- Breaking news
- How To Treat Trees With Brown Rot
- Brown Rot Fungus Treatment
- Prevention as a Control of Brown Rot Disease
- Peaches are rotting on the tree– looks like a bruise
- Brown Rot of Stone Fruits
- Brown-rot of stone fruits
- Economic importance
- Life cycle
- Control measures
- Additional Images
- Need help with what to do in your garden?
- rotten spots on all my peaches
NZ GARDENER What ripe peaches should look like! There’s no sign of the dreaded brown rot here.
Question: Have readers reported more than usual brown rot on stone fruit this year? Our five-year-old orchard of heritage fruit hasn’t had any issues with brown rot at all until this year. Will our trees be affected again next season without being treated or only if conditions are favourable again?
Answer: Brown rot is an ever-present problem in Auckland and anywhere else with humid conditions, though southern gardeners are definitely not immune either.
Brown rot is one of the most frustrating diseases for home orchardists. Just as fruit start to ripen, a furry brown mould rapidly spreads over the skin, ruining the crop. It mainly affects peaches, nectarines, apricots and cherries.
OLGA KUZYK/123RF Brown rot on a ripe peach.
Infection begins in spring, causing the blossoms to turn brown and wilt. A few infected flowers can produce enough fungal spores to ruin a whole tree. The spores are shed by the millions, spread by wind and rain, latent until the fruit is almost ripe.
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Brown rot enters the fruit via a blemish or injury, and develops quickly; fruit can rot within two days, then hang on the tree for the rest of summer shedding more spores.
Once you have spotted infection, carefully remove the mouldy, shrivelled remnants from the tree or the ground; if you leave them, millions of disease spores will reinfect the tree next spring.
You can protect stone fruit trees by pruning them in late summer during a dry spell. A spray with copper fungicide in autumn will kill brown rot spores. Repeat in spring, before and after flowering. If brown rot has been a regular problem for you, spraying through until harvest may be necessary (check the withholding period before picking fruit). Thin out the crop in early summer too. Tightly packed fruit with little air flow between each piece creates optimum conditions for disease spores to nestle in and infect neighbouring fruit.
If you’re planting new trees, choose early-ripening varieties. They will be ready to harvest before the main period of humidity in February.
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How To Treat Trees With Brown Rot
Brown rot fungus (Monolinia fructicola) is a fungal disease that can devastate stone crop fruits such as nectarines, peaches, cherries and plums. The first symptoms of the disease are often seen in spring with dying blossoms that turn to mush and form a grayish fuzzy spore mass on the branch. From there it enters the twig and cankers form. When maturing fruit is infected, the signs begin with a small brown rotted spot and rapid spore growth. The entire fruit may be consumed in a matter of days.
How to treat a fruit tree with brown rot fungus is of the utmost importance to the home gardener because the disease can and will occur again without proper precautions.
Brown Rot Fungus Treatment
For the home gardener, how to treat a fruit tree with brown rot disease is largely a case of prevention. For trees that are already infected, treatment with a brown rot fungicide is the only course of action. Diseased fruit and twigs need to be removed before the brown rot fungicide is applied. Most all purpose fruit tree fungicides are effective in the control of brown rot disease.
Prevention as a Control of Brown Rot Disease
Home brown rot control begins with sanitation. All fruit should be removed from the tree at the end of the of every harvest to prevent the rot from gaining a foothold the following year. Any damaged fruit (mummies) should be burned, as well as those twigs that are affected by brown rot cankers and even fallen unaffected fruit and twigs should be raked and burned as well.
Fungicide should also be used regularly and as directed for each particular fruit. Start fungicide treatment in the early spring before flower buds appear and reapply the fungicide every two to three weeks until the peach tree’s blossoms have faded. Resume applying fungicide when the fruit start to get their first blush of color, which should be two to three weeks before you plan on harvesting.
Since wet conditions are conducive to fungal growth, proper pruning is essential in the control of brown rot disease. Prune trees for maximum air circulation and sunlight.
Home brown rot control should also include protection against insect injury. Even small insect wounds can create openings for the fungus to find a home. Brown rot control is an ongoing process covering all aspects of fruit development and insecticides or organic insect control is a part of it.
With proper attention to the routines that should be a regular part of fruit tree health, how to treat a fruit tree with brown rot will not be as devastating as it initially appears.
