Diseases of peach trees

Tree Fruit Update: August 7, 2014

Mary Concklin, Visiting Associate Extension Educator – Fruit Production & IPM

Pre-Harvest Drop Control: Water, ReTain, NAA, Insect & Disease injury.

These all go together because of the interaction they have on the effectiveness of your drop control. Any condition that puts trees under stress will reduce the effectiveness of drop control, including heavy mite infestations (there are too many bronzed trees around the state), heavy scab or other disease pressure, and drought conditions. Across the state, rainfall amounts (www.newa.cornell.edu) for July have averaged 3.5” with a range of 3.01”-5.5” with one location reporting only 0.11”. In August so far, the average rainfall has been 0.26” with a range of 0”-0.79”. Eliminating the 2 locations at the much higher and much lower ends, the combined July-August average rainfall for much of the state is 3.4” or 0.68” per week – well below what is needed to support the trees and the crops. Also keep in mind that when it has rained, it has not always been a good soaker, only enough to keep the dust down in the fields, which does very little for reducing drought stress. Supplemental water has been and continues to be critical.

With that in mind, in blocks not under stress, apply ReTain (7 day PHI, 12 hr REI) 2-4 weeks before anticipated harvest for 7-10 days drop control, at the rate of 1 pouch/acre. Apply with an organosilicone surfactant and apply under slow drying conditions such as early morning or evening hours. Spray water pH should be 6-8 and may be easily checked with a pool pH test kit. For information on split applications of ReTain and ReTain plus NAA, refer to the 2013 article I sent out last year by Dr. Duane Greene, UMass. Click on the following link: http://ipm.uconn.edu/documents/raw2/html/456.php?aid=456.

What causes peach leaves to turn yellow, red, have shot holes?

There are many causes and they are not always easily distinguishable.

Overwatering or peach trees in poorly drained soils. Of course this will also kill the roots and lead to a much shorter life for the tree. Improve drainage PRIOR to planting. Know the amount of water the irrigation system is putting out and limit it to 1”-2” per week depending on tree age, crop load and rainfall received.

Bacterial Spot, caused by Xanthomonas campestris pv. Pruni, infects peach leaves and fruit. Foliar symptoms appear as red spots and as the season progresses, the red spots become holes giving the leaves the shot-hole appearance. This is a very difficult disease to get rid of and has been discussed in earlier emails this past spring. Maintain healthy trees free of stress.

Nitrogen deficiency doesn’t always manifest itself as just pale green leaves. Severe deficiency symptoms also include a reddish coloration of the leaves and red or brown spots that may eventually drop out. (Photo from UC Davis)

Chemical toxicity, specifically from copper applications, causes red or necrotic spots that often times lead to holes in the foliage. Because of this, only early season applications of copper for disease control are recommended. Even low rates applied after bloom have been known to be phytotoxic.

X-Disease, caused by a phytoplasma and moved by leafhoppers is not very common. However, once in the tree it will shorten its life. Injections of antibiotics had been tried many, many years ago but are no longer recommended. Remove chokecherries – an alternate host – and other infected peach trees, and maintain healthy trees.

Common Peach Diseases: Peach Tree Care For Sick Trees

Grow a peach tree in your yard and you’ll never go back to store-bought. The rewards are great, but peach tree care calls for some careful attention so they don’t fall prey to some of the common peach diseases. It’s important to learn common peach disease symptoms so you can get a jump on managing them and avoid these issues in the future.

Is My Peach Tree Sick?

It’s important to watch for peach disease symptoms so you can treat your tree as quickly as possible. Peach tree diseases and fungus are common problems, and can affect nearly any part of the tree. If your tree seems to be ailing or your fruit doesn’t look right, read on.

Common Peach Diseases

Here’s a quick rundown of some of the most common types of peach tree diseases:

Bacterial Spot – Bacterial spot attacks both fruits and leaves. It produces purple-red spots with white centers on leaf surfaces that may fall away, leaving a shot-hole appearance in the leaf. Bacterial spot on the fruit starts with small dark spots on the skin, gradually spreading and sinking more deeply into the flesh.

Fortunately, damage on fruits can be cut out and the fruit still eaten, even if they don’t look good enough for the produce market. Good cultural care is critical for preventing bacterial spot. A few partially resistant peach varieties are available, including Candor, Norman, Winblo and Southern Pearl.

Brown Rot – Brown rot is arguably the most serious disease of peach fruits. Brown rot fungus can destroy flower blossoms and shoots, beginning at bloom time. You can recognize it by the small, gummy cankers that appear on infected tissues. It will spread to your healthy green fruits when wet weather sets in. Infected fruit develop a small, brown spot that expands and eventually covers the whole fruit. The fruit will ultimately shrivel and dry up, or “mummify” on the tree.

You’ll need to remove and burn all mummies from the tree to break the brown rot life cycle. Consult with your local garden center, an agricultural extension agent or a certified arborist about applying a fungicide to ward off the fungus for the next harvest.

Peach Leaf Curl – Peach leaf curl can appear in the spring. You may see thick, puckered or distorted leaves with a red-purple cast begin to develop instead of your normal, healthy leaves. Eventually, leaves affected by leaf curl will grow a mat of gray spores, dry out and drop, weakening the tree itself. But, once this first round of leaves has dropped, you probably won’t see much of this condition for the rest of the season.

A single spray of lime, sulfur or copper fungicide all over the tree each winter should prevent future problems with peach leaf curl.

Peach Scab – Peach scab, like bacterial spot, is for the most part, just an aesthetic problem. Small, dark spots and cracks appear on the surface, but may be so numerous they grow together into large patches. Shoots and twigs might develop oval lesions with brown centers and raised purple margins.

