White fuzz on Apple tree

For some gardeners, apple tree diseases seem to run rampant through their orchards each year. While this particular fruit tree is easy to grow, it certainly has its share of problems. Luckily, many apple tree diseases are easy to deal with so even a novice gardener can diagnose and treat them.

Learn to Spot a Sick Apple Tree

Many diseases and pests are associated with specific types of apple trees. However, some of these diseases are common among all apple tree varieties. Discover the typical diseases that can infect apple trees, along with how to deal with them.

Apple Scab

Starting in early spring, apple scab appears on the underside of leaves, then spreads to other parts of the apple tree. Spores are moved by spring rain, and they infect new leaves and fruit, according to Washington State University (WSU). You may find black, sooty lesions on leaves, blossoms, sepals, petioles, pedicels, shoots, and bud scales. As the scab spreads, it is most evident on young leaves as they begin to curl, twist, dwarf, and become deformed.

Scabs can be identified at first as small yellow or light brown areas on the undersides of leaves. As the scab progresses, the areas turn dark olive, brown, and black as cells die. Some leaves may be entirely covered with spots; leaves in this condition are often referred to as “sheet scab.”

The fungus that causes apple scab (V. inaequalis) overwinters in infected trees, even in cold climates. Both home gardeners and commercial growers use a combination of treatment programs to control the disease. This includes choosing disease-resistant cultivars, sanitation (removal of leaves and dead fruit from around the tree at the end of the growing season), and chemical treatments. Organically acceptable treatments include fixed copper, Bordeaux mixtures, copper soaps, sulfur, and mineral or neem oils, according to the University of California Statewide Integrated Pest Management Program.

Apple Mosaic Virus

The apple mosaic virus is common in most apple tree varieties and is evident by yellow or cream-colored spots that appear on leaves in early spring. The spots become larger as the virus spreads. Once warm summer weather sets in, the leaves will turn brown and die. This virus is most prevalent in the ‘Golden Delicious’, ‘Granny Smith’, and ‘Jonathan’ varieties, causing the most damage on these trees.

The virus spreads by propagation or root grafting, according to studies conducted by WSU. While it is still possible to have a crop of apples after the virus has infected a tree, it may be diminished by half in affected trees. There is no known treatment once a tree has been infected, and the University of California recommends removing it entirely from the orchard.

Black Pox

Black pox (Helminthosporium papulosum) is caused by a wet-weather fungus that overwinters in infected trees, forming conidium (spores) in lesions of old bark. Most common in warmer regions, the fungus is prevalent in the ‘Rome Beauty’ and ‘Grimes Golden’ varieties, according to the U. S. Cooperative Extensive System (eXtension.org). Black pox’s prime growing temperature is 82°F, while its incubation period is three to six months on fruit. You can identify the fungus by black, shiny, cone-shaped lesions that form on new twig growth. Small black lesions also appear on the fruit and eventually will look sunken in. Leaves will show signs of the disease, first as red circles that will turn brown or purple.

If you harvest early in the season, black pox may spread after the last preharvest fungicide application to unprotected new trees and growth. The best treatment for this disease is sanitation and applying chemicals. At the end of the growing season, cleaning up leaves and fruit from the ground and applying a fungicide will help to eliminate the disease and stop it from spreading to nearby trees. Use disease-free planting stock to prevent the fungus from spreading.

Powdery Mildew

Powdery mildew (Podosphaera leucotricha) is a common disease that affects many types of plants in mild climates, including apple trees. While powdery mildew fungi usually need moisture to release overwintering spores that germinate and infect the tree, the fungi can establish and grow in dry, Mediterranean climates, according to the University of California Statewide Integrated Pest Management Program (UC IPM). Crinkled and curled leaves identify this disease in the spring, as well as a gray-white powder coating on the twigs, resulting in stunted twig growth.

Powdery mildew also overwinters inside the buds of infected trees. In spring, delayed bloom indicates the possibility of infection; when they do open, the buds are covered with powdery spores. Wind blows and spreads the spores, infecting new shoots, leaves, and fruit, according to the Pennsylvania State University Extension.

If left untreated, it will result in blossoms dropping prematurely and overall stunted growth of the tree. You can treat the disease by implementing a mildewcide program and by pruning whitened terminal shoots on the trees.

Rusts

Apple trees are vulnerable to rusts. If your apple trees are planted near certain types of juniper or red cedar, they may become infected with the fungus cedar apple rust (Gymnosporangium juniperi-virginianae). This fungus infects both the apple trees and the juniper or red cedar, causing vibrant yellow-orange or reddish spots on the apple. On infected cedars, the galls are brown to reddish-brown.

A close relative of cedar apple rust, hawthorn rust is caused by Gymnosporangium globosum. Like cedar apple, hawthorn rust requires two species for it to do its damage: apple trees (or other rosaceous species, like pear and quince), along with something in the Juniperus species. Another rust with similar life cycles to cedar apple and hawthorn rusts is quince rust (Gymnosporangium species, G. clavipes), which affects young branches and weakening cedars and junipers, with cankers appearing on their main trunks. Fruit infected with quince rust have dark green lesions at the calyx, which make the fruit distort and the pulp becomes brown and spongy.

