Peach tree curly leaf

A fungal disease that affects peaches and nectarines, leaf curl (Taphrina deformans) is one of the most common disease problems found in backyard orchards. Symptoms appears in spring as reddish areas on developing leaves. These areas become thick and puckered causing leaves to curl and distort. When severe, leaf curl can substantially reduce fruit production.

Disease fungi overwinter as spores (conidia) underneath bark, around buds and in other protected areas. Early in the growing season, during cool, wet spring weather, the spores infect new leaves as they emerge from the buds. Later, the fungus produces great numbers of new spores which are splashed or blown from tree to tree.

Leaf curl is most active at temperatures between 50-70˚F, but can occur at relatively low temperatures. In fact, cool weather is thought to extend the infection period because new leaves are growing slowly. Wet weather is necessary for infection.

Treatment

  1. Select resistant varieties whenever possible.
  2. Leaf curl can be controlled by applying sulfur or copper-based fungicides that are labeled for use on peaches and nectarines. Spray the entire tree after 90% of the leaves have dropped in the fall and again in the early spring, just before the buds open. For best results, trees should be sprayed to the point of runoff or until they start dripping.
  3. Containing copper and pyrethrins, Bonide® Garden Dust is a safe, one-step control for many insect attacks and fungal problems. For best results, cover both the tops and undersides of leaves with a thin uniform film or dust. Depending on foliage density, 10 oz will cover 625 sq ft. Repeat applications every 7-10 days, as needed.
  4. Keep the ground beneath the trees raked up and clean, especially during winter months.
  5. Prune and destroy infected plant parts as they appear.
  6. If disease problems are severe, maintain tree health and vigor by cutting back more fruit than normal, watering regularly (avoiding wetting the leaves if possible) and apply an organic fertilizers high in nitrogen.

Peter Cundall: Act now to stop peach leaf curl disease

THERE is a reason why peach leaf curl disease is particularly prevalent in some areas.

The fungal spores need water to flow into the sticky cracks as leaf buds begin to open in August.

Heavy rainfalls during these crucial few weeks means unprotected peach and nectarine trees are certain to become infected.

If it were possible to keep the rain off the trees until all leaves have fully opened, leaf curl would be a minor problem.

We can do this with small, newly planted trees by stretching clear plastic film over several stakes to shelter branches and buds, keeping them dry.

Spraying mature trees with Bordeaux mix — a fresh blend of hydrated (builders’) lime and copper sulphate — provides a double action.

The lime lodges around unopened buds providing a temporary rainproof seal while the copper kills the fungal spores.

Burgundy mix — where lime is replaced by washing soda — is just as effective and less likely to block spray heads.

The sprays are applied at the end of July and again around the second week in August — usually when the blossom buds start to swell and turn pink.

Once leaf-tips appear a few days later, it is already too late.

The reason why codling moth grubs survive winter on or near apple trees is because they crawl deeply into cracks and fissures in the bark — or adjacent fences or shed walls — to lie dormant, secure and safe from predators. They emerge in spring to change into codling moths.

The males quickly fly off while the female moths remain, simply fluttering in the evening while giving off a scent to attract incoming males. They soon begin laying their eggs on or near small apples — or “codlings”.

Right now it pays to take a flat-head screwdriver to any apple tree, badly infested last summer, using it to peel aside all dead, flaky bark.

You’ll be astonished by the number of dormant grubs exposed, often deeply embedded in crevices.

Use the screwdriver to dispatch them and if you can get the lot (and it can be pleasantly tedious), there will be few grubby apples this coming summer.

The reason why apple and pear scab continues to attack some trees year after year is due to lack of
hygiene.

This fungal disease is now lying in wait among last season’s fallen leaves and partly decomposed fruit lying under and around the trees.

If not removed, scab spores are released in spring, drift upwards and first infect leaves (many turn a dirty black or become blotchy) and then attack the fruit.

Use a steel rake to collect all debris and cart it away, then use a mower with blades set low and catcher attached to suck up the rest.

I’ve also achieved great success by spreading builders’ lime around vulnerable trees, topping it with thick, overlapping layers of wet newsprint extending well beyond drip-lines.

You’ll need a big barrowload for each tree.

Weigh the paper layers down with a thick mulch of straw or spoilt hay.

Do this in late winter or early spring and if thick and heavy enough, this mulch will prevent most scab spores from rising in spring.

The same kind of paper-based mulch is particularly effective against pear and cherry slugs, provided it is applied in early spring.

And finally, the reason why the appalling disease brown rot keeps attacking stone-fruits before ripening is because blossoms and branches are continually reinfected each spring.