It’s important to increase the air circulation in the tree’s canopy by pruning it, severely if necessary. After the petals fall, you can spray with a protectant fungicide, like wettable sulfur. Treat the tree with spray five times, at 7- to 14-day intervals after the petals have fallen.

Peach Yellows – Peach yellows is a common problem in trees that aren’t already on a spray program and is transported by leafhoppers. Leaves and shoots may emerge in a deformed manner creating clusters, or witches brooms. Fruits from trees suffering from peach yellows will ripen prematurely, and are likely to be bitter and of poor quality.

Peach yellows may only affect part of the tree; however, there is no cure for this problem – once the symptoms are obvious, removing the tree is the only option.

Peach trees can be vulnerable but, with good, attentive peach tree care, you’ll have perfect peaches and healthy trees.

The leaves of my peach tree have strange, puffy, pinkish growths that I’ve never seen before. What is this?

Peach leaf curl is a common and widespread disease of peaches. In Nebraska it is found wherever peaches are grown, but it is usually not severe in the drier areas of western Nebraska. The disease is favored by the milder, wetter climate of eastern Nebraska. Although leaf curl is principally a disease of peaches, nectarines also can be infected. Related fungi of the Taphrina genus cause similar diseases such as plum pockets on plums and leaf blisters on oak, maple, and elm.

Peach leaf curl, caused by Taphrina deformans, is easy to recognize. The most characteristic symptoms are curling and crinkling of the leaves as they unfurl in spring. Usually, the entire leaf is affected, but sometimes only small areas are involved. In addition to curling, diseased leaves are thickened and often turn red or pink. As the season progresses, diseased leaves turn gray and appear powdery. This is the result of the fungal pathogen producing spores on the leaf surface. Eventually, the leaves turn yellow or brown and are prematurely cast.

This disease may also occur on fruit, blossoms, and young twigs. Diseased fruits are distorted, swollen, and exhibit discolored surface areas. These areas are usually wrinkled and lack the normal peach fuzz. Infected fruits seldom remain on the tree until harvest. A severely disease tree does not yield well and is subject to winter injury. Plum pockets, a disease caused by Taphrina communis, causes similar symptoms on plum leaves, while the plums become distorted and puffy. This disease is not considered a serious problem in most cultivated plums. Wild plums, however, are highly susceptible. If necessary, the same control procedures used to prevent peach leaf curl may be used to minimize plum pockets.

Fungal spores are produced on the surface of diseased leaves and are washed or blown onto twigs and leaf buds. When these buds break open in the spring, the spores come in contact with the young, unexpanded leaves. When environmental conditions are cool and wet, the spores germinate and infect the leaf tissue. Infected cells do not develop normally due to the secretion of growth regulating chemicals by the fungus. This results in abnormal cell division and enlargement giving the leaves a curled and crinkled appearance. Only expanding leaves are susceptible to infection.

Control
Fortunately, peach leaf curl is one of the easiest fruit diseases to control. In most years, leaf curl can be effectively prevented with a single application of an appropriate fungicide, including lime sulfur, chlorothalonil, Bordeaux mixture, or a copper fungicide. Because infection occurs when the buds begin to swell, the fungicide must be applied during the dormant season. In Nebraska this can be done in the fall, after the leaves have dropped, through late winter. Remember, for effective disease control the fungicide must be applied at the proper time, and the tree must be thoroughly covered with the fungicide spray. When applying any fungicide, be sure to read and follow the label directions.

Peach tree disease is a broad term used to describe problems affecting the tree itself and the fruit. Prevent many peach tree diseases by careful selection of cultivars, good gardening practices, and a maintenance schedule.

Fungal Diseases

There is a host of fungal diseases affecting peach trees. With the ability to live in the soil for years, fungal spores move to the peach tree through water splashing onto the tree or through dispersal by the wind. Below are the major fungal problems associated with peaches:

Brown Rot

One of the most serious and common diseases affecting all portions of peach trees, brown rot causes the fruit to rot away on the tree and one can lose and entire year’s harvest. Brown rot is caused by a fungus, Monilinia fructicola. The fungus lives in many temperature climates among other trees, leaves and more. It spreads by spores through the wind and loves moist climates, so you may notice this disease after a wet spring or a rainy season.

The problem rears its ugly head during flowering, with the infected flowers wilting and browning rapidly. The flowers then infect the shoots, with gooey cankers appearing that eventually infect the green, immature fruits. Instead of falling, peaches remain on the tree developing brown spots that eventually cause the entire fruit to rot and turn into mummies, which continue infecting other portions of the tree.

To prevent brown rot, always clean up rotted fruits from the ground and remove affected fruit from the tree. Don’t compost them, since the fungus spores can live in compost, and if you spread the compost in the garden, you’ll only perpetuate the disease cycle. Use a fungicide such as Captan and spray the tree when it blooms, repeating two weeks later. If you’re planning a new peach orchard, make sure to plant the trees far enough apart to allow good air circulation and sunlight, which can reduce the spread of the fungus and keep the area dry, which prevents spores from developing.

Peach Scab

Like brown rot, peach scab is caused by a fungus, Cladosporium carpophilu and is most noticeable after the first season of fruiting. It’s prevalent in the warm, moist, humid south but it can affect trees anywhere. The fungal spores overwinter in the soil or on infected twigs and splash upon the tree during rainy conditions. This fungus causes brown spots on the fruit resembling freckles and if severe, the spots join together forming large lesions, as well as lesions on twigs and leaves. Sometimes the fruit will crack, and rot may appear in the cracks. While scab won’t affect the taste, they make it harder for the peach skins to slip off during the canning process, so if you plan to preserve the harvest avoid any fruits spotted with scab.