The Missouri Botanical Garden recommends the following for managing rust:

  • Pruning rust-infected parts of trees
  • Using preventive fungicides, like captan, chlorothalonil (Daconil), mancozeb, sulfur, thiram, and ziram
  • Planting rust-resistant varieties
  • Avoiding planting certain plants, like junipers, near apple trees

Sooty Blotch and Flyspeck

Appearing in late summer to early fall, these dull black sooty blotches (Peltaster fructicola, Geastrumia polystigmatis, and Leptodontium elatiu) and individual “fly specks” (Zygophiala jamaicensis) are multiple organisms that usually occur together as a disease complex known as SBFS.

Both sooty blotch and flyspeck overwinter on twigs of apple trees, according to Penn State University Extension. Wind spreads spores throughout the orchard, with infection occurring after petal fall. Fortunately, sooty blotch and flyspeck are superficial (surface) diseases that do not cause rot, and trees will not be affected, according to University of Georgia Cooperative Extension (UCG.

To avoid these diseases, UGC recommends pruning to increase air circulation and also thinning out fruit. For affected apples on the tree, UGC advises applying a bleach solution (one ounce per gallon of water) with a cloth to remove rot; although that season’s crop may be reduced.

White Rot

White rot (Botryosphaeria dothidea), or bot rot, is common in southern climates. The white rot only infects the fruit and wood, not the leaves. Infections occurring on limbs and twigs are identified by small circular spots and blisters. These spots will continue to enlarge during the growing season, eventually causing the bark of the tree to become orange in the affected areas and peel from the tree. In severe cases, the disease can cause girdling of the limbs and tree. Fruit rot will also occur, and you can identify it by the appearance of small, sunken in brown spots in light-skinned varieties. In red-skinned varieties, the spots appear as white or light brown in color.

Cankers, twigs, and dead bark are hosts to bot rot, which overwinters there and in nearby trees and wood, both dead and living. Spring and summer rains splash spores onto other parts of the tree and spread the infection, according to Penn State University Extension

The disease can be treated with chemicals and by pruning affected and dead wood each year. You should apply fungicide throughout the growing season, from bloom throughout harvest.

Stave Off Apple Tree Diseases

You can avoid apple tree diseases in many cases by selecting and planting healthy, disease-free rootstock. Iowa State University Extension and Outreach (ISU) also recommends burning plant material after removing dead leaves and rotting fruit, if your region allows it (check with local burning laws). Because many disease organisms survive in home compost piles, ISU also advises against composting when your garden has been affected by apple tree diseases. Keeping your garden maintained and practicing sanitation are important, whether you have one apple tree or an orchard.

It’s apple season — yay!

I buy apples weekly this time of year and eat one just about every day. But with an increased consumption of apples comes a bleak reality. A lot of them have this white fuzzy stuff in the middle:

Credit: Reddit

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Due to an unfortunate accident as a kid involving ice cream and a metal spoon, I can’t bite into apples, so I’m forced to slice them. This morning, as I was cutting up an apple before work, I saw it: the white fuzzy stuff.

I had sliced through the center of the apple to discover the core, and the little seed pockets had what looked like white mold.

I slid the cut apple to the edge of the cutting board, rinsed my knife, and grabbed another apple from the bunch. I cut it open. Again, white fuzzy stuff.

“What is going on?” I thought. “How can two apples picked from different spots in the stack have mold?” More importantly, I thought: “I’m starving! If I eat this, will it kill me?”

Desperate for an answer and breakfast, I had to look it up. What I found was that it isn’t mold. It’s part of the apple flesh.

According to the Penn State Extension, Kari A. Peter, assistant professor of tree fruit pathology at Pennsylvania State University, explained the “white fuzzy tufts” in an apple core are not fungal but are actually a part of the apple tissue.

The apples are “perfectly fine” and free of disease.

Furthermore, apples that actually have moldy cores where the seed cavity is filled with a blueish-white mold (as opposed to the little white “tufts”), the flesh of the apple is still edible as the mold is contained to the core. A moldy core is caused by mold spores entering the calyx of the apple and is affected by several environmental conditions.

Interesting to note is that Red Delicious, Golden Delicious, and Fuji apples are most prone to core mold; Granny Smith and Braeburn apples have smaller calyx openings and are less susceptible, according to the Penn State Extension.

If the mold from the core leeches into the apple flesh causing it to decay, that is known as core rot and something you probably wouldn’t want to eat.

So the next time you see the “white fuzzy tufts” inside an apple core, know that it’s just a part of the apple flesh.

Now, if you’ll excuse me while I go grab the peanut butter.

Scott is a social media and advertising veteran with a professional background in video games, design, production, video, graphics, writing and front-end development.

While powdery mildews don’t kill their hosts, they sure do a number on them. And that is particularly true for powdery mildew of apples and crabapples, Podosphaera leucotricha.

The apple powdery mildew attacks both cultivated and wild apples and crabapples. And it occurs in the all regions of the world that produce apples!

Powdery mildews get their name from the white spores that are produced by the mycelia (fungal threads). The disease on apples attacks virtually every stage of the plant – buds, blossoms, new shoots, leaves, and fruit.

The disease can be severe enough that no fruit form.

While fungicides are the standard treatments, there are some cultural practices that can help control this disease.

Unlike most fungal infections, apple powdery mildew spores do not require moisture to germinate. Therefore, this infection is known as the “dry weather disease.”

Read on as we at Gardener’s Path walk you through the steps you take to diagnose and treat powdery mildew infection on your apple or crabapple tree.

