How to Manage Pests

Pests in Gardens and Landscapes

Peach Leaf Curl

Revised 5/12

In this Guideline:



  • Identification and damage
  • Life cycle
  • Management
  • About Pest Notes
  • Publication
  • Glossary


Peach leaf curl symptoms typical of a serious infection.
Peach leaf curl symptoms can cause leaves to curl and distort.
Though uncommon, symptoms on fruit can occur, making the surface corky and cracked.

Peach leaf curl, also known as leaf curl, is a disease caused by the fungus Taphrina deformans. Peach leaf curl affects the blossoms, fruit, leaves, and shoots of peaches, ornamental flowering peaches, and nectarines, and is one of the most common disease problems for backyard gardeners growing these trees. The distorted, reddened foliage that it causes is easily seen in spring. When severe, the disease can reduce fruit production substantially.

IDENTIFICATION AND DAMAGE

Peach leaf curl first appears in spring as reddish areas on developing leaves. These areas become thickened and puckered, causing leaves to curl and severely distort. The thickened areas turn yellowish and then grayish white, as velvety spores are produced on the surface by the leaf curl fungus. Later affected leaves turn yellow or brown and can remain on the tree or may fall off; they are replaced by a second set of leaves that develop more normally unless wet weather continues. The loss of leaves and the production of a second set result in decreased tree growth and fruit production. Defoliation in spring may expose branches to sunburn injury.

The peach leaf curl pathogen also infects young green twigs and shoots. Affected shoots become thickened, stunted, distorted, and often die. Only rarely do reddish, wrinkled to distorted (or hypertrophied) areas develop on fruit surfaces. Later in the season these infected areas of fruit become corky and tend to crack. If leaf curl infection builds up and is left uncontrolled for several years, the tree may decline and need to be removed.

LIFE CYCLE

Leaf symptoms appear about 2 weeks after leaves emerge from buds. The fungus grows between leaf cells and stimulates them to divide and grow larger than normal, causing swelling and distortion of the leaf. Red plant pigments accumulate in the distorted cells. Cells of the fungus break through the cuticle of distorted leaves and produce elongated, sac-like structures called asci that produce sexual spores called ascospores, which give the leaf a grayish white, powdery or velvetlike appearance. The ascospores are released into the air, carried to new tissues, and bud (divide) to form bud-conidia.

The fungus survives the hot, dry summer as ascospores and bud-conidia (asexual spores) on the tree’s surfaces. When the weather turns cool and wet in fall, the ascospores germinate to produce more bud-conidia. The new and old bud-conidia continue to increase in number by budding. Eventually a film of bud-conidia is formed on the tree’s surface. In spring, the bud-conidia move by splashing water from irrigation or rain and can infect new leaves.

Periods of cool, wet weather, when leaves are first opening on the tree, favor the disease. The optimum temperature for fungal growth in laboratory cultures is 68°F, the minimum is 48°F, and the maximum is 79° to 87° F. Budding of bud-conidia occurs at or above 95% relative humidity. Wetness from rain, dew, or irrigation for more than 12.5 hours at temperatures below 61°F is needed for infection. Maximum infection occurs when trees are wet for 2 or more days. Although leaves can be infected, symptoms might not appear if temperatures remain above 69°F. Cool weather prolongs the period of disease development by favoring the pathogen and slowing leaf growth. Development of peach leaf curl ceases when young tissue is no longer developing or when weather turns dry and warmer (79° to 87°F).

MANAGEMENT

To prevent peach leaf curl, use resistant peach and nectarine varieties where possible. (See the Resistant Varieties section below.) For nonresistant varieties, treat trees with a fungicide every year after leaves have fallen. In cooler northern locations leaf fall usually is in late November. In warmer southern locations leaf fall can be as late as early January. Generally a single early treatment when the tree is dormant is effective, although in areas of high rainfall or during a particularly wet winter, it might be advisable to apply a second spray late in the dormant season, preferably as flower buds begin to swell but before green leaf tips are first visible.

Resistant Varieties

A few peach varieties are available that are resistant or partially resistant to leaf curl. Currently available resistant varieties include Frost, Indian Free, Muir, and Q-1-8.

The peach cultivar Frost is reportedly very tolerant but must receive fungicide applications the first 2 to 3 years. Redhaven peach and most cultivars derived from it are tolerant to peach leaf curl, whereas Redskin peach and cultivars derived from it range from susceptible to highly susceptible to the disease.