To prevent scab, spray the entire tree just as the petals begin to fall with the fungicide Captan and repeat every two weeks until the fruit is about a month away from harvesting. It’s important to treat the tree with the fungicide during its first two years of developing fruit. Pruning to allow proper circulation of air, not planting in low-lying areas where water develops, cleaning up fallen fruit and leaves from the orchard, and a rigorous regimen of spraying during flowering helps prevent this disease.

Powdery Mildew

Caused by a fungus called Sphaerotheca pannosa, powdery mildew affects garden plants as well as fruit trees and peaches are most susceptible when roses are planted nearby. The fungal spores overwinter in the dormant buds and are spread by the wind and are most noticeable during warm and wet springs. Affected leaves may fall off or they may develop abnormally. You can see white fuzzy spots growing on the green, immature fruit, but the symptoms of the fungus usually go away as the fruit reaches its ripening stage, though the infected area browns, and the skin turns leathery. While not a major problem for most home gardens if powdery mildew strikes it can ruin the entire harvest. Most peach cultivars are bred to resist the disease.

To prevent powdery mildew, keep the orchard area clean by raking up fallen leaves and fruit and prune to open up the tree and allow adequate air circulation. Before bud break, spray the tree with a myclobutanil fungicide.

Leaf Curl

The disease leaf curl, caused by the fungus Taphrina deformans is most prevalent when conditions are wet and cool in spring and when leaves are just starting to bud out. The fungus overwinters in the soil and on foliage and spreads when water splashes onto the tree. Infected foliage changes from green to reddish, and then puckers and curls. The affected leaves eventually turn brown and either fall or remain attached to the branches. Unless conditions remain wet, a second set of normal and unaffected leaves replace the infected ones. Leaf drop can affect the proper growth of the tree and the production of fruit.

The fungus also infects young shoots, causing stunting and distorted growth, with the shoots eventually dying. The infection rarely affects the fruit, but when it does, the affected areas turn corky and split.

If left untreated, leaf curl can eventually make the peach tree so unhealthy you’ll have no choice but to remove it and discard. Prevention is as easy as spraying the tree while it’s still dormant with a copper fungicide and repeating the treatment before the flower buds break open, if springtime conditions are wet and cold. Cultivars such as ‘Frost,’ ‘Muir,’ and ‘Redhaven’ are relatively resistant to peach leaf curl.

Crown and Root Rot

Fungi in the family Phytophthora cause crown and root rot in peach trees. Trees infected with the disease will slowly go into decline and it may take several years for the tree to die. The disease affects all portions of the tree with stunted growth, dieback of branches and new shoots, stunted leaves and fruits. The fungi can live for years in the soil and thrive in wet conditions where it infects the peach tree, usually through wounds in the wet bark.

There is no cure for the peach tree once infected. Prevention consists of making sure to plant the tree in an area that doesn’t retain water and drains well. If the area has a tendency to retain water and there’s no other place in the landscape to plant, create a mound that is several feet high to lift the peach tree out of the wet conditions. Keeping an area around the tree free of unwanted vegetative growth, cuts down on possible injury to the bark by lawn equipment bumping into it.

Bacterial Diseases

Several bacterial diseases affect peach trees and, depending on the bacterium and severity of the infections, the tree can eventually die.

Bacterial Leaf Spot

Peach trees suffering from bacterial leaf spot are infected with the bacterium Zanthomonas campestris pv. pruni and the bacterium affect all portions of the tree. The disease begins its infection during late winter when conditions are wet, warm, and humid. It overwinters in wounds in the bark and when conditions are windy or dew is heavy, the bacterium becomes transferred to other portions of the tree.

Symptoms first show up as tiny, water-soaked areas that are gray in color on the underside of leaves. As the disease progresses, the spotted areas become angular and change to purplish-black, with the centers then falling out. Foliage then yellows and drops from the tree, causing severe defoliation. Infected twigs develop cankers and die. Fruit infected with the bacterium develops spotting and pits, which eventually ooze and turn black.

The best course of prevention is to maintain a healthy peach tree by planting in the proper location, regular fertilization, pruning to allow adequate circulation of air, and not wounding the tree with lawn equipment. There are peach cultivars resistant to the disease such as ‘Elberta,’ ‘Jersey Queen,’ ‘Sunhaven,’ and ‘Belle of Georgia.’ Spraying trees annually while in the dormant stage with a copper or captan fungicide also helps in preventing the disease.

Crown Gall

Also called plant canker, the soil-born bacterium Agrobacterium tumefaciens causes the problem in peach trees and can live in the soil for years. The galls show on the tree as tumor-like, woody growths that are typically soft and spongy, but as they age, become hardy and crack. The galls are usually attached to the main stem of the tree and close to the ground. Sometimes they attach to the root system. The bacteria enter the peach tree’s root system through wounds.

There is no treatment for trees infected with galls. Prevent the problem by purchasing disease-free trees, not wounding the tree or roots when planting or while growing in the planting site, and keeping the tree healthy. Younger peach trees are more susceptible to the problem than older ones. If the tree dies, do not plant another in the same location.

Problems Caused by Insects

Insects transmit several serious diseases to peach trees and the only option is removing and destroying the tree.

Phony Peach Disease

The bacterium Xylella fastidiosa infect peach trees and causes phony peach disease. Sharpshooter leafhoppers infect the tree with the disease though sometimes wounds during grafting cause infection. It can take almost two years before signs of the problem show on the tree and there isn’t a cure. Signs of infection are stunted growth with a flattened canopy, early flowering and fruiting, with smaller fruit and a reduced harvest, and foliage remains attached to the tree later in fall. Infected young peach trees that haven’t produced fruit will never bear a crop. The disease doesn’t kill the tree outright, but as it progresses, the wood becomes brittle and easily breaks.