Symptoms of Primary Infections

If your tree is infected, the first thing you will notice is a delay of up to four days in the opening of the infected buds in the spring. These buds are covered with spores.

Next, the leaves and blossoms become covered with the fungal spores as they emerge from their buds. The spores look like a light gray or white powder, and the infected leaves curl upward.

Both sides of the leaves and tree shoots will be covered with this powder.

The flowers develop abnormally, are usually greenish-white, and don’t produce fruit.

An Infection That Won’t Stop

These spores are easily blown by the wind and cause secondary infections on new shoots, leaves, and fruit.

As long as the shoots continue growing, the leaves and shoots can continue to become infected.

The infections typically occur at night at 65 to 80 F when the relative humidity is greater than 70%. While this sounds really high, it is common on the lower leaf surface.

A white fuzzy coating on your apple tree blooms, leaves, and branches can mean one thing – the Podosphaera leucotricha fungs, or apple powdery mildew.

The disease on the leaves occurs first on the bottoms and may appear like chlorotic spots on the top of the leaves.

As time passes, the tissues that are infected develop the classic silver-gray powdery mildew appearance.

Fruit that is infected will come down with discoloration and netlike reddish brown colors. It may also be distorted and/or dwarfed.

High levels of powdery mildew at the end of the growing season can damage the tree in two ways. First, it can increase the number of infected buds, so you will have a high level of infection next spring. And second, it can inhibit the formation of flower buds, so that there will be fewer or no fruit produced the following season.

And if that isn’t bad enough, a tree that is heavily infected with powdery mildew can become susceptible to additional types of infections.

Cultural Controls

You should prune any shoots that appear white in the early spring, so they won’t spread spores.

Pruning and destroying infected areas is one basic method of control. Don’t forget to disinfect your pruning shears between trees and after you are done for the day.

Be sure and disinfect your pruning shears afterwards, and destroy all the infected plant parts, so the disease won’t spread.

Avoid the excessive use of fertilizer, especially in the late summer. This will prevent succulent new tissue from growing, which is easily infected by the fungus.

Another thing you can do to protect your tree is to plant it in a sunny area, since excessive shade, high humidity, and poor circulation all increase the chances of infection.

Fungicides

Since this is such a difficult disease to control, and it is critical to eliminate the spores that will keep infecting your tree, you may choose to apply fungicides. Be sure and choose ones that are labeled specifically for fruit trees.

You have a choice of low toxicity fungicides like horticultural oils. These include jojoba oil, neem oil, and brand name spray oils designed for fruit trees.

Classic fungicides that are used against apple scab, such as sterol inhibitors, are highly effective at controlling powdery mildew. These include myclobutanil and fenbuconazole.
Since the fungus overwinters inside buds, you should start treating your tree early in the season before the blossoms start to show a pinkish color.

The failure to spray before the blooms opens is one of the most common mistakes made in controlling this disease according to the American Phytopathological Society.

Be sure and repeat the sprays at 2-3 week intervals until the new shoots stop growing. That could mean as many as 18 sprays if your cultivar is highly susceptible!

Also be sure to continue spraying even if the weather becomes dry. Unlike most other foliar pathogens, apple powdery mildew continues its growth and spore production in dry weather.

Faithfully applying the fungicides will reduce the need for future applications.

Prevention

You can also spray sulfur fungicides before the symptoms appear.

Be careful with sulfur. You can harm the plant if you apply it within two weeks of a fungicide or if the temperatures are greater than 90 F.

This class of fungicides includes the classic Bordeaux mixture of copper sulfate and lime. This combination is highly effective at preventing powdery mildew and is certified organic. You can buy a pre-packaged mixture designed for small gardens.

These apple trees have had their trunk coated with Bordeaux mixture, a copper sulfate and calcium oxide in water. This helps to prevent a powdery mildew infection. Though fairly toxic, this method of prevention is considered organic.

The ultimate prevention technique is to plant resistant varieties! Some of the most popular cultivars are the most susceptible – Granny Smith, Jonathan, and Rome for example.

Some of the more common resistant cultivars include:

  • Braeburn
  • Britegold
  • Delicious
  • Enterprise
  • Fuji
  • Gala
  • Jonafree
  • Nittany
  • Winesap

Apple Crop Risk

Although apple powdery mildew will not technically kill your crop, it can debilitate the tree to such an extent that it could be unable to produce any fruit.

This disease is widespread on wild and cultivated apples and crabapples in every part of the world in which they are grown.

Therefore, it is critical to know the symptoms of this mildew, so you can be ready to take action as soon as you see infected tissue.

You will need to spray with some sort of fungicide – sulfur, horticultural oils, or sterol inhibiting fungicides. A strict spray schedule may help save your tree from this aggressive pathogen.

Have you successfully fought off powdery mildew on your apple or crabapple tree? Let us know how your battle went in the comments.

And if you’re still trying to identify a specific disease on your apple tree(s) then some of these guides may be of assistance:

  • How to Identify and Control Sooty Blotch and Flyspeck on Apples
  • How to Identify, Prevent, and Control Cedar Apple Rust
  • How to Identify and Prevent Southern Blight on Apple Trees

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© Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Uncredited photos: .

