Diseases of Fruits

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Sooty blotch and fly speck are actually two different disease. They are mainly widespread throughout the Midwest and can commonly occur together on the same fruit. 

They both can cause a blemish or discoloration on near mature fruit. Although the discoloration is superficial and doesn't necessarily damage the fruit, we can first be visual eaters, thus this discoloration can reduce the market value and grade of the fruit. 

This is can affect all varieties of apples. However, it is most severe on yellow or light colored varieties such as Gold Delicious and Grimes apples. It mostly occurs with a cool and wet spring, rains in the late summer and lower temperatures in the the early fall. 

Sooty Blotch has a brown to dull black sooty blotches with an indefinite outline on the surface of the fruit. In more severe cases, the blotches cover the entire outside of the fruit. 

Fly Speck come in groups of 6-50 (some cases even more) black and shiny round dots that resemble fly excreta. The individual fly specks are clearly separated and can easily be distinguished from sooty blotch. 

Sooty blotch is a disease complex caused by a large number of different fungi while Fly Speck is caused by Zygophiala jamaicensis. Both of them overwinter on twigs of various woody plants in the wild. Especially, wild blackberry and raspberry canes. Both fungi require free water on the surface of the fruit in order to infect the fruit.  

In order to control, you must find an orchard site that always has full sunlight, good air circulation and good soil and water drainage.  You also need to prune trees annually to open center for maximum air circulation. Remove or destroy wild or neglected apple trees. Backyard growers should remember that this disease is superficial and does not typically affect the quality of the fruit itself. Just wash, rub or peel the fruit and you are good to go with eating them or cooking with them. 

Scab occurs all throughout the Midwest too. Wherever apricots, plums, nectarines and peaches grow, you are sure to find some scabs. This disease does affect the fruit along with leaves and young green twigs. Scab is most commonly found within home orchards where fungicide prevention is typically not done. In larger and more commercialized orchards, they conduct fungicide spray programs which greatly reduces any loss from scabs. 

Wet conditions during spring and early summer after the first petal fall are the perfect makings for a severe attack by this fungus. The disease is typically more serious for those trees where branches are low lying and shade (where air movement is minimal or non-existent). 

When it comes to the symptoms of this disease, they will first appear half formed to nearly full grown within 6-7 weeks after the first petal fall. Spots start around the stem end (where sun exposure is more prevalent). These spots are superficial and will over time, slowly enlarge. Scabby fruit will also drop prematurely in most cases and do not store well. Leaves around the scabs might become infected too. Diseased leaves may dry up and drop out/off, leaving what is referred to as "shot holes". If it's been a really rainy season, you can almost bet that the scab-infected leaves are going to drop early. 

Scab is caused by a fungus called Cladosporium carpophilum. Like the previous, this scab fungus overwinters in twigs infected the previous years. You can control it by avoiding low lying or overly shaded sites when planting. Air flow and soil drainage are critical too! Do not plant near wild or neglected peaches, nectarines, plums and apricots. Backyard growers should be reminded that this is a superficial disease. If the infection is not severe, the quality of your fruit should not be an issue. 

Downy mildew of blackberry is caused by a fungal-like pathogen and this disease is systemic. Nearly every cultivator of blackberries is susceptible to downy mildew, unfortunately. This disease not only affects blackberries, but, boysenberries, youngberries and rose berries are at risk too! Downy mildew affects both the leaves and the actual fruit of the blackberry. The leaf symptoms are most commonly found right here in Ohio.

When this disease occurs, it can manifest even when foliar symptoms are not yet visible. This disease is at its most severe during wet weather, accompanied by cool to warm temps (usually between 65-75 degrees). 

Management of blackberry downy mildew requires you to take an integrated approach because there are no resistant varieties. Because of this, this disease is systemic and the usage of fungicides is critical to prevent the spread of the disease to developing fruit.

There are varieties that are more/moderately resistant than others, however. Those varieties include:

*Chester

*Arapahoe

*Apache

*Navaho

When you are planting new starts, please always select a site to plant that has direct sun for at least 8 hours per day and provides good clear air flow. Do not plant near any wooded areas with wild blackberry bushes or roses. Both can be a source for seasonal downy mildew spores. Once your new starts begin to be established, remove their suckers and weeds at their bases, so that air circulation is good! 

If you suspect you have found downy mildew, you can always take a sample to our friends over at the C. Wayne Ellett Plant and Pest Diagnostic Clinic at The Ohio State University. Or, if you are not in the great State of Ohio, find your states pathology specialist to assist you in the identification of your suspicion. 