Don’t replant a peach tree in the same location where the disease has been problematic. Prevent the problem by keeping grass and weeds away from the planting site as this is where sharpshooters reside. Remove and destroy all trees infected with the disease.

Peach Yellows

A disease spread by the plum leafhopper and sometimes through improper grafting techniques. Peach yellows is not a common disease in peaches and plums are more susceptible to the problem. Peaches infected with the disease can take up to three years to show any symptoms. Signs of infection show by the foliage prematurely leafing out, and fruit ripening early. The peaches are bitter to taste and varieties that are red in color are brighter than usual. Eventually, the leaves droop and fold upward. There is no cure for the disease and the option is to remove the peach tree and destroy. Keeping the area free of weed and grass growth might help keep down leafhopper populations.

Peach Mosaic

The peach bud mite and poor grafting techniques transmit the viral disease peach mosaic. Symptoms of infection include delayed leafing out of the peach tree, small foliage is misshapen, yellow and crinkled in appearance, and inner branches are very short. The mite feeds on developing buds causing them to be misshaped. There is a reduced production of fruit, with what forms being small, covered in bumps and deformed. It’s thought the mite is transferred to the peach tree through wind. There is no cure for the disease and gardeners have no choice but to remove and destroy the tree.

Japanese Beetles

Japanese beetles are notorious for eating away the leaves and sometimes the fruit. These beetles appear in June or July in most temperate climates and have a brown body a little smaller than a dime with a sort of iridescent green shimmer to the body. They can weaken peach trees by eating away the leaves, reducing the tree’s ability to make food through photosynthesis.

Since Japanese beetles attract more beetles, gardeners have several options of control. If you don’t want to use an insecticide, handpick the beetles from the peach tree and drop them into a bucket of soapy water. Spraying the entire tree with product containing carbaryl kills the beetle. Repeat the treatment every two weeks.

Some horticulturists warn against Japanese beetle traps and claim the pheromones, or chemical smells from the traps, actually attract more beetles than would normally visit the orchard. Hanging traps far away from the orchard to draw insects away may help keep them away from trees and avoid the attraction problem.

Keep Your Peaches Happy and Healthy

Keeping your peach trees healthy starts with making sure you meet all their requirements for proper growth. If you suspect the tree is showing signs of a problem, early diagnosis and treatment is always best. Keep the tree healthy through proper fertilization, pruning, and proper spacing to allow adequate air circulation, follow a proper spraying regime, and maintain a sanitized growing site for prevention.

Beautiful, fragrant flowers in the spring, followed by sweet, luscious fruit in the summer: just two of the joys of growing a peach tree. These popular stone fruits can be grown in USDA Zones 5 through 8, but they’re happiest in the moderate temperatures of Zones 6 and 7.

Plant your peach tree in a sunny spot with loamy, well-drained soil, and keep it well watered, fertilized, and pruned to encourage the largest harvests.

For the healthiest peach trees, you’ll need to start with a cultivar suited to the average hours of winter chill in your area; all varieties of peaches require sustained temperatures of 45 degrees or less during the winter to stimulate flowering and fruit production in the spring. While most need 500 or more hours of chill, there are a few varieties that do well with as little as 100 chill hours.

But no matter how well you care for your tree, you’ll need to be on the lookout for the many peach tree diseases and pests that plague these plants. Here are some of the most common peach issues you may face.

Peach Tree Leaf Curl

Probably the most common peach tree fungus is Taphrina deformans, which causes peach tree leaf curl, sometimes referred to simply as leaf curl. This frustrating disease stunts the tree’s growth and severely hampers fruit production. It’s hard to miss the signs of this fungal infection, which also attacks nectarines. New growth in the spring first turns red, with the leaves thickening and puckering into curls. As the disease progresses, the foliage turns yellow or gray and eventually falls from the tree. Although healthy growth often replaces the fallen diseased leaves, the energy the tree uses to produce the second set of foliage tends to reduce the amount of fruit for the season.

The most effective peach tree leaf curl treatment is proactively spraying peach trees with a fungicide after the tree drops its leaves in the fall and goes dormant. Depending on where you live, this can be as early as November or as late as January. You’ll need to repeat the treatment annually to prevent reoccurrence of the infection.

You can also greatly reduce the odds of your trees becoming infected with leaf curl by initially choosing varieties that are resistant to the peach tree fungus. Pruning away any infected leaves as soon as you spot them also helps reduce the spread of this common and persistent fungus, but generally it will return the following spring, especially if conditions remain damp and cool.

Learn more about leaf curl on fruit trees.

View photos

Other Peach Tree Fungal Diseases

Peach tree fungus isn’t limited to leaf curl. Two other common fungal peach diseases are:

  • Peach scab, caused by Cladosporium carpophilu. This fungal disease, which thrives in warm, humid climates, causes the fruit to crack and rot.
  • Brown rot, which is an infection of Monilinia fructicola, turns peaches from tasty fruit into dried, withered, brown “mummies” clinging to the tree.

You can slow the spread of both conditions by removing diseased foliage, fruit, and twigs at the first sign of infection, as well as spraying the peach trees with fungicide once or twice during the growing season.

Life Cycle of a Peach Tree Borer

While there are other peach tree pests, including leafhoppers, white peach scale, mites, and aphids, none of these is as big a problem as the peach tree borer. This troublesome insect—its scientific name is Synanthedon exitiosa—is not only fond of peaches, however. It also infests other stone fruits, including plums, cherries, apricots, and nectarines.