About Helga George, PhD

One of Helga George’s greatest childhood joys was reading about rare and greenhouse plants that would not grow in Delaware. Now that she lives near Santa Barbara, California, she is delighted that many of these grow right outside! Fascinated by the knowledge that plants make chemicals to defend themselves, Helga embarked on further academic study and obtained two degrees, studying plant diseases as a plant pathology major. She holds a BS in agriculture from Cornell University, and an MS from the University of Massachusetts Amherst. Helga then returned to Cornell to obtain a PhD, studying one of the model systems of plant defense. She transitioned to full-time writing in 2009.

Apple Tree Powdery Mildew – Controlling Powdery Mildew In Apples

You’ve worked long and hard to get your apple orchard healthy and growing. You’ve done proper maintenance and expected everything to be fine for a great apple crop this year. Then, in spring, you notice that your buds don’t open. A few days later, you see they are covered in a powdery substance, which is a white to light gray powder. Unfortunately, powdery mildew in apples has attacked your trees.

About Apple Tree Powdery Mildew

These are the spores of the powdery mildew fungus (Podosphaera leucotricha). The flowers don’t develop normally, with the blooms likely to be greenish white. They will produce no fruit. Leaves may be the first to be infected. These may be wrinkled and small.

Likely, apple tree powdery mildew will spread to the other trees in the orchard if it has not already. Eventually, it will infect new leaves, fruit, and shoots on nearby trees. By summer, much of the tree is browning. If fruit develops at all, it may be dwarfed or covered with a russeted skin; however, fruit is not affected until the disease reaches a high level.

Apple trees with powdery mildew are usually infected by spores that have blown in and overwintered in the tree. Powdery mildew develops best at temps of 65 to 80 F. (18-27 C.) and when relative humidity is high. Moisture is not needed for development. This fungus continues to grow and infect until it is stopped.

Powdery Mildew Apple Control

A fungicide spray should begin at the tight bud stage and continue until the growth of new shoots stops for powdery mildew apple control. Use a range of fungicides, with a third spray in early summer. Control in the home orchard with just a few trees may also be accomplished.

Resistant cultivars are less likely to develop major infestations. When replacing apple trees or planting new ones, consider disease resistance to avoid such issues like powdery mildew and other diseases.

Healthy trees are less likely to succumb to powdery mildew. Keep them vigorous with the right drainage, proper spacing to allow for good air flow, fertilization, fungicide sprays, and pest control. Prune apples at the right time with the right method. Well cared for trees are more likely to give back with an abundant harvest.

Pest & Disease Control for Apple Trees

As it grows, an apple tree may experience issues such as the presence of pests or diseases. Factors such as location, weather, and upkeep play a part in which issues your apple tree encounters and how well it stands up against them. Disease-resistant apple trees are easy-care options for growers who prefer a low-spray or no-spray orchard, and – for all apple trees – routine maintenance* can help keep most problems at bay.

*Examples of good practices are: adequate watering, fertilizing as needed, seasonal pruning, preventative and active spraying, fall cleanup, and winter protection.

NOTE: This is part 7 in a series of 11 articles. For a complete background on how to grow apple trees, we recommend starting from the beginning.

The following are merely intended as a means of identifying potential issues. Don’t be alarmed – an apple tree may experience a few of these in its lifetime, but certainly not all at once.

Apple Tree Pests

Aphids

Tiny, pinhead-sized insects, varying in color depending on the type. Will cluster on stems and under leaves, sucking plant juices.

Symptoms: Leaves curl, thicken, yellow, and die. Aphids produce large amounts of a sticky residue called “honeydew” that attracts insects like ants. Honeydew becomes a growth medium for sooty mold.

Control: Spray

  • GardenTech® Sevin® Concentrate Bug Killer
  • Bonide® Fruit Tree Spray

Control: Natural Spray

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil
  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray
  • Bonide® Neem Oil
  • Monterey Fruit Tree Spray Plus
  • Monterey Horticultural Oil

Apple Maggot

Adults are similar in appearance to a housefly, but smaller. Larvae are yellowish-white grubs. Traps are an option for luring adults.

Symptoms: Small, pinpoint-sting marks visible on fruit surface. Eggs are laid under fruit skin. Hatched larvae tunnel, making railroad-like mining pattern.

Control: Spray

  • GardenTech® Sevin® Concentrate Bug Killer
  • Bonide® Fruit Tree Spray

Control: Natural Spray

  • Bonide® Citrus, Fruit & Nut Orchard Spray

Bud Moth

Adult female moth is around 1/2-inch long; male is slightly smaller. Color varies from mottled gray to brown. Full-grown larvae are around 3/4-inch long. Pupae are brown and about 3/8-inch long.

Symptoms: Feeding occurs along leaf midrib and fruit. Shelters are created by rolling leaves and tying leaves to other leaves or fruit. Damage appears as tiny holes, irregular scarring, and areas of rot – generally found around the stem. Rot or corking around the stem occurs after the larvae have finished feeding and have pupated.

Control: Spray

  • Bonide® Fruit Tree Spray

Control: Natural Spray

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil
  • Bonide® Captain Jack’s™ Deadbug Brew Garden Dust
  • Bonide® Thuricide® BT

Codling Moth

Adults are moths, gray with brown patches on wings. Larvae are worms, about 1-inch long. Pests and damage are similar to Oriental Fruit Moth. Traps are an option for luring moths.

Symptoms: Affected fruits will have holes from outside to core.