When looking for the most serious of all diseases of both sweet and sour cherries, look no more. Cherry Leaf Spot IS the most serious of all diseases for them! While it mainly affects the leaves, lesions are also known to appear on the actual fruit itself. It can also affect the petioles and fruit stems. A good way of telling whether or not your cherry tree is affected by this, is to watch for leaves that drop prematurely and defoliate by mid summer. Those are usually telling signs that your cherry tree has Cherry Leaf Spot disease. 

So many times of this occurring on your cherry tree(s) prematurely, can without doubt result in:

*Dwarfed and unevenly ripened fruit with a yucky taste

*Devitalization of trees can make the trees more susceptible to winter injury

*Fruit spurs dying

*A decrease/reduction of size and fruit set

*Small and/or weak fruit buds

*Reduction of fruit growth

*Lastly, the eventual death of the tree entirely

Toward the end of May and the beginning of June, a small, circular purple spot may appear on the upper surface of the lead. Eventually, the spots get larger and turn a reddish brown color. Lesions might even emerge to produce large, irregular spots that can eventually consume in its entirety. On sour cherries especially, one of the main symptoms is the golden yellowing of the older infected leaves before they eventually just drop off. This symptom may not happen every season. The spotting of infected leaves will always be visible. All things considered, this could actually cause your cherries to ripen unevenly. Spots themselves do not typically form on the cherries themselves. Along with most others, this too is caused by a fungus. 

To control, you must collect and destroy the fallen cherry leaves in late fall/autumn. This should actually prove beneficial (especially for back yard growers) with one or a few trees. This is not a recommended practice for larger commercial plantings. 

Cherry Leaf Disease has a leaf spot disease cycle. New York State Agricultural Experiment Station provides an excellent visual aide that makes for an easy view of this cycle (specifically, The Tree Fruit Crops IPM Disease Identification Sheet #8). 

This is more of a springtime disease. It mainly affects peaches, nectarines and comparable ornamental plants. It might not always be an issue every spring time, however, it can be on the more serious side in terms of severity , during cooler, wet spring seasons that follow mild winters. 

The majority of damage comes to peach trees by way of the fungus that is considered leaf curl. This will ultimately cause an early dropping of leaves. 

Affected peach trees that become weak will also more than likely produce much fewer peaches the following season. That can be further reduced when the tree is a younger tree and its blossoms are not plentiful as compared to older, more mature trees. 

Some of the symptoms of this disease include:

*Leaves that are still in the developmental stage can become very distorted (thick and puckered)

*Have reddish or purple case

*Eventually the leaves become powdery gray

*Leaves will turn yellow or brown or even drop

As the others preceding this one, this too is caused by a fungus called Taphrina deformans. It survives the winters while sporing on the bark and buds. Infection then starts very early into the growing season. New leaves can then become infected and result in off shoots of other spores. 

The good news is that this is not impossible to control. It's actually quite easy since the fungus survives the winter on the surface of the buds and twigs. Using a basic fungicide spray and thoroughly covering the entire tree will give that control needed. Make sure to space new plants and do not over crop, as that will inevitably cause the tree to weaken and make it more susceptible to winter injury. A good resource for larger crop growers when choosing fungicides for this disease is the Midwest Fruit Pest Management Guide (specifically Bulletin 506) . A good resource for back yard growers would be Controlling Diseases and Insects in House Fruit Plantings (specifically Bulletin 780).

This disease is also commonly referred to as "Bot Rot", derived from the BOTryosphaeria word. This disease is actually a fungus. This fungus can actually cause cankers on the limbs as well as any above ground woody portions of the tree that is infected. In cases where the tree has experienced drought, injury in the winter, sunscalding, pruning that has been done poorly, unbalanced or low nutrition, as well as a host of other plant diseases. 

This fruit rot is very tricky! It can at times be sporadic in appearance. In one season, it might be very serious and widespread. Yet, the following season may yield cases that are few and far between. Here in Ohio, a wide range of woody plants are affected and very common. 

A few very susceptible apple varieties are:

*Dutchess

*Golden Delicious

*Grimes Golden

*Gallia Beauty

*Rome 

Yellow Transparents

A couple of apple varieties that are less susceptible are:

*Jonathan

*Red Delicious

When you first notice this, you may see small, reddish brown spots that can show up near/around the lenticels. Over time, the spots will enlarge and feel soft and sunken/depressed. The varieties that are more in the yellow skinned may be bordered by one or multiple red "halo-like" rings. Sometimes on red varieties, the skin can often become bleached. That is because the tissue under the spots is soft and egg shaped with more of a longer axis that is parallel to that of the core. Over time, the spots may completely consume the entire fruit and the entire skin becomes fark brown and superficially will resemble black rot. The only difference with that is the decayed tissue will be firm instead of soft. Exudate in the form of beads, will appear on the outer surface of fruits and that is completely rotted by white rot. Mature fruits are mainly the ones that stay most susceptible to this disease. 