It’s not the adult peach tree borer, which resembles a wasp, that causes trouble. It’s the creamy-white larvae that create havoc in your backyard orchard. After mating in mid- to late summer, the female peach tree borer lays her red eggs on the bark of the tree. The eggs hatch within a week or two, and the larvae chew their way into the heart of the peach tree, making use of any existing cracks in bark and generally staying close to the soil line. The hungry larvae continue to feed inside the tree until winter, which they spend underground on the tree’s roots. At the return of warm weather, the developing larvae feed even more voraciously, causing more damage before transforming into their pupal form in the early summer. The peach tree pests emerge as adults around a month later, starting the entire cycle over again.

Story continues

Get more tips on eliminating borers from your garden.

Signs of Peach Tree Borer Infestation

One of the early signs of a peach tree borer infestation is a reddish, lumpy, sticky mass around the base of the peach tree’s trunk. This messy substance is a mixture of sap, sawdust, and frass, which is insect droppings. You may also spot smaller holes in the lower tree trunk oozing clear sap.

As the insects continue to damage the living tissues underneath the tree bark, it becomes more and more difficult for water and nutrients to travel from the tree’s roots up into its leaves. Eventually, a heavily infested tree will wilt, lose leaves, or even die. Predictably, fruit production is greatly reduced in these peach trees.

Peach Tree Borer Treatment

The most effective peach tree borer treatment is insecticidal spray applied to kill larvae before they penetrate the tree bark. This means you’ll need to spray the lower portion of your peach trees no later than the first week of July, and generally once again in early August. Spray heavily infested trees a third time in late August.

Insecticides with permethrin or carbaryl as the active ingredient generally work very well to kill peach tree borer larvae and have good residual action to continue killing the pests as they hatch. When spraying peach trees for these insect pests, wet the lower portion of the trunk until the pesticide runs down to the ground. This forces the larvae to crawl through the insecticide as they chew into the bark.

Knowing the signs and treatments for common peach tree diseases will help you keep your backyard orchard growing healthy and strong.

See how to pot a fruit tree yourself.

Peach Scab (Fig. 1)
Caused by Cladosporium carpophylium
Peach scab affects peaches and nectarines in all areas of the state, causing small brown spots with a green halo on the fruit skin. Chemical or organic fungicide applications are recommended from fruit set through harvest to control peach scab. However, the earliest peach and nectarine cultivars ripen before lesions are very noticeable. 1

Fig. 2 Fig. 3

Fig. 2. C. carpophilum lesions formed on peach twig
Fig. 3. Peach scab lesions on young fruit, showing sunken, dark green, imperfect circles where spores are located
Further Reading
Peach Scab, University of Florida pdf 6 pages
Brown Rot (Fig. 4)
Caused by Monilinia fruticola (G. Wint.)
This disease is usually not a problem in central and southern Florida, because April and May are normally dry months. Fruit are harvested by late May in central and southern Florida, thus infections on the fruit are not as large a concern as in northern regions. 6

Fig. 5 Fig. 6 Fig. 7
Fig. 8 Fig. 9 Fig. 10

Fig. 11

Fig. 5. Brown rot (M. fructicola) (G. Wint.) Honey. Sporulation on rotted fruit
Fig. 9,10. Fruiting bodies
Bacterial spot (Fig. 12)
Caused by Xanthomonas arboricola pv. pruni Smith 1903 Vauterin, Hoste, Kerstters & Swings 1995 = Xanthomonas campestris pv. pruni Smith 1903 Dye 1978.
Bacterial spot can be serious on ‘Flordaprince’ and ‘Tropicbeauty’ peaches in some years, and it is difficult to control. Growing peach and nectarine varieties with resistance to bacterial spot is the best control measure, and many of the recently released cultivars have good resistance to bacterial spot. Well-fertilized trees are less susceptible to bacterial spot than underfertilized trees. 1

Fig. 13 Fig. 14 Fig. 15

Fig. 13. Bacterial leaf spot on peach
Fig. 14. Bacterial leaf spot on leaves
Fig. 15. Detail of a peach leaf cv. Maria Serena affected with spots

Peach Leaf Rust (Fig. 16)
(Tranzschelia spp.)
Peach leaf rust is of the more serious diseases in Central Florida. Severe defoliation can occur by midsummer in some instances and undoubtedly weakens the trees. Early fall defoliation can result in off-season bloom during fall and winter, which reduces yield the following spring. In North Florida, infection usually does not appear until late summer or fall, as it does in Georgia and South Carolina, where the disease is considered to be of minor importance. 1

Fig. 17 Fig. 18

Further Reading
Peach Rust (Transchelia spp.), University of Florida pdf 5 pages
Peach Rust Caused by Tranzschelia discolor in California, University of California pdf 9 pages
Mushroom Root Rot (Fig. 19)
Caused by Armillaria tabescens and A. mellea
Mushroom root rot is a fungal disease often present in newly cleared areas where oak and hickory were growing. This fungus has high incidences where peaches are planted on old pecan and tung nut land. There is no practical control, other than planting on sites relatively free of decaying oak or other hardwood roots. Rootstocks with good resistance to Armillaria are being developed. A recent release, ‘MP-29’, is available through major peach nurseries. Symptoms of Armillaria infection include sudden wilting, usually starting about the third year in the orchard. Cutting through the bark at and just below the ground line discloses a thin, white mat of fungal growth between the bark and wood. This white growth may be visible on only one side of the tree or may completely encircle the tree. Fungi may also appear. 1