Control: Spray

  • Bonide® Fruit Tree Spray

Control: Natural Spray

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil
  • Bonide® Captain Jack’s™ Deadbug Brew Garden Dust

Flatheaded Apple Tree Borer

Adults are small brown beetles that may target the graft location (in young apple trees) for laying eggs as well as damaged or sunken areas. Grubs have horseshoe-shaped heads and cream-colored bodies. Difficult to control once infested. Preventative spraying (including the ground around the roots) is a strong defense. Traps – in the form of tanglefoot-coated logs or posts that are later removed from the site and burned – are an option for luring adults.

Symptoms: A thick, gummy substance (sap) leaking from round holes on the trunk or in a crotch of the tree. Grubs tunnel through trunks, weakening and eventually killing the tree. Eggs hatch and larvae tunnel into tree’s vascular tissue.

Control: Manual

  • If infested, use a fine wire to try to pierce, mash, or dig grubs out.

Control: Spray

  • GardenTech® Sevin® Concentrate Bug Killer

Additional Resources

  • Contact local county cooperative Extension for further advice

Gypsy Moth

Adults are moths, from cream white to grayish brown. Eggs are laid in masses along bark, limbs, and other areas on the tree and can overwinter to hatch when the weather is favorable. Eggs hatch into larvae, which are black, hairy caterpillars.

Symptoms: Defoliation through feeding – in extreme cases, severe enough defoliation to stress and weaken apple trees.

Control: Site Cleanup

  • Keep site clear of dead limbs, branches, and other debris that female gypsy moths can use to lay eggs

Control: Natural Spray

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil
  • Bonide® Thuricide® BT

Japanese Beetle

Adult is a metallic-green beetle, which skeletonizes leaves. Larvae are cream-colored grubs that feed on turf roots prior to maturity. Turf pest-control may help reduce grub populations; check turf product labels for timing and control of grubs. Traps are an option for luring adult beetles.

Symptoms: Adults are often seen in groups – large infestations can cause stunted growth and stress by skeletonizing a majority of the leaves.

Control: Manual

  • If infestation is minimal, knock Japanese beetles into a jar of soapy water solution (they will become immobile when frightened as a defense mechanism)

Control: Spray

  • Bonide® Fruit Tree Spray

Leafhopper

Small, active, slender-winged insect appearing in various colors. Usually found on undersides of leaves.

Symptoms: Slows new growth; leaves become whitened, stippled, or mottled. Leaf tips may wither and die. Prone to carrying diseases to and from plants and trees; damaged caused by leafhoppers may be greater than the feeding done directly by the insect.

Control: Spray

  • Bonide® Fruit Tree Spray

Control: Natural Spray

  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray
  • Monterey Fruit Tree Spray Plus
  • Monterey Horticultural Oil

Leafroller

Pale yellow or green worms.

Symptoms: Leaves are rolled and webbed together where grubs feed. Foliage eventually becomes skeletonized with prolonged exposure to feeding.

Control: Spray

  • GardenTech® Sevin® Concentrate Bug Killer
  • Bonide® Fruit Tree Spray

Control: Natural Spray

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil
  • Bonide® Captain Jack’s™ Deadbug Brew Garden Dust
  • Bonide® Thuricide® BT
  • Bonide® Citrus, Fruit & Nut Orchard Spray
  • Bonide® Neem Oil
  • Monterey Fruit Tree Spray Plus
  • Monterey Horticultural Oil

Mites

Pinpoint-sized arthropods, appearing in many different colors depending on the type. Often found on undersides of leaves.

Symptoms: Sap feeding causes a bronze appearance in leaves. Severe infestations exhibit some silken webbing. Droughts or dry spells are advantageous for mite infestations.

Control: Spray

  • GardenTech® Sevin® Concentrate Bug Killer
  • Bonide® Fruit Tree Spray

Control: Natural Spray

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil
  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray
  • Bonide® Neem Oil
  • Monterey Fruit Tree Spray Plus
  • Monterey Horticultural Oil

Plum Curculio

Adult is brownish gray, 1/5-inch long, hard-shelled beetle with a long snout and 4 humps on its back.

Symptoms: Cuts a crescent-shaped hole in fruit skins and lays eggs inside. Grubs hatch and tunnel within fruit. Fruit may drop prematurely or have grubs/worms or tunnels inside at harvest.

Control: Site Cleanup

  • Remove dropped fruit as soon as it appears

Control: Spray

  • Bonide® Fruit Tree Spray (timing is key – just after petal fall)

Red Bug

Insects are small (1/4 to 1/3-inch long) and red with a brownish mid section and black legs. Adults make small holes in leaves and feed on developing fruit.

Symptoms: Leaves become distorted and apples rough with dimples or a series of small rust spots. Produces one generation each year with hatching occurring before blossom time.

Control: Natural Spray

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil

Scale

Usually on bark of young twigs and branches, encrusted with small (1/16-inch) hard, circular, scaly raised bumps with yellow centers. May also be on fruit.

Symptoms: Sap feeding weakens the tree.

Control: Spray

  • GardenTech® Sevin® Concentrate Bug Killer
  • Bonide® Fruit Tree Spray

Control: Natural Spray

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil
  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray
  • Bonide® Neem Oil

Tarnished Plant Bug

Yellowish-brown, winged insect that may have black spots or red stripes.