Brown rot disease is carried through winter in clusters of mummified fruit left clinging; also as cankers in infected, fruit-bearing branches (evidenced by blobs of oozing, hardening sap) and within the decayed remnants of fruit embedded in soil around the trees.

Control is by removing all mummies, a ruthless pruning to cut out all diseased wood and hard raking the ground beneath stone fruit trees to dislodge and remove all old fruit and other debris.

Then bin or burn the lot.

Autumn has arrived and stone fruit trees such as peaches, nectarines, apricots are starting to lose their leaves. This is the time to spray for Peach Leaf Curl. If left untreated, this disease affects fruit production and can get worse and worse each year.

Leaves with leaf curl appear thick and lumpy, can change colour turning pale green, pink or even purple. Flowers and fruit can also be infected by the fungus.

To break the cycle of this disease, it is important to clean up any fallen leaves and dispose of them in the bin (not in your compost). Keep the tree pruned to a nice open shape to allow good air circulation.

After all the leaves have dropped in autumn, spray the whole tree with Copper Oxychloride to kill off the spores. Spray again in late winter or early spring when you see the buds start to swell or at bud burst. Once the leaves have emerged it is too late to treat for Leaf Curl.

When the tree is growing in spring and summer, make sure you apply a quality organic fertiliser, keep it well mulched and give it regular, consistent watering. A healthy, well-fed tree is more productive and much more resistant to pests and diseases.

This is intended as general information only. Please ask one of our horticulturists for specific advice for your situation.

Peach Leaf Curl

Peach leaf curl is a virulent and resistant fungal disease that appears on the leaves of fruit trees in early spring. As the fungus Taphrina deformans lies dormant on stems, branches and then buds over winter, any effective treatment regimen must begin when an affected tree loses its leaves in late autumn or early winter.

Plants affected

Peach leaf curl predominately affects stone fruits, peaches and nectarines. It can also infect apricots and almonds.

Damage

The emerging leaves on your tree will appear thick and lumpy, taking on a blistered appearance. Foliage can change in colour to pale green, pink or sometimes purple.

Occasionally a white bloom may appear on the leaves and they will then brown off and fall.

Infected flowers will fall from the tree reducing fruit production and the fruit can also be infected, causing reddish pimples followed by fruit drop.

Left untreated, Peach Leaf Curl will continue to affect the tree year after year and become increasing worse.

Control

For the best results in controlling Peach Leaf Curl, use a number of control methods together. Complete irradication can be challenging, but the impact on the tree and fruit production can be minimised.

  • Clean up any fallen leaves from previous infections and dispose of in the bin to minimise hiding places for the fungus spore.
  • Spray with a low environmental impact copper oxychloride or lime sulphur product and winterwash (see the Winter Washing Fruit Trees page for more). Lime sulphur is preferable since it doesn’t lead to a build up of copper in the soil. This is a preventative spray, and has to be done in winter before bud burst and well BEFORE the symptoms appear.
  • If a tree is already infected, remove all distorted leaves and fruit and destroy.
  • Choose stone fruit varieties that have a lower susceptibility to the fungus.
  • Feed your soil with slow release organic fertilisers and soil conditioners, as well as regular watering regimes, to ensure it is healthy and can recover from infection.

PHOTOS: Elaine Shallue

Taphrina deformans

Fungal disease commonly found on the leaves of stone fruit such as plums, peaches, and nectarines. The fungus overwinters in crevices in the tree bark. Afterwards it affects the leaves causing them to curl up and bubble. In bad cases photosynthesis will be affected, growth of the whole tree may suffer, and the leaves may even turn brown, shrivel up, and fall off the tree.

Only a problem in severe cases, though it’s worth treating early to avoid any later complications.

Prevention

Fungal diseases like this thrive in warm, humid conditions and are more likely to badly affect unhealthy plants.

Keep plants healthy by ensuring they are well fed and watered.

Improved air flow around the tree will help to reduce the problem. Improve air flow by ensuring there is sufficient space between trees, and training and pruning the tree into an open vase shapes (for best results summer pruning is generally recommended).

Natural Treatment Options

Spray thoroughly with Liquid Copper in late winter, just as the buds begin to swell. If Leaf curl becomes a severe problem repeat spray after the tree has finished flowering.

In most cases copper sprays are allowed to used around 4 times a year under organic certification.

Preventing Leaf Curl

SERIES 26 Episode 23

Tino shows how to prevent peach leaf curl

Tino has a long-standing love affair with certain stone fruit trees – peaches, apricots and nectarines. Unfortunately for him, so does a fairly nasty fungus called Peach Leaf Curl.