Peaches are rotting on the tree– looks like a bruise
I would probably need to see a photo or the tree itself to be certain, but it sounds like “brown rot,” which is a very common disease among peaches in our area. For now, I would suggest using a “fruit tree spray” (containing a multi-purpose fungicide) or another general purpose fungicide, such as Daconil, now and again in 10-14 days. Then once more about 3 weeks before they’re ready to harvest to protect them through the rest of the season. The fungicides that are available are primarily preventative and not curative. So, it won’t cure the infected fruit, but it may help protect what is left.
Next year I would recommend using the fungicide only, during the bloom (don’t use the “fruit tree spray” which contains an insecticide that you don’t want to use during the bloom as it can kill bees and other pollinators). After the blooms are gone, go back to using the “fruit tree spray” as recommended by the label.
I hope this is helpful and that you have success with the remainder of your crop.
Brown Rot of Stone Fruits
Brown rot is a common and destructive disease of peach and other stone fruits (plum, nectarine, apricot, and cherry). The brown rot fungus may attack blossoms, fruit, spurs (flower and fruit bearing twigs), and small branches. The disease is most important on fruits just before ripening, during and after harvest. Under favorable conditions for disease development, the entire crop can be completely rotted on the tree. Peaches not kept in cool storage may be rotted in two to three days by the fungus.
Figure 1. Brown rot on peach fruit. Note that the fungus has invaded the twig causing a twig blight as well.
Figure 2. Brown rot producing spores on the surface of an infected peach fruit. These spores can infect other fruit.
The symptoms of brown rot are very similar on all stone fruit. Symptoms first appear in the spring as the blossoms open. Diseased flowers wilt, turn brown, and may become covered with masses of brownish-gray spores. The diseased flowers usually remain attached into the summer.
Young fruits are normally resistant, but may become infected through wounds. As fruits mature they become more susceptible to attack, even in the absence of wounds. Fruit infections appear as soft brown spots which rapidly expand and produce a tan powdery mass of conidia. The entire fruit rots rapidly, then dries and shrinks into a wrinkled “mummy.” Rotted fruit and mummies may remain on the tree or fall to the ground. Fruit infection may spread rapidly, especially if environmental conditions are favorable and fruits are touching one another.
The fungus may move from diseased blossoms or fruit into the spurs. The fungus may then invade and cause diseased areas (cankers) on the twigs below. Succulent shoots are sometimes infected by direct penetration near their tip. A canker may form encircling the twig, causing death of the twig beyond the canker (twig blight).
Brown rot is caused by the fungus Monilinia fructicola. The brown rot fungus survives the winter in mummified fruits (either on the ground or still on the tree) and in twig and branch cankers produced the preceding year. Both sources may produce spores that can infect blossoms and young shoots. At about blossom time, a mummified fruit that has fallen on the ground produces up to 20 or more small, tan, cup-like structures on slender stalks that are called apothecia. As an apothecium matures, it becomes thicker and the cup opens to a bowl-like disc 1/8 to ½ inch in diameter across the top. The inner surface of each bowl is lined with thousands of spore-containing sacs (asci). At this stage, the slightest disturbance of air movement will cause an apothecium to forcibly discharge millions of spores.
Figure 3. Brown rot on cherry fruit. Note the tufts of fungus on the surface of rotted fruit.
These spores (ascospores) are carried by wind to the open or unopened blossoms and young shoots. If a film of water (either from dew or rain) is present for 5 hours or longer, the spores can germinate and penetrate the plant. Infected blossoms soon wilt and tan-gray tufts, composed of masses of another type of spore (conidia), develop on the outside of the flower shuck. If the infected blossom does not drop off, the fungus soon grows through the pedicel to the twig and forms a canker.
Masses of conidia are soon produced on the newly cankered twig surface during moist periods throughout May and June. These summer spores are easily detached, and, like the ascospores, are mainly wind-borne. They are also splashed by rain or carried by insects to the growing fruit. Brown rot conidia can germinate and infect at temperatures of 32 to 90 degrees F. Wet weather and temperatures ranging from 60 to 70 degrees F are most favorable for disease development.
Following spring and summer rainy periods, mummified fruit still hanging in the tree become covered with masses of conidia that may result in blossom blight or fruit rot. Mummies hanging in the tree do not produce ascospores. Although the flesh of young fruit is very susceptible to brown rot infection, the fruit has such a tough skin that the germ tubes of the summer spores do not normally penetrate. For this reason, young uninjured fruits are fairly safe from infection.