Fig. 20 Fig. 21

Fig. 22

Fig. 21,22. Parasitic and/or saprobic on hardwood roots. Prolific late summer and early fall mushroom popping up in lawns and on forest floors in tight clusters that share a basal anchor to the ground which connects to hardwood roots underground. A. tabescens synonym. Note insect larvae in gills.
Further Reading
Armillaria Root Rot, University of Florida pdf 4 pages
Phony Peach
Caused by the Xylella fastidiosa bacterium
Phony Peach is a systemic disease caused by a xylem-limited bacterium, Xylella fastidiosa, it occurs in all established peach-growing areas in Florida. It is introduced in nursery stocks, in infected budwood, or from wild hosts. The phony peach bacterium is found in wild plum trees in Florida, but causes no observable damage to these plums. When transmitted to the peach by leafhoppers, it causes tree dwarfing, distorted small fruit, and poor fruit production. Before planting peaches, remove or kill all wild plums within a quarter mile of the orchard if possible. If peaches or nectarines are being propagated and budded onto rootstock, use T-budding rather than chip budding. Avoid using buds that contain woody material to limit transmission of the xylem-limited bacteria associated with phony peach disease. The acquisition of the X. fastidiosa bacteria appears to have no effect on the insect vector. 1
The bacterium X. fastidiosa is spread primarily by a type of leafhopper known as sharpshooters. The major insect vector in the coastal plain of the southeastern U.S. is probably the glassy-winged sharpshooter, Homalodisca vitripennis (Fig. 23), but other xylem-feeding insects including froghoppers and spittlebugs are considered to be potential vectors. Other leafhopper vectors include H. insolita, Oncometopia spp., Graphocephala spp. (Fig. 24) and Draeculacephala spp. 2
Further Reading
Xylella Fastidiosa Diseases and Their Leafhopper Vectors, University of Florida pdf 6 pages
Fungal Gummosis (Fig. 25)
Caused by Botryosphaeria dothidea
The fungus Botryosphaeria dothidea causes the disease peach fungal gummosis (PFG), a vascular disease that limits the growth and yield of peach orchards in the southeastern United States (Reilly and Okie 1982). Additional species of Botryosphaeria, including B. rhodina and B. obtusa, have also been associated with gumming and dieback symptoms on peaches in the United States. 3
The disease gets its name from the large amount of gum oozing from diseased tissue. The disease causes a general decline of infected trees and is often confused with mechanical injury, insect borers, and other tree diseases. The earliest symptom appears on young bark as small spots with oozing resin, generally centered on a lenticel.
“Flordadawn’, Gulfcrimson and Gulfking’ cultivars have a high susceptibility to the disease. 3
Further Reading
Fungal Gummosis in Peach, University of Florida pdf
Bacterial Canker (Fig. 26)
Caused by Pseudomonas syringae pv. syringae van Hall 1902

Fig. 27 Fig. 28 Fig. 29

Fig. 30

Fig. 27,28,29. Bacterial canker peeled to show discoloration
Crown Gall (Fig. 31)
Caused by a soil bacterium Rhizobium radiobacter
(Common name: Agrobacterium tumefaciens)

Fig. 32 Fig. 33

Fig. 34

Cytospora Canker (Fig. 35)
Caused by Leucocytospora cincta (Sacc.) Hohn. (syn. Cytospora cincta Sacc.) and Leucocytospora leucostoma, Sacc. (syn. Cytospora leucostoma Sacc.)

Fig. 36 Fig. 37

Fig. 38

Peach Tree Short Life
In the southeastern United States, peach tree short life (PTSL) refers to the sudden spring collapse and death of young peach trees. Generally, trees 3 to 7 years old are affected. PTSL is not caused by a single specific factor, but rather by a complex of cold damage and bacterial canker, caused by Pseudomonas syringae pv. syringae, which act together in some years and independently in other years. In any case, the final result is the same (i.e., tree death). 4
Phomosis Twig Blight and Fruit Rot (Fig. 39)
Superficially, Phomopsis twig blight can be confused with other causes of twig death (e.g., Cytospora canker), but can be distinguished by close examination of the canker and by laboratory culture. Cytospora spp. and Botrysphaeria spp. often invade cankers and shoots killed by Phomopsis infection.
There is considerable confusion in the literature concerning the etiology of Phomopsis twig blight and its relationship to several other canker and blight diseases of peach, including constriction canker and fusicoccum canker. However, consensus suggests the three diseases are identical. 5

Fig. 40 Fig. 41

Further Reading
Peach Leaf Curl, University of California pdf
Stone Fruit Disease Management, University of Florida ext link
Peach Diseases Research, University of Georgia ext link

Peach Tree Diseases and Pests

Beautiful, fragrant flowers in the spring, followed by sweet, luscious fruit in the summer: just two of the joys of growing a peach tree. These popular stone fruits can be grown in USDA Zones 5 through 8, but they’re happiest in the moderate temperatures of Zones 6 and 7.

Plant your peach tree in a sunny spot with loamy, well-drained soil, and keep it well watered, fertilized, and pruned to encourage the largest harvests.

For the healthiest peach trees, you’ll need to start with a cultivar suited to the average hours of winter chill in your area; all varieties of peaches require sustained temperatures of 45 degrees or less during the winter to stimulate flowering and fruit production in the spring. While most need 500 or more hours of chill, there are a few varieties that do well with as little as 100 chill hours.

But no matter how well you care for your tree, you’ll need to be on the lookout for the many peach tree diseases and pests that plague these plants. Here are some of the most common peach issues you may face.

Peach Tree Leaf Curl

Probably the most common peach tree fungus is Taphrina deformans, which causes peach tree leaf curl, sometimes referred to simply as leaf curl. This frustrating disease stunts the tree’s growth and severely hampers fruit production. It’s hard to miss the signs of this fungal infection, which also attacks nectarines. New growth in the spring first turns red, with the leaves thickening and puckering into curls. As the disease progresses, the foliage turns yellow or gray and eventually falls from the tree. Although healthy growth often replaces the fallen diseased leaves, the energy the tree uses to produce the second set of foliage tends to reduce the amount of fruit for the season.