Symptoms: Damage is caused by injecting toxins into buds and shoots, causing stunted vegetative growth and sunken areas (or “cat facing”) on fruit.

Control: Natural Spray

  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray

Tent Caterpillar

Adults are moths. Caterpillars are a hairy, grayish brown with cream-colored spots or stripes down the back.

Symptoms: Encases large areas in webbing and feeds on enclosed leaves.

Control: Site Cleanup

  • Remove webs with a rake (caterpillars are removed with webs) and burn

Control: Spray

  • Bonide® Fruit Tree Spray

Control: Natural Spray

  • Bonide® Insecticidal Soap
  • Bonide® Thuricide® BT

Thrips

Tiny, slender, fringed-wing insects ranging from 1/25-inch to 1/8-inch long. Nymphs are pale yellow and highly active. Adults are usually black or yellow-brown, but may have red, black, or white markings.

Symptoms: Feeding occurs on vegetation by puncturing and sucking up the contents causing appearance to be deformed or discolored (similar to damage by mites and lace bugs).

Control: Natural Spray

  • Bonide® Citrus, Fruit & Nut Orchard Spray
  • Bonide® Insecticidal Soap
  • Monterey Fruit Tree Spray Plus
  • Monterey Horticultural Oil

Apple Tree Diseases

Anthracnose

Caused by Cryptosporiopsis curvispora – a fungus that is spread by splashing rain or irrigation. Favors cool, wet weather (like in the fall).

Symptoms: New cankers appear on bark as small circular spots that are red or purple when wet. When they enlarge they become sunken orange to brown areas in the bark. As the cankers age, bark sloughs off exposing wood beneath, or disintegrates exposing fibers that give the area a ‘fiddle string’ appearance. Cankers usually do not grow larger after first year’s growth. Brown spots appear on leaves and fruit. At harvest, the fungus may infect the fruit. Fruit lesions are circular, brown, and sunken with gray or cream centers (Bull’s Eye rot). Disease rarely kills tree, as it is usually confined to small branches and twigs.

Control: Natural Spray

  • Bonide® Copper Fungicide
  • Serenade® Garden Disease Control
  • Bonide® Neem Oil
  • Monterey Fruit Tree Spray Plus

Bitter Rot

Caused by Glomerella cingulata – a fungus that is spread by splashing rain or irrigation. Favors warm, wet weather.

Symptoms: Small, brown sunken spots on fruit. Spots rapidly enlarge and deepen, and may appear as target-like concentric rings. If allowed to persist, spots worsen and spores are transmitted to nearby fruit. Spots rot fruit to the core and affected fruit will eventually mummify. Disease overwinters in mummified fruit, diseased limbs, and narrow protected areas.

Control: Site Cleanup

  • Remove affected fruit and mummies as soon as they are detected

Control: Manual

  • Prune for air circulation and light
  • Remove dead, damaged, and diseased limbs whenever they appear

Control: Spray

  • Bonide® Fruit Tree Spray
  • Bonide® Captan Fruit & Ornamental

Control: Natural Spray

  • Bonide® Copper Fungicide Spray or Dust

Black Rot and Frog-Eye Leaf Spot

Caused by Botryosphaeria obtusa – a fungus that is spread by splashing rain or irrigation. Favors warm, wet weather.

Symptoms: On Fruit – Fruit infection can begin as soon as fruit begins to develop and will appear on young fruit as red flecks that develop into purple pimples. These spots do not grow much until fruit begins to mature. Spots on mature fruit are irregular – black with a red halo appearance. As the spots enlarge, a series of concentric rings form, which alternate from black to brown. Lesions stay firm and are not sunken. Fruit mummifies and remains attached to the tree. Rotting occurs in seed cavity or around core, caused by early infections, but these fruits tend to fall within a month after petal fall with no surface symptoms. On Foliage – Leaf symptoms begin 1-3 weeks after petal fall as small purple flecks. These enlarge into lesions with purple margins and tan- to brown-centers, resembling ‘frog eyes’. When heavily infected, defoliation may occur. On Limbs – May be reddish-brown sunken cankers on limbs. Winter injured trees, or dead, damaged, diseased limbs are highly susceptible to contracting these fungal issues.

Control: Site Cleanup

  • Remove affected fruit and mummies as soon as they are detected

Control: Manual

  • Prune for air circulation and light
  • Remove dead, damaged, and diseased limbs whenever they appear

Control: Spray

  • Bonide® Captan Fruit & Ornamental (wettable powder)
  • Bonide® Fruit Tree Spray

Control: Natural Spray

  • Bonide® Copper Fungicide
  • Serenade® Garden Disease Control

Cedar Apple Rust

Caused by Gymnosporangium juniperi-virginianae – a fungus that is spread from cedars/junipers to apple trees by splashing rain or irrigation in spring. During dry weather, spores are transferred to cedars/junipers. Spores overwinter in cedar/juniper galls to start the cycle again the following year. Requires the presence of both apple trees and Eastern red cedar trees (most common) or other plants/trees in the Juniperus genus.

Symptoms: Small, pale yellow spots are present on upper leaf surfaces. Spots will enlarge and become orange with black specks in center. A mass of fungal spikes appear on undersides of leaves. Orange gelatinous galls appear in Eastern red cedar trees or plants/trees in the Juniperus genus in spring.