There are fewer resistant nectarines, although Kreibich is one such variety.

Fungicides
Copper

Historically, the most commonly used fungicides available to home gardeners have been the fixed copper products. For all copper-containing products, the active ingredient, copper, is listed as “metallic copper equivalent,” or MCE, on the label. Various product formulations differ widely in their metallic copper content. The higher the MCE, the greater the amount of copper and the more effective the product will be. However, other factors such as coverage, use of additives as such stickers and spreaders, and frequency and duration of rain, which can wash off the copper, also will impact product effectiveness. In all cases, the copper is active only when it is wet, when the copper ions are in solution.

Fixed copper products include tribasic or basic copper sulfate, cupric hydroxide, and copper oxychloride sulfate (C-O-C-S), but currently only liquid products containing copper ammonium complex products with 8% MCE (e.g., Kop R Spray Concentrate and Liqui-Cop ) are available to consumers. The most effective copper product, 90% tribasic copper sulfate with a 50% MCE (Microcop), is no longer available to retail outlets, because the manufacturer withdrew the product in 2010, although remaining supplies still can be sold.

The copper ammonium complex products can be made more effective by adding 1% horticultural spray oil to the application mix; the oil also aids in controlling some aphids, scale insects, and mites. Copper soap (copper octanoate) fungicides are also available, and preliminary research indicates they may provide some protection of trees.

Be aware that repeated annual use of copper products over many seasons can result in a buildup of copper in the soil, which eventually can become toxic to soil organisms, and if it moves into waterways, can harm some aquatic species.

Bordeaux Mixture

Copper sulfate is not a fixed copper and, when used alone, is less effective than tribasic copper sulfate or other fixed copper products. However, if copper sulfate is mixed with hydrated lime to make a Bordeaux mixture, the copper sulfate and calcium in the lime react together to form a fixed copper product that is effective against peach leaf curl. Bordeaux mixture is not available for sale; it must be mixed up just before application, and the ingredients can be very difficult to find. For information on preparing Bordeaux mixture see Pest Notes: Bordeaux Mixture.

Other Fungicides

The synthetic fungicide chlorothalonil currently is the only other noncopper fungicide available for managing peach leaf curl on backyard trees. Lime sulfur (calcium polysulfide) products no longer are registered for backyard use.

Application

Thorough coverage with any fungicide is essential to obtain adequate disease control. Trees should be sprayed to the point of runoff or until they are dripping.

When using pesticides, always read and follow the label for usage, rates, toxicity, and proper disposal. Proper protective clothing and gear including goggles should be used when handling any pesticides.

Physical Controls

Although symptoms of leaf curl are seen primarily in spring as new leaves develop, there is little you can do to control the disease at this time. Some people remove diseased leaves or prune infected shoots, but this has not been shown to improve control. Normally, diseased leaves fall off within a few weeks and are replaced by new, healthy leaves, unless it is rainy.

If a tree is severely affected with peach leaf curl this can stunt its growth, so consider thinning fruit later in the season. Pruning in fall prior to applying any fungicides can reduce spore numbers overwintering on the tree and reduce the amount of fungicide needed. If leaf curl symptoms occurred on your trees in spring, be sure to treat the following fall and/or winter to prevent more serious losses the following year.

WARNING ON THE USE OF PESTICIDES

Broome, J. C. and D. R. Donaldson. June 2010. Pest Notes: Bordeaux Mixture. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 7481.

McCain, A. H. 1978. Peach leaf curl control for home gardeners in the San Francisco Bay Area. Calif. Plant Pathol. 43:4–5.

McCain, A. H., E. J. Perry, and G. W. Hickman. 1979. Leaf curl fungicides. Calif. Plant Pathol. 46:1–2.

Ogawa, J. M., E. I. Zehr, G. W. Bird, D. F. Ritchie, K. Uriu, and J. K. Uyemoto. 1995. Compendium of Stone Fruit Diseases. APS Press, St Paul, Minn.

Rossi, V., M. Bolognesi, L. Languasco, and S. Giosue. 2006. Influence of environmental conditions on infection of peach shoots by Taphrina deformans. Phytopathology 96:155–163.

PUBLICATION INFORMATION

Pest Notes: Peach Leaf Curl
UC ANR Publication 7426

Produced by UC Statewide IPM Program, University of California, Davis, CA 95616

PDF: To display a PDF document, you may need to use a PDF reader.