You can control this disease through proper sanitation. Clean up pruning's from the perimeter of the orchard and burn them. Really, any practice that assists in maintaining healthy, vigorous conditions will be critical for controlling the canker phase of this disease. Fungicides are not generally useful with this disease. Environmental dedication is what is needed most. 

No. This is not the famous television show type glam. This has actually been something has plagued many peach orchards here in the great State of Ohio! It is very very destructive, once it establishes itself in an area or orchard. It has been also located in the province of Ontario, Canada and those states primarily in the Great Lake states. 

There is a range of distribution with this disease. That range corresponds with wild chokeberry, which serves as a mega reservoir for this infection. X-disease can affect the following:

*Peach

*Nectarine

*Sweet Cherry

*Sour Cherry

Cherries and Peaches will vary depending on their environment amongst other factors. Once you recognize the other symptoms though, you will be able to also recognize the disease more often than not. 

What are the symptoms, you ask? Well you're in luck! Here's a quick symptom guide:

*Peaches- they are the easiest of all to identify this disease! Leaves start to curl inward and develop irregularly. Yellow to reddish/purplish spots start and then eventually leave a shot hole and tattered leaves. 

*Cherries-It's really all about the rootstock here! Trees that are on mahaleb rootstock die suddenly in the midsummer by this disease. While trees that are on mazzard rootstock have a slow decline to eventual death. X disease is believed to be caused by a virus until structures resembling mycoplasma were discovered. Mycoplasma are small, parasitic organisms that have long been shaped bodies that are smaller than bacteria but larger than most virus particles.

Eradicating chokecherries near stone fruit orchards are going to help most with control measures. Chokecherry bushes are more so found in hedges along property lines and in open woods and in overgrown meadows and/or abandoned fields. Large mowers/Brushhogs are the best and most efficient way to get those chokecherries down efficiently and effectively. You can go deeper by bulldozing, deep plowing and burning. Or, if you just have a small patch, youi can always pull them individually. Always check the sprouts. Sprouts and new seedlings should be treated with herbicide sprays and pulled in the summer to prevent/minimize re-growth. 

**Caution: Chokecherries are confused a good majority of the time with wild black cherries and wild pin or fire cherries. It is important to distinguish the species from one another. Unlike black and pin cherry (which can grown up to and beyond 50 feet), they are usually found in clumps. Chokecherries are wider and broader than black or pin cherry leaves. Look closely at the serrations along the margin of the leaves. They will be more prominent and spreading than those of the other two species. 

This is one of those pesky fungus' that can stunt the growth of all it comes into contact with. It is very damaging to the foliage. When it attacks the foliage, it becomes distorted and causes a reduction of growth. As well, the surface of the fruit itself can become russetted or discolored and even dwarfed. On trees with a substantial or great amount of mildew on them, weakness and increased susceptibility of other pests and winter injury will surely occur. 

The symptoms of this are really all over the place vs one concentrated area of the tree, twig or fruit. This mildew can be found on the following:

*buds

*blossoms

*leaves

*twigs

*fruit

At first, you may see it appear in the springtime on the lower surface of leaves (usually at the ends of branches). It is a small, white felt-like patch of fungal growth. In a matter of time, it will consume the entire leaf. Eventually, leaves will become narrow, crinkled, stunted and brittle. By around mid summer, small black specks will show up on the lower leaf surface in some cases. Most commonly though, you're going to see them more along the twigs. All these are, are fungal fruiting bodies. Their level of importance in the entire disease cycle however, is minimal. 

Where the fungus spreads at a more rapid pace is going to be those twigs. The twigs are going to eventually stop growing altogether and result in stunting. There have been cases, where the twigs will be killed back. This will cause leaves and blossoms from those infected buds to be diseased from the start the following spring.  Infected blossoms will shrivel and no fruit will even produce. The tricky part in all of this though, is that you may not even be able to notice the disease until the disease has built up enough to reach high levels. Fruit that is diseased has a fine network type of surface blemish that is called russetting. Word of caution: Even at lower temperatures, some powdery mildew can survive. 

This is controllable in many instances. The apple varieties can vary in their susceptibility to powdery mildew though. 