However, any type of injury to the fruit will provide entry points for brown rot spores. Insect and hail wounds, fruit cracking, limb rubs, twig punctures, and a variety of picking and packing injuries greatly increase the losses due to brown rot. Growers must realize that brown rot spores are practically everywhere during the fruit-ripening period. Infection is almost certain to occur if the weather is moist and if the fruit skin is broken in some way.
- Sanitation is very important in controlling brown rot. All dropped and rotted fruit should be picked up and destroyed promptly. At the same time, remove all mummies from the trees. Prune out all cankers during the dormant season. Overripe or rotting fruit in the packing shed should be removed and destroyed at once.
- Control of insects that feed on fruit is essential. Remember that anything that causes wounding of the fruit will increase the incidence of brown rot. Special care should be taken during harvesting and packing to prevent puncturing or bruising of ripe fruit.
- Remove wild or neglected stone fruit trees that serve as reservoirs for the disease.
- Fruit should be cooled and refrigerated (as close to 32 degrees F as possible) immediately after harvest.
- The use of fungicide is an important part of the disease management program for brown rot.
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.
|Figure 4. Brown rot mummy from an infected peach.||Figure 5. Brown rot disease cycle. We want to thank the New York State Agricultural Experiment Station for use of this figure. Taken from Tree Fruit IPM Disease Identification Sheet No. 2.|
This fact sheet was originally published in 2008.
Brown-rot of stone fruits
Note Number: AG0158
Published: December 1999
Updated: August 2010
The fungal organisms that cause brown-rot of stone fruits in Victoria are Monilinia fructicola and Monilinia laxa. A third species of Monilinia, M. fructigena, affects pome and stone fruit in Europe and Asia, but has not been recorded in Australia.
The symptoms of brown-rot are blossom blight, twig blight, cankers, leaf shot-hole, quiescent infection and brown-rot of the fruit.
- Blossom blight. This is a faint discolouration of the affected flower part. The fungus grows rapidly and the entire floral structure is soon brown and shrivelled and masses of spores are produced. A canker may develop at the base of the flower.
- Twig blight. If weather conditions are favourable for the fungus beyond the blossoming period, twig blight may follow flower infection. Small cankers at the base of dead flowers may extend until they girdle the twig, which will wilt and die (Figure 1).
- Cankers may continue to extend towards a larger branch and may affect two-year-old and three-year old wood. Gumming from cankers occurs.
- Leaf shot-hole. Young leaves become infected and a shot-hole symptom develops.
- Quiescent infection. On green fruit, M. fructicola sometimes forms visible lesions which remain dormant until the fruit approaches maturity. Quiescent infections may be invisible or appear as small necrotic or brown- red lesions or haloes on the fruit surface. These lesions may become active and cause rotting of the fruit before or after harvest.
- Brown-rot of fruit. Infection of the fruit usually occurs as the fruit approaches full ripeness. A rapidly spreading firm brown rot develops and the fungus produces masses of fawn-coloured spores often in concentric zones. Infected fruit shrivel to a “mummy”. If this remains in the tree it continues to produce spores (Figure 2 and 3). Brown rotted fruit in cold storage appear black and there may be no signs of sporulation.
Figure 1. Blossom blight and twig death near an elliptical brown rot canker on an older branchFigure 2. Brown rot infection of immature cherriesFigure 3. Brown rot infected canning peach (right)Figure 4. Brown rot infection in a tray of nectarines
Brown rot can cause serious losses to stone fruit especially in seasons with very wet weather during flowering or immediately pre-harvest. Losses are mainly associated with blossom blight (which reduces fruit set and potential yield), and brown rot on maturing fruit close to harvest. Significant losses can also occur to fruit after harvest (Figure 4). The disease is widespread throughout Victoria. In the past major losses occurred throughout the extensive stone fruit production areas in eastern Australia; however such losses have been generally rare in recent years. This is largely due to improved management practices and more effective fungicides.
The disease is carried over from season to season on mummified fruits, peduncles, cankers and infected wood left on the tree. Fruit and wood which fall and remain on the ground are also significant sources of infection. Blossom blight occurs to a greater or lesser extent in most years, and infected blossoms continue to produce spores up to and throughout the harvest period. Injuries caused by insect pests, hail or fruit splitting allow the establishment of infections and subsequent formation of spores. Fruits which fall to the ground in the pre-harvest period and during harvest are readily infected with brown rot and are considered to be of major importance in the starting of severe outbreaks.