Top of page

Peach leaf curl

Airborne fungal spores land on buds to infest newly-emerging leaves in spring. The fungus feeds on the young leaves and affects their development so that they become distorted. The smaller leaf size makes them less efficient at making food for the plant and in its weakened state, the flowers and fruit fall off. Trees may recover sufficiently to make a second flush of growth and these leaves are usually unaffected by the fungus. Fungus survives on fallen leaves and branches to re-infect next season’s buds.

Advertisement

Symptoms

Distorted and puckered peach tree leaves, which may have a bronzed or reddish colour. Flowers and fruit may fall prematurely and death of the tree may eventually result.

Find it on

peach, nectarine, apricot and almond trees

Advertisement

Organic

Remove any infected leaves as soon as they are seen, together with flowers and fruit. Clear up infected, fallen leaves around trees. Cover fence or wall-trained trees with polythene sheet in January and February to prevent development of fungus. Alternatively, erect an open-sided ‘tent’ over bushes in the open garden. Mulch around the base of trees with garden compost to maintain general health, and water well in dry summer weather. Avoid over-feeding with nitrogen fertiliser.

Note Number: AG0160
Published: December 1999
Updated: August 2010

Leaf curl, caused by the fungus Taphrina deformans, is mainly a disease of peaches and nectarines, although it may also affect almonds and apricots. The disease occurs wherever peaches and nectarines are grown, and if not controlled can seriously weaken trees.

Fig 1. Early stage of infections with pink coloured leaves.

In spring infected new leaves are thickened, curled and distorted. They are pale-green at first, but soon show red or purple colours and become conspicuous. Often the entire leaf is affected, but sometimes, especially with late infections, only small patches of the leaf are affected (Figure 1 and 2). Infected fruit show raised, irregular rough patches that are often red in colour. Such fruit often falls prematurely. Later the colour fades as the fungus begins to produce masses of powdery grey spores on the upper surface of the leaf. The diseased tissue dies and leaves may fall soon after the spores are produced. However, the tree usually produces new leaves that remain healthy as the season advances. If cool, wet weather persists during spring, infections may continue to appear on new leaves for several months. Infected shoots are thickened, distorted and yellow-green in colour. Heavily infected shoots may be killed.

Economic importance

If uncontrolled, leaf curl is most destructive. It may destroy the new leaves in spring, cause shoot dieback and loss of crop. If unchecked over several years, the disease may gradually weaken the tree until it dies.

Disease cycle

Cool, wet conditions during leaf emergence in spring favour the development of leaf curl. Continued cool, wet weather favours further cycles of the disease. Disease development is stopped by high summer temperatures and the fungus survives summer as ascospores. These germinate in autumn rains and form yeast-like spores that can overwinter in bud-scales and on twigs. These spores then infect the newly developing leaves that are produced from such buds in spring.

Control

Fig 2. Infections become thicker and distorted on mature leaves

Leaf curl can usually be controlled satisfactorily by one spray of a suitable registered fungicide at any stage of dormancy. Most effective control is achieved by spraying when the buds are swelling but before they have opened. It is not possible to control the fungus once it has entered the leaf. Poor disease control is usually a result of spraying too late; that is, after budswell. In a planting containing peach and nectarine cultivars, sprays must be timed for that cultivar which shows the earliest movement of buds.

Where the disease has been difficult to control in previous seasons, a program of three sprays is recommended. The first spray should be applied in autumn, at leaf fall. The second spray should be applied immediately before budswell at the late dormant stage, and the third spray about one week later at budswell.

Some cultivars show resistance to leaf curl, but apparent resistance observed in the field may be due to different times of bud movement which may avoid favourable conditions in one season, only to become infected in another season following different weather conditions.

Contacts/services available from DEPI

For effective pest and disease control, correct diagnosis is essential. Phone Crop Health Services on (03) 9032 7515 or fax (03) 9032 7604

Acknowledgements

This Agriculture Note was first published in December 1999 and it was most recently reviewed by W.S. Washington, Plant Standards in August 2010.

ISSN 1329-8062

Published and Authorised by:
Department of Environment and Primary Industries
1 Spring Street
Melbourne, Victoria

This publication is copyright. No part may be reproduced by any process except in accordance with the provisions of the Copyright Act 1968.

The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication

Treat peach leaf curl now

The warm weather forecast for this week and next, with highs forecast in the 70s and lows near 50, means that fruit trees will begin growth and grow rapidly. We may be several weeks ahead of normal by the next spring freeze which looks to be a week or more away. Growers need to get out their early disease control sprays.


