigerator, and use the other fruit first.
Modern refrigerators are a dry environment for storing fruit. Your fruit should be stored in perforated plastic bags, and you should have an open pan of water in there to add humidity. Open the door regularly to let ethylene gas escape.
Apples that are to be stored should be the nicest ones; fruit with bruises or broken skins will not store. A good strategy is to pick the nicest of your storage apples slightly under-ripe. Do not wash your apples before storing them, but just before eating. Store these best of the crop apples in your refrigerator. Store more in an unheated garage or sheltered porch. Use the apples not in refrigeration first, saving the ones in the refrigerator for last. Check your stored fruit often and remove fruit that is not storing. For bumper crops, consider applesauce, cider, and drying!