- Orchard sanitation plays an important part in the control of brown-rot. During the winter all fruit mummies and wood showing cankers should be removed from the tree and from the ground and be burnt.
- For the control of blossom blight, apply a suitable fungicide at bud-swell. Further sprays registered for the control of brown-rot should be applied at early (20% to 30%) bloom and early petal-fall stages. During prolonged blossoming, particularly in showery weather, several sprays will be needed to give adequate protection against infection.
- To prevent infection of the ripening fruit, spray with a suitable fungicide a month before harvest. This spray should be repeated a fortnight later. Extra sprays may be needed if there are frequent rains within the month before harvest.
- To prevent development of fungicide resistant strains of the disease, do not use a complete spray program of any one particular fungicide. Refer to Fungicide Resistance Action Committee (FRAC) guidelines for further information.
- Control of insect pests (especially Carpophilus beetles) that injure the fruit and which may also vector the disease is essential for the control of brown-rot.
- Post-harvest treatments for brown-rot control must be applied as soon as possible after harvest.
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.
This Agriculture Note was published in December 1999.
It was most recently reviewed by W.S. Washington, Plant Standards in August 2010.
Published and Authorised by:
Department of Environment and Primary Industries
1 Spring Street
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
Presence of powdery gray masses on the surface of rotting fruit is characteristic of brown rot. (Photo credit:Wayne Griffiths)
Ashley Ellinghuysen, UW-Madison Plant Pathology
Item number: XHT1220
What is brown rot? Brown rot is a destructive fungal disease of trees and shrubs in the genus Prunus which includes peaches, plum, cherries, apricots and nectarines. Brown rot is particularly a problem on the fruits of susceptible plants, with the potential to cause losses of 50% or more prior to harvest. After harvest, additional losses due to the disease are possible if fruits are injured, bruised or stored at warm temperatures with moisture.
What does brown rot look like? Initial symptoms of brown rot often occur in the spring as brown spots on blossoms. Affected blossoms eventually collapse completely, and can produce a gummy material that sticks to twigs leading to infections and subsequent twig dieback. Fruits that develop from healthy flowers can become infected as they mature leading to a brown fruit rot that quickly encompasses an entire fruit. Eventually, affected fruits will dry and shrivel to form “mummies”. Characteristic powdery, gray masses of spores form on the surfaces of both rotting fruits and mummies.
Where does brown rot come from? Brown rot is caused by two fungi in the genus Monilinia (primarily M. fructicola and less commonly M. laxa). These fungi may be introduced into a garden via airborne spores produced on nearby wild or volunteer Prunus trees and shrubs. Insects such as sap beetles, vinegar flies and honeybees can also transport spores. These insects are attracted to brown rotted fruit and can subsequently visit and drop off spores on otherwise healthy fruit. Wounds due to insect feeding or hail can provide an entry point into fruits for brown rot fungi. Further spread can occur when infected and healthy fruits touch. Once introduced into a garden, brown rot fungi can overwinter on infected twigs and in mummified fruits that are hanging from trees or have fallen to the ground. Initial infections each spring are typically due to spores that are blown or splashed from twigs or from the gray masses on mummified fruits. More rarely, mummified fruits that are partially or shallowly buried in the ground will produce small (up to 1/16 inch diameter) mushroom-like structures called apothecia. Apothecia produce a second type of spore that can cause infections. Brown rot can occur under a wide range of temperatures (40 to 86°F), but tends to be more of a problem when the weather is warm (i.e., 68 to 77°F) and wet (i.e., with three or more hours of rain or dew formation).
How do I save a tree with brown rot? Luckily, brown rot is not a lethal disease. However, once fruits are infected, there are no curative treatments. To manage twig infections, prune four to six inches below sunken or dead tissue on each branch. Dispose of these branches by burning (where allowed by local ordinance) or burying them. To prevent spread of brown rot fungi on pruning tools, decontaminate tools between each cut by dipping them for at least 30 seconds in a 10% bleach solution or preferably (due to its less corrosive properties) 70% alcohol. Rubbing alcohol and many spray disinfectants contain approximately 70% alcohol and are easy to use.