The main symptom of Peach Leaf Curl is red pimple-like deformations on young leaves which, as they grow, become unsightly. The fungus reduces the tree’s ability to photosynthesise and fruit abundantly. If left untreated, the problem will get worse year after year, but the good news is, it’s a fungal disease that’s easily treated.

The fungal spores take up residence over the winter in the nooks and crannies of the tree’s bark, but mainly they reside in the leaf bud scales. When the tree breaks bud and comes back into the leaf in spring the new growth gets reinfected and the cycle starts over again.

The treatment is simplicity itself. Tino uses a fungicide containing copper hydroxide to treat the tree in late winter. He thoroughly sprays the tree, paying close attention to the fissures and cracks in the bark as well as the leaf bud scales. “For trees that are severely infected, a second application as the tree’s leaves are dropping next autumn will help too,” he says.

Other organic controls for Peach Leaf Curl include:

  • Applying copper oxychloride or lime sulphur sprays as above, or

    Bordeaux mixture .

  • Bagging and binning any affected leaves or fruit.
  • Hygiene is important – clean up any leaf, branch or fruit material that accumulates beneath the tree. Spores can overwinter in these materials, reinfecting the tree in spring.
  • Choose resistant varieties.
  • Growing strong, healthy plants that are well fertilised and watered is the best defence. A healthy plant will be better able to defend itself against pests and diseases.

A combination of these controls can treat this fungal problem with almost 100 percent success, and a happier stone fruit tree means better fruit.

Why are my peach leaves turning orange?

I think “yoda’s” above comment should be put into an answer, seeing as he has firsthand experience (IMHO).

I know for a fact, via listening to “Gardening Naturally with John Dromgoole” weekly podcast, that Texas has had an exceptionally brutal summer this year:

  • Summer heat started really early in the year.

  • Virtually zero rain fall (except for the odd very lucky area).

  • Record number of days (not continuously) over 100°F (38°C).

Those above factors have put a lot! of stress on tress, even affecting fully grown mature ones…

Is the reason why Arborist Don Gardner put together and released his “Watering Guidelines” for tress this year:

  • Do-It-Yourself Tree Care Information from City of Lakeway, TX

    • Direct link to PDF – Water Guidelines

I believe what you’re seeing (and have heard Don Gardner say the exact same thing only a couple of weeks ago), “leaves on my peach tree turn an orange-green shade” is in direct response to the weather conditions you’ve been experiencing in Texas, and is a natural survival mode that the tree has gone into ie

  • Tree starting to lose its leaves early than normal, so it can concentrate all its energy on surviving.

Just in the past week here in Missouri I’ve started to notice tree leaves (even on mature tress) browning, changing colour and falling off. Missouri has experienced a very! hot and dry July and August, more so than normal.

If the tree isn’t mulched, I would:

  • Put down a 2inch (50mm) layer of compost, starting about 4inches (100mm) away from the trunk and work outward as far as you can (is practical to-do-so).

I’d also:

  • Follow Don Gardner’s “Watering Guidelines”.

I highly recommend you listen to, “You Bet Your Garden” podcast — and start listening at 13mins:27secs in.

How to water your lawn perfectly with Guy Fipps, PhD, P.E., Director of the Irrigation Technology Center at Texas A&M University.

Ignore the above “How to water your lawn perfectly”, the watering information given by Guy Fipps, PhD, P.E. is first class (IMHO) and the link to “Irrigation Technology Center” is worth its weight in water for anyone living in Texas.

Additionally you may wish to take the time (7 minutes) to listen to this podcast:

  • Effects of Drought and Drowning on Plants

    • Direct link to MP3 – Effects of Drought and Drowning on Plants

Richard Hentschel, Horticulture Educator and Retired Extension Plant Pathologist Jim Schuster discuss drought and drowning symptoms and the long term problems with annuals, perennials and woody plants. Also discuss are methods for proper watering and indicators of drought and drowining

Peach leaf curl

Initially, the red leaf markings of the disease peach leaf curl can look quite attractive – but the affects on the plant can be devastating – especially if allowed to build up from year to year.

Description

Peach leaf curl is a crippling fungal disease of peaches, nectarines, almonds and apricots that distorts leaves and causes premature leaf fall. Loss of leaves weakens the tree and means fruit set is poor and the fruit may not fully develop.

Symptoms

Leaves that open in the spring are distorted and puckered by whitish green, pink or red blisters. Later on in the year, affected foliage will be covered with a white powdery bloom. Fruit may also carry warty spots and affected leaves will drop early.

Treatment and control

General tips

Immediately remove and destroy all infected leaves and plant parts. This will reduce the number of spores shed to overwinter on the plant and re-infect the following spring. Pick up any fallen foliage and destroy it. Do not place infected foliage on your compost heap.