The varieties that are very susceptible include (and should be avoided if powdery mildew is a problem):

*Jonathan

*Granny Smith

*Mutsu (Crispin)

*Rome

*Cortland

*Baldwin

*Monroe

*Idared

Always plant the trees in sunny locations that also have good air flow. This will actually help in reducing the humidity around the trees which can aide in reducing the chances of this disease. Fungicide sprays can also be used. Back yard growers should refer to Controlling Diseases and Insects in Home Fruit Plantings, Bulletin 780, which is a publication through your local Extension Office or the CFAES Publications. 

Of all of the plant/tree based mildews, this one takes the cake in terms of seriousness and destructiveness. Especially in the Midwest and Northeastern United States. It is caused by a fungal-like pathogen called "Pseudoperonospora humuli". In wet weather and more of the mild temps, it reaches its severity. It is also systemic and can cause significant decreases in the yield and declination and eventual loss of quality. 

This pathogen survives the winter in dormant buds, crowns or plant debris in the soil. In the springtime, the pathogen moves systemically into the basal spikes. Spikes that are diseased will become stunted, pale green and even brittle. The upper side of the leaves will have yellow spots that form. These spots over time will turn brown and end up with a crusty like appearance. On the under side of those leaves, you will see dark purple/almost black spores, especially during wet or foggy weather when temps are around 60-70 degrees. Word of caution: Spores are spread with wind. So if really windy, spores can initiate new infections on new leaves, aerial spikes, flowers and cones. 

When it comes to managing this, it is best managed by integrating resistant varieties, cultural practices and chem control. Back yard and organic growers are strongly encouraged to plant resistant cultivars in order or reduce or even eliminate the need for any fungicides. 

When we compare Cultural Practices vs Chem Control, here is the difference:

Cultural Practices include:

*Cut foliage off the crown

*Remove said foliage and destroy it

*Train bines early to prevent them from coming into contact with the soil and diseased aerial spikes

*Remove the lower leave, suckers and weeds starting in the early spring and continuing into the season

Chem Control include:

*Fungicides (Pre and Post harvest)

There are primarily three varieties of rust with this disease. These rust diseases can occur on apple and crabapple trees here in Ohio. ALL of them are caused by different species of the fungus called "Gymnosporangium" (say that fast 5 times in a row).  Each one has various junipers and red cedars. These act as "hosts". Apples are generally the fruits that remain most susceptible to this infection. Typically it takes the rust fungi between early bloom until about 30 days after that early bloom in order for the infection to appear or make itself known to the tree/trees it is contained. 

The first variety is "Cedar-Apple Rust on Apple"

This reveals itself during May or June. During those months, you may see pale yellow spots that will pop up on the upper surface. Spots are around 1/4 in in diameter and with time, the spots will turn orange with often times a reddish border. Sometimes, black fungal bodies show up and form within the spots. At that point, it might exude an orange fluid. On fruit though, similar yellow-orange spots will appear, but those are near/closer to the calyx end. These are usually more visible on younger or immature fruits and are typically much larger than those that show up on the leaves. 

The second variety is "Cedar-Quince Rust on Apple"

This will on affect the fruit of apples. It will cause the fruit to pucker at the blossom end and that will eventually develop a sunken, dark green area. Eventually, the dark green will turn into a brown area that is spongy in texture. Apples are very susceptible to cedar-quince rust from the early bloom all the way to the third cover. 

Lastly, is the "Cedar-Hawthorn Rust on Apple"

This is similar to those leaf spots that are very similar to those found on apples and crabapples. Large spots that range from gray to brown will form on the leaves of hawthorn. Fruit infection on apples is very rare. Mostly, you will notice defoliation and deformation of fruits and twigs that might occur on hawthorns.  Aecia may form on apple and crabapples, few and far between, but may still form nonetheless. 

Within 5-6 hours after landing on the leaves, sporidia attach to the surface, germinate and penetrate the cuticle and upper leaf surface. After about 10-14 days, the yellow spots will develop on the upper leave. Several weeks later, carried by wind, aecia will produce. 

How do you control these?

Always grown resistant or immune apples, crabapples and junipers. Always check with your nursery or store you purchase at, whether or not they know if they are rust resistant. If the nursery or store you purchase from cannot tell you that, choose another place to purchase. 

Destroy all nearby wild or worthless junipers that are almost certain to be infected with rust galls. 

Finally, where rust is problematic, follow a strict fungicide protocol/spray program. Backyard growers are always referred to the publication called Controlling Diseases and Insects in Home Fruit Plantings, specifically Bulletin 780. This publication can be found at your county Extension office or via the CFAES Publications online.