Peach leaf curl symptoms showing both red, crinkled leaves and thick, spore-covered leaves.

For peach growers, the first spray of the year is to control “curl leaf” or peach leaf curl. Peach leaf curl is an important disease in Michigan. This disease can defoliate peach and nectarine trees. The fungus that causes peach leaf curl overwinters on the tree. Infections take place in the spring as the buds open. The fungus infects peach buds from bud swell to bud opening under wet conditions. Air temperatures between 50 to 70°F are ideal. Rain or dew moves spores into the opening buds, allowing the infection of young tissue. The disease requires about 10 to 11 hours of wetness for infection to occur. Prolonged cool wet periods during bud burst can result in severe infections. Early spring applications at or before bud break are effective in controlling this disease.

Effective controls include Bravo, Ziram, Carbamate and copper compounds. Most growers try to use copper early. If you believe an infection may have already occurred, you are better off using Bravo or Ziram rather than copper because these materials are more effective after infection. Later applications can reduce the severity of the disease. Copper compounds have the added benefit of providing some suppression of bacterial spot as well. (See Bill Shane’s article on copper compounds used on fruit). If you are going to use copper, be sure to use the rate of 4 to 8 pounds of metallic copper per acre. Some product labels may recommend less and some Michigan growers have been disappointed with lower rates. Peach growers in Berrien County, Mich., are already putting on their copper sprays now.

Once leaves are infected there is no effective fungicide treatment. The leaves are infected in the bud; once they have emerged they are no longer susceptible to infection. Infected leaves become crinkled, turning orange or red. The leaves become thick and powdery with spores as the fungus sporulates. Infected leaves eventually fall off. The tree will grow new leaves.

Peach leaf curl weakens the tree by removing leaves during early growth. This reduces energy the tree can absorb from the sun, weakening the tree, and reduces growth and fruit size. Heavy fruit thinning reduces stress on the tree and increases the likelihood of a marketable crop. Severely infected trees should receive an increased ration of nitrogen fertilizer. This will help the tree replace lost leaves and maintain vigor.

Peach, Apricot, and Nectarine

Armillaria Root Rot: This can be a major disease in older orchards and replanted orchards. (See Photo) (See Section on Mushroom Root Rot)

Bacterial Canker (bacterium – Pseudomonas syringae): Elongated cankers develop at the base of buds and randomly on the trunk and scaffold limbs (See Photo). Damaged areas are slightly sunken and somewhat darker in color than the surrounding bark. At both the upper and lower margins of the canker, narrow brown streaks extend into healthy tissue. As the trees break dormancy in the spring, gum is formed by the surrounding tissue and may exert enough pressure to break through the bark and flow. The area beneath the canker has a soured odor. Individual scaffolds or the entire tree usually dies shortly after leafing out in the spring. Roots are not affected. Extensive suckering (See Photo) often occurs at the tree base. The bacterium is a weak pathogen and causes serious damage only when a tree is in a dormant condition or weakened due to unfavorable growing conditions. Bacterial canker is a component in a disease complex known as Peach Tree Short Life. Trees up to 7 years old, growing on deep sandy soil are most susceptible. Avoid using high nitrogen fertilizer rates in mid to late summer. Do not encourage late fall growth. Prune when the trees are fully dormant (January and February). High dosage of a copper-containing fungicide at leaf drop has been somewhat successful.

Bacterial Spot (bacterium – Xanthomonas campestris pv. pruni): Symptoms on leaves are observed first as small, circular, or irregularly shaped, pale green lesions (See Photo). During early development, lesions almost always are concentrated near the leaf tip. In advanced stages, the inner portion of the lesion falls out, giving the leaf a “ragged” or “shot hole” appearance. Leaves heavily infected with bacterial spot turn yellow and fall. Repeated infection can occur throughout the growing season as long as the environment is favorable. Symptoms first appear on fruit as small, olive brown, circular spots. Spots become slightly darker and depressed as the bacteria develops. Lesions are scattered over the fruit surface and tiny cracks develop in the center of the spots. Sometimes symptoms resemble peach scab (See Photo). Leaf infection is more common than fruit infections. Apparently, more specific climatic conditions are necessary for fruit to become infected. Chemical control during the season is difficult. Dormant sprays have been somewhat effective if the spray is timed to protect stems during the fall infection period. Copper containing fungicides should be applied just as the leaves begin to shed. Resistant varieties are available. (See Fungicide Table Below)