How do I avoid problems with brown rot in the future? Remove and destroy any wild or volunteer Prunus trees and shrubs on your property, as well as all rotting and mummified Prunus fruits, as these can be reservoirs for brown rot fungi. Burn (where allowed by local ordinance) or deep bury these materials. Thin your Prunus trees to increase air flow and promote more rapid drying of twigs and fruits. See University of Wisconsin Bulletin A3629, “Growing Apricots, Cherries, Peaches, and Plums in Wisconsin” (available at http://learningstore.uwex.edu) for information on how and when to prune. Be sure to decontaminate cutting tools after tree/shrub removal and pruning as described above. Carefully handle fruits during harvest to minimize bruising and store fruits in a cool, not overly wet environment.
If brown rot has been a chronic problem in your garden and the cultural methods discussed above have not proven successful for control, consider using fungicides. Select products that are labeled for use on apricots, cherries, peaches and/or plums and that contain captan, myclobutanil or propiconazole. To prevent blossom infections, make one application when approximately 10% of flowers are open. To prevent fruit infections, begin making applications three weeks before anticipated harvest, particularly if there is wet weather. When applying more than one application, DO NOT use myclobutanil and/or propiconazole for all treatments as these active ingredients have similar modes of action; excessive use of these active ingredients can select for fungicide-resistant strains of brown rot fungi. Instead, alternate use of these active ingredients with use of captan or only use captan (which is not known to have problems with resistance development) for control. Also consider insecticide treatments to manage insects that can damage fruits and provide entry points for brown rot fungi. See University of Wisconsin Extension Bulletin A2130, “Apricot, Cherry, Peach, and Plum Pest Management for Home Gardeners” (available at http://learningstore.uwex.edu) for suggested insecticides and timings of applications. Be sure to read and follow all label instructions of any fungicides and insecticides that you select to ensure that you use these products in the safest and most effective manner possible. Be especially careful not to apply any pesticides closer to harvest than is allowed on the label.
Need help with what to do in your garden?
Q What is brown rot?
A It’s a fungal disease which can affect many types of fruit. It gets its name from the resulting brown patches that may engulf the fruit. The disease starts by attacking fruit that has already been damaged by pests – especially wasps and birds – or has been bruised.
Once the infection builds up it can affect otherwise undamaged fruit. Brown rot can spread very quickly, especially among stored apples or pears. Earlier in the season, this fungus is also one of the causes of blossom wilt and shoot wilt on fruit trees and their ornamental relations, such as flowering cherries and almonds.
Caption: Brown rot attacks ripe fruit that has been damaged by pests or bruised
Q How do I recognise brown rot?
A It appears as soft brown patches on ripe fruit. Apples, pears and plums are especially susceptible. Grey or white fluffy dots, or pustules, may also develop on the surface, often in concentric rings. It spreads quickly, both on the branch and in stored fruit brown cankers on the twigs. These, too, will develop grey or yellowish white pustules in wet weather.
Q Could I mistake brown rot for anything else?
A There are many other fruit rots, especially among stored fruit. Eye rot gives rise to round, sunken, rotten patches near the flower end of the fruit, whereas bitter or gleosporium rots have brown, saucer-shaped blotches with rings of fungal pustules inside. Neither of these diseases produces the characteristic flower attacks or twig cankers of brown rot.
In storage, several moulds, such as grey mould (botrytis) and penicillium moulds, produce soft, fluffy rots.
Q What causes brown rot?
A The fungi Sclerotinia fructigena and S. laxa are responsible. They are sometimes referred to as Monilinia fructigena and M. laxa.
Sclerotinia fructigena hits apples, pears, medlars, quinces and stone fruits, while S. laxa affects stone fruits like plum, peach, almond, apricot and cherry – although fruit with pips are not entirely free from risk.
Similar fungi attack the fruit of other trees such as hawthorn, quince and medlar. Deal with these in the same way as brown rot.
Q Can you tell me any more about brown rot?
A Brown rot overwinters in cankers on shoots, in mummified fruits still on the branches or in fallen fruit. The mummified fruits seem to persist as a source of the disease for several years.
In spring, spores are released; these go on to cause blossom infections and travel to new sites on the breeze, by rain splash or carried by insects. They multiply quickly in floral parts when the weather is wet, releasing more spores. These go on to create more floral infections.
At the same time, the fungus spreads from the afflicted flower on to the shoots and spurs, where cankers develop.