The most effective peach tree leaf curl treatment is proactively spraying peach trees with a fungicide after the tree drops its leaves in the fall and goes dormant. Depending on where you live, this can be as early as November or as late as January. You’ll need to repeat the treatment annually to prevent reoccurrence of the infection.

You can also greatly reduce the odds of your trees becoming infected with leaf curl by initially choosing varieties that are resistant to the peach tree fungus. Pruning away any infected leaves as soon as you spot them also helps reduce the spread of this common and persistent fungus, but generally it will return the following spring, especially if conditions remain damp and cool.

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Other Peach Tree Fungal Diseases

Peach tree fungus isn’t limited to leaf curl. Two other common fungal peach diseases are:

  • Peach scab, caused by Cladosporium carpophilu. This fungal disease, which thrives in warm, humid climates, causes the fruit to crack and rot.
  • Brown rot, which is an infection of Monilinia fructicola, turns peaches from tasty fruit into dried, withered, brown “mummies” clinging to the tree.

You can slow the spread of both conditions by removing diseased foliage, fruit, and twigs at the first sign of infection, as well as spraying the peach trees with fungicide once or twice during the growing season.

Life Cycle of a Peach Tree Borer

While there are other peach tree pests, including leafhoppers, white peach scale, mites, and aphids, none of these is as big a problem as the peach tree borer. This troublesome insect—its scientific name is Synanthedon exitiosa—is not only fond of peaches, however. It also infests other stone fruits, including plums, cherries, apricots, and nectarines.

It’s not the adult peach tree borer, which resembles a wasp, that causes trouble. It’s the creamy-white larvae that create havoc in your backyard orchard. After mating in mid- to late summer, the female peach tree borer lays her red eggs on the bark of the tree. The eggs hatch within a week or two, and the larvae chew their way into the heart of the peach tree, making use of any existing cracks in bark and generally staying close to the soil line. The hungry larvae continue to feed inside the tree until winter, which they spend underground on the tree’s roots. At the return of warm weather, the developing larvae feed even more voraciously, causing more damage before transforming into their pupal form in the early summer. The peach tree pests emerge as adults around a month later, starting the entire cycle over again.

Signs of Peach Tree Borer Infestation

One of the early signs of a peach tree borer infestation is a reddish, lumpy, sticky mass around the base of the peach tree’s trunk. This messy substance is a mixture of sap, sawdust, and frass, which is insect droppings. You may also spot smaller holes in the lower tree trunk oozing clear sap.

As the insects continue to damage the living tissues underneath the tree bark, it becomes more and more difficult for water and nutrients to travel from the tree’s roots up into its leaves. Eventually, a heavily infested tree will wilt, lose leaves, or even die. Predictably, fruit production is greatly reduced in these peach trees.

Peach Tree Borer Treatment

The most effective peach tree borer treatment is insecticidal spray applied to kill larvae before they penetrate the tree bark. This means you’ll need to spray the lower portion of your peach trees no later than the first week of July, and generally once again in early August. Spray heavily infested trees a third time in late August.

Insecticides with permethrin or carbaryl as the active ingredient generally work very well to kill peach tree borer larvae and have good residual action to continue killing the pests as they hatch. When spraying peach trees for these insect pests, wet the lower portion of the trunk until the pesticide runs down to the ground. This forces the larvae to crawl through the insecticide as they chew into the bark.

Knowing the signs and treatments for common peach tree diseases will help you keep your backyard orchard growing healthy and strong.

  • By Michelle Ullman

Major Insect Pests of Peach in Georgia

Peachtree Borer (Synanthedon exitiosa)

Larvae are dirty-white caterpillars with brown heads, up to one inch (25 mm) long. They feed in the cambium and inner bark of trees near or just below the soil level, causing deadened areas in the bark. Damage is often first detected as masses of gum containing grass and sawdust exuding from a tree around the base of the trunk. Young trees often are completely girdled and die. Extensively damaged older trees lose vigor and productivity and tree life is generally shortened.

Oriental Fruit Moth (Grapholitha molesta)

Larvae are pinkish to creamy-white caterpillars with brown heads, about 1/2 inch (13 mm) in length. Early in the season, larvae tunnel in tender twigs causing twig die-back (flagging). Heavy infestations may give the tree a bushy appearance. Later generations may feed on terminal growth and developing peaches. Larvae attacking the fruit often enter near or through the stem and bore directly into the interior of the fruit. Larger peaches may show no external damage. Fruit damage may cause an increase in the amount of brown rot.

Life cycle diagram.

Plum Curculio (Conotrachelus nenuphar)

Adults are small, brown snout beetles, about 3/8 inch (9 mm) long, mottled with lighter gray or brown markings. Larvae are yellowish-white, legless, brown-headed grubs, up to 3/8 inch (9 mm) long. Adults damage fruit by making small circular feeding punctures or small crescent-shaped cuts following egg laying. Early-season adult damage causes scarred, malformed fruit (catfacing) and can provide entry for brown rot. Larvae tunnel and feed in developing fruit, often causing young fruit to drop. Second generation curculios may also be a problem on mid- and late-maturing peach varieties.

Sucking Bugs and Catfacing Insects

There are a number of sucking bugs affecting peaches including:

  • Tarnished Plant Bug (Lygus lineolaris)
  • Green Stink Bug (Acrosternum hilare)
  • Southern Green Stink Bug (Nezara viridula)
  • Leaffooted Bug (Leptoglossus phyllopus)
  • Euschistus spp. and others

Feeding by one or more species causes scarred, distorted fruit with sunken areas (catfacing). Such damage can occur throughout the season but most occurs during the period from just prior to bloom until the peaches are about 1/2 inch (13 mm) in diameter. Larger peaches may show signs of attack by exuding droplets or strings of gum at the feeding site, but distortion of large fruit usually is less severe.