Brown Rot (fungus – Monilinia fructicola): The brown rot fungus causes blossom blight and fruit rot, but fruit rot is the most common. Surface moisture and moderately warm temperatures favor disease development. With blossom blight, flowers turn brown and are water-soaked. The fungus grows down the pedicel into the stem resulting in dark brown, sunken areas (See Photo). Young stems are often girdled causing twig dieback. In some instances, young fruit may become infected but not show symptoms until the fruit matures. Generally, fruit are resistant to infection during the hard green stages of development. Fruit are most susceptible near maturity. The fungus enters fruit directly or through natural openings or wounds. A brown, water-soaked lesion rapidly develops (See Photo). The brown rot fungus overwinters in mummies, stem cankers and on infected fruit peduncles. Beetles or other insects can be vectors for the fungus. Control by applying a fungicide (See Fungicide Table Below) during pink bud, bloom, petal fall, and at preharvest. Post harvest decay can be serious if fruit is not protected. Nectarines are more susceptible than peaches.

Cotton Root Rot: (See Section on Cotton Root Rot)

Crown Gall: (See Section on Crown Gall)

Fungal Gummosis (fungus – Botryosphaeria dothidea): The fungus enters through wounds or lenticels on lower parts of scaffold limbs and the trunk. Older infection sites typically exude gummy resin. Necrosis is associated with infection but usually is restricted to the area just under the bark. Over time the bark develops a rough texture. Trees can recover somewhat if infection is not severe. Stressed trees are damaged the most. (See Photo)

Leucostoma Canker (fungus – Leucostoma cinata – anamorph Cytospora leucostoma): The fungus is a weak pathogen and is rarely a problem in well managed orchards with rapidly growing trees. Pimple-like bumps develop on the surface of cankers. During the growing season small streams of gum are formed at each pimple. In most cases a callus layer forms around the damaged area and the canker is walled off. In a few cases the canker growth will resume in the fall after the callus growth is slowed. Leucostoma canker may become established in a limb through pruning cuts or sunburn injury. Affected trees should be pruned to remove the canker sites and fertilized to promote growth. (See Photo)

Leucostoma Canker (fungus – Leucostoma cinata – anamorph Cytospora leucostoma): The fungus is a weak pathogen and is rarely a problem in well managed orchards with rapidly growing trees. Pimple-like bumps develop on the surface of cankers. During the growing season small streams of gum are formed at each pimple. In most cases a callus layer forms around the damaged area and the canker is walled off. In a few cases the canker growth will resume in the fall after the callus growth is slowed. Leucostoma canker may become established in a limb through pruning cuts or sunburn injury. Affected trees should be pruned to remove the canker sites and fertilized to promote growth. (See Photo)

Oxyporus Root and Crown Rot (fungus – Oxyporus sp.): The fungus forms a thick, white to slightly off-white fungal mat at the base of tree trunks. Trees infected with Oxyporus show a slow decline. There are no specific controls.

Peach Leaf Curl (fungus – Taphrina deformans): The peach leaf curl fungus infects leaves, flowers, and fruits. Infected leaves are characterized by puckering, thickening and curling. Diseased leaves become pale yellow to light green and shed after a short time (See Photo). Fruit and blossoms shed when infected and are seldom observed by growers. Disease development is related to air temperature at the time buds are opening. If surface moisture is present and the air temperature is near 68oF, infection can take place. Temperatures above 86oF and below 40oF inhibit the fungus. After symptoms are visible, control is impossible. Apply a fungicide (See Fungicide Table Below) at the beginning of dormancy and/or just prior to bud break.

Peach Mosaic (virus): This viral disease affects peach and plum. General symptoms are delayed foliation, and small, narrow, crinkled, mottled, yellow leaves. Internodes are shortened, and lateral buds break, giving a rosette appearance. The few fruit produced are deformed resulting in bumpy, misshapen, small fruit. Spread is by grafting and the peach bud mite, Eriophyes insidiosus. Remove all virus-infected trees as soon as they are discovered.

Peach Scab (fungus – Cladosporium carpophilum): Peach scab, also known as “freckles,” is found wherever peaches are grown. It is most apparent on mid-late season varieties. Small spots develop on fruit and are normally concentrated around the stem or shoulder of the fruit (See Photo). Lesions formed on young twigs serve as a means of overwintering. Primary infection in the spring comes from spores produced in twig cankers formed the previous year. Fruit infection normally occurs after shuck split and 2-4 weeks following. Once infection occurs, 40 to 70 days may elapse before symptoms are visible. Control is by repeated applications of an approved fungicide (See Fungicide Table Below) during the critical period beginning at shuck split.