Control: Spray

  • Bonide® Fruit Tree Spray

Control: Natural Spray

  • Serenade® Garden Disease Control
  • Bonide® Citrus, Fruit & Nut Orchard Spray
  • Bonide® Neem Oil

Control: Manual

  • Both hosts need to be present for the disease cycle to persist. Remove neighboring cedar trees and junipers if possible/feasible.
  • Plant rust-resistant apple varieties in areas prone to cedar apple rust. Spraying helps control rust symptoms, but will not completely control the disease.

Additional Resources

  • Contact local county cooperative Extension for further advice

Crown Gall

Caused by Agrobacterium tumefaciens – a bacterium that inhabits the soil and causes rapid, abnormal growth (developing into galls). Can spread through injury to roots in the soil as well as through gardening tools carrying the bacterium.

Symptoms: Trees appear stunted and slow growing; leaves may be reduced in size. In mature, fruit-bearing aged trees, may see little or no fruit. Woody, tumor-like growths called galls appear, especially at the crown (ground level) and below. Growths can restrict water and nutrient flow, but often the damage isn’t extensive enough to cause immediate or total death. If tree has died, inspect roots for hard, woody ‘tumors’ to identify Crown Gall as the cause. Note: Crown Gall is not the only thing that can cause stunted trees.

Control: Spray

  • Ferti-Lome® Fire Blight Spray

Additional Resources

  • Contact local county cooperative Extension for further advice

Fireblight

Caused by Erwinia amylovora – a highly contagious bacterium that is spread to different areas (blossoms, twigs, etc.) with tender growth by wind, splashing rain or irrigation, birds, insects, and so on – especially through points of weakness like insect injury, hail damage, wind-whipping, and more. Favors cool to warm wet weather.

Symptoms: On Flowers – Blossoms and fruit spurs will look brown and withered and also look as if scorched by fire. On Foliage – Dark brown or blackened leaves appear as disease spreads. Do not confuse symptoms of fireblight for symptoms of drought, salt injury, or nutrient deficiency which may also present as browned leaves. Tips of branches curl, leaving a “Shepherd’s Hook” appearance. Twigs and branches die back. On Bark – Cankers may form, housing orange bacterial ooze; the site of overwintering.

Control: Manual

  • Avoid applying nitrogen fertilizers during high-risk seasons (cool, wet springs) as tender new growth is more susceptible to infection
  • Cut back affected branches at least 6- to 8-inches below visible signs of infection. Disinfect shears between cuts with alcohol wipes or a solution of one-part bleach and ten-parts water.

Control: Site Cleanup

  • Destroy or dispose of pruning debris. Fall clean up is essential; including all mummified fruits and leaves hanging on the tree.

Control: Spray

  • Ferti-Lome® Fire Blight Spray

Control: Natural Spray

  • Bonide® Copper Fungicide
  • Serenade® Garden Disease Control

Additional Resources

  • Contact local county cooperative Extension for further advice
  • Understanding Fire Blight

Powdery Mildew

Caused by Podosphaera leucotricha – a fungus that overwinters in buds and emerges during humid, warm weather progressively throughout the growing season.

Symptoms: Whitish-gray powdery mold or felt-like patches on buds, young leaves, and twigs. Leaves may crinkle and curl upward. New shoots are stunted.

Control: Natural Spray

  • Serenade® Garden Disease Control
  • Bonide® Copper Fungicide Spray or Dust
  • Bonide® Citrus, Fruit & Nut Orchard Spray
  • Monterey Fruit Tree Spray Plus
  • Monterey Horticultural Oil

Scab

Caused by Venturia inaequalis – a fungus that overwinters in fallen leaves and pruning debris. Favors cool, wet weather (typically in spring).

Symptoms: Spots on young leaves are velvety and olive green turns black; leaves wither, curl and drop. Fruit also has spots, is deformed, knotty, cracked and drops.

Control: Manual

  • Plant scab-resistant apple trees if possible, especially in areas where apple scab is a known issue

Control: Site Cleanup

  • Remove and dispose of pruning debris. Fall clean up is essential to control overwintering fungus.

Control: Spray

  • Bonide® Fruit Tree Spray
  • Bonide® Captan Fruit & Ornamental

Control: Natural Spray

  • Serenade® Garden Disease Control
  • Bonide® Citrus, Fruit & Nut Orchard Spray

Additional Resources:

  • Contact local county cooperative Extension for further advice (including recommended scab-resistant varieties that are known to perform well in the area)

Sooty Blotch and Flyspeck

Caused by a complex of Peltaster fructicola, Geastrumia polystigmatis, Leptodontidium elatius, and Phyllachora pomigena as well as Schizathyrium pomi – fungal pathogens. Often develops together, since both diseases thrive under similar conditions. Each favors cool, wet weather (typically emerging in summer and early fall, but also seen in early spring).

Symptoms: Issues usually appear together. Olive-green smudges and tiny black dots on skin of apple. These fungal diseases survive on infected twigs and are spread by rains in spring and early summer. Symptoms appear as early as 2- to 3-weeks after petal fall. Damage is primarily superficial – little damage is done to the fruit’s flesh. Smudges or dots can often be rubbed or washed off with as little as water and some effort.