An open sided polythene canopy erected above and over the tree will protect foliage from rain and dew. When placed in position from early January to the end of April this canopy will reduce infections naturally as disease spores are carried by wind and rain. This is usually only practical on wall-trained trees or small patio trees.

Spray with a suitable fungicide

Plants that show symptoms need to be protected with a suitable and approved fungicide. Currently, there is only 1 – based on copper oxychloride.

Timing of sprays is important to good control. Protect new growth with fungicide when buds begin to swell. Depending on season and location this may be from mid January to mid February. Spray again 14 days later. At the end of the growing season, pick off all affected leaves and remove all foliage debris from under the tree. After leaf fall, spray again thoroughly with fungicide to reduce the number of live spores carried on the stems and branches.

Leaf curl is a springtime disease that occurs on peach, nectarine, and related ornamental plants. The disease, though not a problem every spring, can be severe during cool, wet springs that follow mild winters. The leaf curl fungus damages peach trees by causing an early leaf drop. This weakens the trees, making them more susceptible to other diseases and to winter injury. Weakened trees also will produce fewer fruit the following season. Yield may be further reduced when blossoms and young fruit become diseased and drop.

Figure 1. Typical symptoms of peach leaf curl. Note the malformation of infected tissues.

Symptoms of leaf curl appear in the spring. Developing leaves become severely distorted (thickened and puckered), and have a reddish or purple cast. Later, as spores form on the leaf surface, the leaves become powdery gray in color. Shortly after this, the leaves turn yellow or brown and drop.

There is no secondary spread of this disease from leaves infected in the spring to new leaves produced later in the growing season. Once infected leaves drop, no further symptoms will appear during that growing season. Diseased twigs become swollen and stunted, and may have a slight golden cast. They usually produce curled leaves at their tips.

Though rarely seen, flowers and fruit may also become diseased. They drop shortly after they are infected. Diseased fruit has shiny, reddish, raised, warty spots.

Causal Organism

Peach leaf curl is caused by the fungus, Taphrina deformans. The fungus survives the winter as spores (conidia) on bark and buds. Infection occurs very early in the growing season. During cool, wet spring weather the conidia infect new leaves as they emerge from the buds. Host plant tissues are susceptible for only a short period. As the tissues mature they become resistant. The fungus produces another type of spore (ascospore) on the upper surface of the diseased leaves. During wet weather, ascospores produce additional conidia by budding. These conidia are carried to other parts of the tree by rain and wind, where they will overwinter until the next spring.

Environment can limit leaf curl infection. This partially explains why the disease does not occur every year. Leaf curl is worse when the weather is cool and wet. Low temperatures are thought to retard maturation of leaf tissue, thus prolonging the time infection may occur. The fungus can penetrate young peach leaves readily at temperatures between 50 and 70 degrees F, but only weakly below 45 degrees F. Rain is necessary for infection.

Figure 2. Peach leaf curl.

Leaf curl is not difficult to control. Since the fungus survives the winter on the surface of twigs and buds, a single fungicide spray, thoroughly covering the entire tree, will provide control. If leaf curl does result in significant defoliation in the spring, the fruit on affected trees should be thinned to compensate for the loss of leaves. Over-cropping the tree will weaken it and make it more susceptible to winter injury. For the most current spray recommendations, commercial growers are referred to Bulletin 506, Midwest Fruit Pest Management Guide, and backyard growers are referred to Bulletin 780, Controlling Diseases and Insects in Home Fruit Plantings. These publications can be obtained from your county Extension office or the CFAES Publications online bookstore at estore.osu-extension.org.

This fact sheet was originally published in 2008.

Peach (Prunus persica)-Leaf Curl

Cause Taphrina deformans, a fungus. Spores of this fungus overwinter on bark, twigs, and old infected leaves. Infection occurs through bud scales in mid- to late winter just as buds begin to swell. Slow growing shoots and leaves can be infected during cool and wet growing seasons. Maximum susceptibility is between bud break and petal fall. In wet seasons, the fungus continues to cause slight summer infection, particularly west of the Cascade Range. East of the Cascade Range, after the initial spring infection and the shedding of diseased leaves, no further evidence of the disease is visible. Photosynthetic function of infected leaves is reduced, the leaf imports sugars, and the contents of non-structural carbohydrates and enzymes involved in their metabolism are similar to sink leaves. Defoliation from severe infections weakens trees to the point that, if not controlled, they may die in 2 to 3 years.