Peach Yellows (phytoplasma): The disease has been observed in Texas but is rarely found. Fruits on diseased trees ripen from a few days to three weeks prematurely, have a bitter taste, and are reduced in size. Varieties which normally have red skin are abnormally bright. Leaves are chlorotic, fold upward, and tend to droop. Infected trees leaf out prematurely. The disease is spread by grafting and feeding by the plum leafhopper Macropsis trimaculata (Fitch). After infection, it may be 40 days to three years before disease symptoms are visible. Use only bud wood from healthy trees and destroy any trees which show typical disease symptoms.

Phony Peach (bacterium – Xylella fastidiosa): This disease does not cause rapid death of trees but results in reduced growth and fruit size. Twigs on diseased trees have shortened internodes and increased lateral branching. The general appearance is a dwarfed, compact growth pattern with dark green foliage. After a few years, the wood becomes brittle and terminal dieback is common. Infected trees leaf out first in the spring and hold their foliage later in the fall. Fruit also ripens earlier on diseased trees. Disease is spread by root grafting and leafhoppers. Remove all trees showing symptoms of phony peach and destroy wild plums growing near the orchard.

Phytophthora Root Rot (fungus – Phytophthora spp.): Roots infected by this fungus show extensive root necrosis. Although Phytophthora Root Rot has not been verified in Texas, its presence is suspected based on its wide distribution. Phytophthora Root Rot is most severe on replant sites or in orchards planted on poorly drained soils.

Rhizopus Rot (fungus – Rhizopus stolonifer): This fungus is most active during warm, humid weather. Fruit infection results in a “black whiskered” appearance caused by fungal strands which produce an abundance of black spores. Rhizopus attacks peaches and plums only at maturity. Disease prevention is primarily based on orchard sanitation, preharvest fungicides, and rapid refrigeration of processed fruit. Picking containers should be such that fruit receives a minimum amount of handling. Packing equipment should cause minimum injury. Pad any area where fruit will drop onto a belt or roller.

Root Knot (Nematode – Meloidogyne spp.) Use resistant rootstocks. (See Root Knot Nematode)

Peach Rootstock and Their Reaction To Root Knot Nematode

Rootstock Root Knot (Meloidogyne spp.)
Nemaguard Resistant
Lovell Susceptible
Elberta Susceptible
Nemared Resistant (Has not been extensively evaluated in Texas)
Note: Different races exist within root knot species. Some have been shown to attack “resistant rootstocks” under greenhouse conditions.

Rust (fungus – Tranzschelia discolor): Reddish-brown pustules occur on the lower leaf surface marked by a yellow spot on the upper surface (See Photo). It causes premature defoliation which reduces tree vigor. The rust species that infects peach does not infect plum. In most parts of Texas rust is a late season disease that generally does not require treatment. (See Fungicide Table Below)

Shot Hole (fungus – Wilsonomyces carpophilus): Was formerly called Coryneum blight. Blight lesions on leaves are small, circular, purple spots. In advanced stages spots on the leaves fall out giving the leaf a ragged appearance. Defoliation seldom occurs unless infection is severe. Fruit infection is rare. Buds and twigs die if heavily infected. For most effective disease control, apply dormant sprays immediately after leaves are shed or just prior to budbreak in spring. (See Fungicide Table Below)

Waterlogging (physiological): Peach and nectarines, more so than apricots, require well drained soil for good growth. Prolonged periods of waterlogged soil depletes soil oxygen which is deadly to roots. Foliage may turn yellow and shed or develop a reddish purple color. Dead roots are deep purple to black inside and have a foul odor (See Photo). Where needed, terrace land for optimum drainage and plant on raised beds.

Fungicides for use on Prunus species

Bacterial Spot Brown Rot Peach Leaf Curl Scab Shot Hole Rhizopus Rot Rust
copper hydroxide,
ziram,
spreptomycin
sulfate
benomyl, captan,
iprodione, triforine, thiophanate methyl, propiconazole,
fenbuconazole,
tebuconazole, sulfur
chlorothalonil,
copper hydroxide,
ziram
benomyl,
captan,
chlorothalonil, thiophanate
methyl, sulfur, iprodione
chlorothalonil,
copper hydroxide
dicloran chlorothalonil,
sulfur

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.

Leave a Reply

Your email address will not be published. Required fields are marked *