Tarnished Plant Bug Southern Green Stink Bug Leaffooted Bug

Mites

Both European Red Mite (Panonychus ulmi) and Two-Spotted Spider Mite (Tetranychus urticae) can be problematic in peach.

These are tiny, about 1/60 inch (0.4 mm) long, colorless, brownish-red, or greenish 8-legged pests which feed on the undersides of leaves causing a whitish to yellow mottling of the leaves which may become bronzed. High populations of the two-spotted spider mite may be indicated by light webbing on leaves, twigs or fruit. Heavy mite infestations cause premature defoliation and reduce fruit size.

Two-spotted spider mite (right) and European red mite (left)

Lesser Peachtree Borer (Synanthedon pictipes)

The borers are creamy-white caterpillars with brown heads, up to 1 inch (25 mm) long and feed in inner bark of the upper trunk and large branches. Injury is similar to that caused by the peachtree borer: masses of gum exuding from deadened areas containing larvae. Damage usually is worst in forks and around wounds in the bark.

Larva Damage – gummosis

White Peach Scale (Pseudaulacapsis pentagona)

Armored female scales are inconspicuous, circular, brownish-white, convex, and about 1/12-1/10 inch (2.0-2.5 mm) in diameter. Armored males, usually found in clusters on the lower trunk and large branches, are elongated, snowy white and about 1/16 inch (1.5 mm) long. Heavy infestations weaken or kill twigs or branches and unattended trees usually die within 2 or 3 years

Leafhoppers

Among the leafhoppers that can be problematic in peach are:

  • Homalodisca coagulata
  • Oncometopia orbona
  • Graphocephala versuta
  • Homalodisca insolita
  • Cuerna costalis

These slender, rather large, often brightly colored leafhoppers (sharpshooters) feed into the xylem tissue of peach twigs. Often present in high numbers, their primary importance is as vectors of phony peach disease.

Cuerna costalis Oncometopia orbona Homalodisca coagulata
Sharpshooter Leafhopper Glassy-winged sharpshooter

Originally compiled from

  • “Insect and Disease Identification Guide for IPM in the Southeast”, The University of Georgia, Cooperative Extension Service Bulletin 849, September 1981.
State and Regional Articles General • Georgia

Purge the peach trees of pests

Question: We have two peach trees in our backyard and we have two different issues going on that keep us from seeing any ripe fruit. Can you advise us on what’s going on and how to handle it? First, there are holes in the growing peaches. When you crack one open, there’s a little worm inside. Second, there is sticky sap leaking out from a few spots at the base of both of the trees.

Answer: Peaches are among the most difficult tree fruits to grow. They’re susceptible to several different pests, in addition to a few diseases such as brown rot (which leads to rotten fruit) and peach leaf curl (which leads to contorted, discolored foliage).

Despite the challenges in growing them, homegrown peaches are well worth the effort. Their sun-ripened flavor is spectacular, and each tree’s productive life is typically between 12 and 15 years.

It sounds like you’re dealing with two very common insect-related issues peach growers face in Pennsylvania. Let’s look at each one of them.

The small holes and tiny worms you’re finding on and in the peaches themselves are likely to be codling moths. These moths attack not just peaches, but also apples, pears and quince. Female coddling moths lay eggs on developing fruit or leaves, and in a few weeks, the newly hatched larvae create tunnels inside the fruit. They often are found near the core feeding on the seeds. These tiny caterpillars then leave the fruit through a separate exit hole, drop to the ground to pupate into an adult, and start the cycle again, often producing two generations in a season.

The best preventative method for codling moths is to use pheromone traps to lure and capture the adults. These traps are hung in the trees a few weeks before the flower buds open. They need to be replaced in July to control the second hatch. Two traps per full-sized peach tree will suffice.

There are insecticides that work to control codling moths, but many of them are harmful to bees and other pollinators. One natural spray that’s quite effective in preventing codling moths from laying eggs on your peaches is kaolin clay. Kaolin clay is a mined mineral that’s used in everything from toothpaste to antacids.

Sprayed on the fruit as a liquid, this wettable powder dries to form a thin, powdery coating on the fruit, repelling the adult moths and preventing them from laying their eggs. Begin spraying the tree at petal drop and continue to do so every 7-10 days for about eight applications. The trees look a little funny coated in the white spray, but it’s worth it.

Your second issue sounds much like peach tree borers. The larvae of a different species of moth, peach tree borers attack not only peach trees, but also plums, cherries, nectarines and apricots.

Adult moths lay eggs on the bark of the tree in mid- to late summer. The newly hatched larvae burrow under the bark, tunneling between the inner bark and the sap wood, causing the tree to lose vigor. If there are multiple borers per tree, it can cause decline and eventual death. The globs of sticky sap you see leak out of their entrance holes throughout the growing season. The larvae overwinter in the tree, then emerge from an exit hole as adults early the following summer.

Pheromone traps are useful to capture and monitor adult peach tree borers. But the best method for controlling the borer is to carefully examine the tree trunk for small holes with bits of sawdust coming out of them every fall. If you find an entrance hole, push a piece of straightened wire in, as far as it will go, to squash the borer.

Another option is to inject a specific species of beneficial nematodes (Steinernema carpocapsae) into the hole using a needleless syringe. The USDA’s Agricultural Research Service found that an application of nematodes was able to control peach tree borers as well as synthetic chemical applications in small field trials.

  • Horticulturist Jessica Walliser is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is jessicawalliser.com. Send your gardening or landscaping questions to or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.

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