Wetness from rain (or other factors) for over 12.5 hours is needed for leaf infection but only when the temperature is below 61°F during the wet period. Maximum infection occurs when trees are wet for 2 days or more, a frequent occurrence west of the Cascade Range. Although infected, symptoms may not appear if temperatures rise and remain above 69°F. Fruit are susceptible after petal fall until air temperature remains above 61°F. Rainfall of 0.5 inch and wetness of 24 hours is needed for fruit infection.

Symptoms The first visibly infected leaves are yellow to reddish and somewhat thickened and crisp in texture. As leaves expand they become deformed, puckered, and thicker than normal. The puckered areas are brightly colored with reds and/or purples and may continue to develop a dusty white coating of spores. Infected twigs occasionally are distorted, and a few fruit may show a reddish growth on the surface. Some infected leaves drop; others remain throughout the growing season, gradually becoming dark brown and heavily coated with spores. Ultimately, many infected leaves are shed. Trees die in 2 to 3 years from repeated defoliation.

Cultural control Resistant cultivars offer the best option for backyard growers and can be useful for commercial growers. Cultivars available today are selections from formal and informal breeding programs, chance discoveries by various growers, or propagated from trees planted by pioneers which have survived for decades. Many of these will do better if sprayed with fungicide the first year or two after planting. Trees may still die due to other problems such as shothole and/or bacterial canker. A report from North Carolina in 1981 found Redhaven and trees derived from Redhaven as tolerant but these trees are very susceptible in the PNW. The following peach or nectarine cultivars are offered by a variety of west coast nurseries as curl resistant: Autumn Rose, August Etter, Avalon, Avalon Pride, Charlotte, Early Charlotte, Early Crawford, Frost, Indian Free, Kreibich, Muir, Nanaimo, Oregon Curl Free, and Q-1-8.

Chemical control Two fungicide applications are recommended for western Oregon: at 50% leaf fall (late October), and again at delayed dormant (usually in late February, before floral buds open). A third application may be needed during the dormant season for shothole control depending on materials selected. In Washington, apply three (3) times 3 weeks apart starting in early January. East of the Cascade Range and in low rainfall areas, a delayed dormant application alone should be effective.

  • Bordeaux mixture 12-12-100. Group M1 fungicide. O
  • Bravo Weather Stik at 3 to 4.1 pints/A. Group M5 fungicide. 12-hr reentry.
  • Copper-based fungicides. Fair to good control rating. Wettable powder formulations have worked better than liquid formulations. Group M1 fungicide. O
    • Champ WG at 8 to 16 lb/A. 48-hr reentry.
    • C-O-C-S WDG at 12 to 15.6 lb/A. 48-hr reentry.
    • Copper-Count-N at 8 to 12 quarts/A. Oregon only. 48-hr reentry.
    • Cuprofix Ultra 40 Disperss at 5 to 10 lb/A. 48-hr reentry.
    • Kocide 3000 at 3.5 to 7 lb/A. Use the highest rate in western regions. 48-hr reentry.
    • Monterey Liqui-Cop at 3 to 4 Tbsp/gal water. Ineffective in western Oregon. H
    • Nordox 75 WG at 5 to 13 lb/A. 12-hr reentry.
    • Nu-Cop 50 DF at 8 to 16 lb/A with 1 pint superior-type oil/100 gal water. 48-hr reentry.
    • Previsto at 2 to 4 quarts/A. M1 fungicide. 48-hr reentry. O
  • Echo 720 at 3.1 to 4.1 pints/A. Group M5 fungicide. 12-hr reentry.
  • Ferbam Granuflo at 4.5 lb/A. Do not apply within 21 days of harvest. Group M3 fungicide. 24-hr reentry.
  • Lime Sulfur Ultra (27% lime sulfur) at 2 to 3 gal/100 gal water. 48-hr reentry. O
  • Luna Sensation at 5 to 7.6 fl oz/A. Do not use within 1 day of harvest. Unknown efficacy in the PNW. Group 7 + 11 fungicide. 12-hr reentry.
  • Ortho MAX Garden Disease Control at 3.75 teaspoons/4 gal water. H
  • Rex Lime Sulfur Solution (28%) at 6 to to 10 gal/100 gal water. The lowest rate is effective in northern California but use higher rates in western Pacific Northwest. Efficacy rating is excellent. 48-hr reentry. O
  • Syllit FL at 3 pints/A. Group U12 fungicide. 48-hr reentry.
  • Thiram Granuflo at 3.5 lb/A. Do not apply within 7 days of harvest. Also serves as an animal repellent. 24-hr reentry.
  • Ziram 76 DF at 6 to 10 lb/A. Rated excellent. Group M3 fungicide. 48-hr reentry.

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

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