Control: Manual

  • Prune for improved air circulation and light to naturally prevent fungal issues from forming

Control: Site Cleanup

  • Collect and remove fallen leaves and fruit

Control: Spray

  • Bonide® Fruit Tree Spray
  • Bonide® Captan Fruit & Ornamental (wettable powder)

Control: Natural Spray

  • Bonide® Copper Fungicide

Other Apple Tree Issues

Bark Necrosis

This is a physiological disease – not one caused by fungus, bacterium, or virus – and has been related to boron deficiency or manganese toxicity.

Symptoms: Small elevations appear on surface of 1-2 year old wood. If the outer bark in the area(s) where these elevations occur is sliced away, dark dead areas will be revealed. May cause stunted terminal growth and in extreme cases, death of small terminal branches.

Control: Manual

  • Test soil. If pH is below 5.7, boron deficiency may be occurring. Manganese may become soluble and be taken up by the roots to cause injury. Improve soil pH with garden lime if soil testing detects low pH.

Additional Resources

  • Contact local county cooperative Extension for further advice (also for soil sample analysis)

No Blossoms or Fruit

Symptoms: Apple trees take about 2 to 5 years after planting (on average) before they bloom or bear fruit. If enough time has been allowed to pass, and the apple tree is otherwise healthy, there are a few things to do to help it become fruitful.

Control: Manual

  • Make sure a pollinator variety is present. Most apple trees require another different variety of apple tree to be fruitful.
  • Make sure your apple tree variety is recommended for your zone. Low winter temperatures can injure sensitive fruit buds, hindering the potential for fruit production.
  • Space trees far enough apart to help avoid nutrient or light competition. Adequate space encourages a healthy and productive tree. Spacing can be estimated by the mature spread of the tree.
  • Prune to help keep the fruiting wood and vegetative wood in balance so that there isn’t too much leaf development in lieu of blossom development in mature trees – or too much fruit-bud development and not enough leaves to “feed” the fruit.
  • Know your soil. Soil conditions, and the presence of necessary nutrients, help keep an apple tree’s roots supplying nutrients through its vascular system. If the soil is poor, or poorly drained, this affects the health and viability of the tree as a whole. If the tree is being over-fertilized, especially with a fertilizer high in nitrogen, it may develop lush, vegetative growth (leaves and branches) instead of developing fruit buds or blooming.

Additional Resources

  • Solving Fruit Tree Blooming & Bearing Problems
  • Contact local county cooperative Extension for further advice

Sunscald and Sunburn (Scorching)

Scorching or sunburn occurs during hot, dry growing seasons – with or without humidity in the air, but most commonly when humidity is low. Brown, crispy edges appear on leaves.

Symptoms: Sunscald is also called winter injury or “southwest injury” as it commonly affects the south-west side of tree trunks during winter. Warm, clear days cause bark to expand and nights that are several degrees cooler will cause the bark to contract, damaging cells and causing splits and cracks in the trunk.

Control: Manual

  • Protect trunks prior to winter with protective tree guards or a diluted solution of water and white latex paint (50/50).
  • Water new trees every 7- to 10-days during the growing season (if no rain within the week) or as needed (as the soil becomes dry to the touch).
  • During the growing season, consider constructing a temporary shade cloth to protect trees from the sun on hot, dry days. Water as needed (see above).

Additional Resources

  • Preparing Trees & Plants for Winter
  • Drought Issues & How to Protect Your Trees

Water Stress

Symptoms: Can relate to overwatering or underwatering. Overwatering commonly presents as pale green to yellow leaves and leaf drop. Can weaken a tree, lead to issues with root rot, and ultimately kill the tree. Underwatering often presents as discolored – often yellowed – dry leaves. Tree may appear to wilt overall and prolonged lack of water can kill the tree.

Control: Manual

  • Water new trees every 7- to 10-days during the growing season (if no rain within the week) or as needed (as the soil becomes dry to the touch).
  • If planted in a location where the soil does not adequately drain water after heavy rains (leading to standing water), relocate the tree as soon as possible.
  • If drought-like conditions persist, consider slow-trickle drip irrigation to allow water to reach the roots rather than wash over soil surface.

Additional Resources

  • Plan Ahead for Rainy Weather

Wind Injury

Symptoms: Can involve injury such as leaning trees, uprooted trees, breaks, tears, or wind-burned foliage. Depending on the severity of the injury, an apple tree can either bounce back from minor damage or succumb to the wind-caused harm. This is determined on an individual basis and the health of the tree before the damage occurred.

Control: Manual

  • Adequately tamp soil around the tree’s roots (and thoroughly water) at planting time to remove air pockets and ensure good contact with the soil. Air pockets and loose soil around the roots can cause the tree to rock easily in its planting hole, leaving it vulnerable to leaning or becoming uprooted.
  • Use tree stakes for new trees, dwarf trees, and trees planted in high-wind areas to help support upright growth and avoid leaning, uprooting, and breaking.
  • Selectively thin fruit that may be weighing down limbs to reduce stress from the weight, and avoid tears or breaks during gusty weather. Be aware: pests and disease may also take advantage of resulting broken or torn areas if damage occurs.
  • If tender new foliage is blown or whipped around by the wind, it may appear discolored (dark – like a burn or bruise). This damaged growth can be removed to encourage healthy, new growth to take its place.

In This Series

  • Introduction

Getting Started

  • Acclimate
  • Location
  • Planting
  • Soil Preparation

Care & Maintenance

  • Fertilizing
  • Pest & Disease Control
  • Pruning
  • Spraying
  • Watering

Other Topics

  • Harvesting

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