Look out for tufts of fungal growth on these cankers, about 3mm across and yellow (S. fructigena) or grey (S. laxa).
When the fruit is fairly large, the disease spreads from the cankers to the fruit. This usually only happens when there has been bird, insect, hail or wind damage to the fruit.
Once inside the fruit, brown rot will spread at points where the bunches of fruit are close enough to touch. The effect of the fungus is to shrink and wrinkle the fruit, forming ‘mummies’. The fungus also spreads by contact in store, so boxes of apples are spoiled.
Q How do I control brown rot?
A Remove all infected fruit as soon as you spot them while the crop is ripening. This will help reduce the spread of the fungus. Give plum trees priority, as brown rot can ruin the entire crop. In winter, cut out and burn cankered twigs to reduce the number of disease spores.
Even when there has not been much brown rot it is still worth being vigilant, as the disease can quickly become troublesome if the weather favours it the following year. Also try to destroy wasp nests and net small fruit trees to keep out birds. This limits the initial damage that lets the brown rot into the fruit.
Caption: Pick off infected fruits to reduce the amount of fungal spores released
Q Should I collect rotten fruit?
A Picking up fallen fruit and removing shrivelled, mummified plums from the tree should reduce the amount of fungal spores released into the garden.
However, large quantities of half-rotten fruit are difficult to dispose of completely. It is questionable how much control this technique offers as any rotten fruit left on the ground will produce large amounts of light, easily dispersed spores, spreading the disease widely.
Q What about stored fruit?
A Reduce rotting in store by keeping only undamaged fruit. Check stored fruits weekly. Try to keep the fruit as cool as you can.
Q Can brown rot be sprayed?
A There are no recommended fungicides for gardeners to use on brown rot in Britain
Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa
Client: I have 5 different varieties of nectarine and peach trees in my Central CCC backyard. I treat the trees in late winter for peach leaf curl using an organic – approved spray. That works great.
Nectarine with Brown Rot
picture: UCANR My problem is that last year the fruit on one of my nectarine trees started rotting on the tree. The tree is about 6 years old. The fruit rots to a dark brown color. None of the other nectarine or peach trees have the same problem.
What do you think the problem is? What is the cure? I prefer to use organic methods.
Advice from the MGCC’s Help Desk: Thanks for contacting the MGCC Program’s Help Desk. From your description, the problem with your nectarine fruit appears to be caused by the “brown rot fungus”, monilinia fruiticola. Peaches can be attacked by Brown Rot as well.
Brown rot fungus is tough and can survive over the winter:
- in infected twigs
- inside dead blighted blossoms that remain on the tree
- dry mummified fruit that has been left on the tree from the previous year
- dry mummified fruit left on the ground from the previous year
Brown rot infection and disease development can take place over a wide temperature range and flowers can be infected from the time buds open until petals fall. Water must be present on the flower surface for infection to occur. Spores produced on the tree parts described above in spring are carried through the air by wind and splashing water to infect flowers of the new year’s crop.
Peach with Brown Rot
picture: goodfruit.com Prompt removal and destruction of fruit mummies and diseased plant parts prevents the buildup of brown rot inoculum and helps keep rot below damaging levels. Pruning trees to allow good air movement will also help. Good air circulation through the tree facilitates rapid drying of the foliage and flowers after rain or overhead irrigation (not recommended). Some varieties of nectarine are more susceptible to brown rot than others, as you have seen in your own garden!
Appropriate applications of fungicide is the usual preventive measure to prevent brown rot, especially if you’ve had it occur before. However, fungicides can only prevent brown rot; they will not cure brown rot so timely application is important. Organic fungicides do not appear to be readily available for home gardeners. Recommended applications of copper-containing fungicides or synthetic fungicides such as myclobutanil at pink bud stage – just before the buds open can help avoid serious fruit losses. Rainy periods will require more spray. Additional applications when fruit starts to color may be needed if rainy weather persists. Do not apply copper compounds after bloom.
More specific information can be found by following the links below:
Good luck this year with your nectarines. Hopefully, pruning, sanitation, cultural care, and a timely application of a fungicide will minimize brown rot.
Please let us know if you have any further questions we can help you with, and thank you for contacting our program!
Help Desk of the UC Master Gardener Program of Contra Costa (JMA)
rotten spots on all my peaches
This sounds like brown rot. It is very common here. It can be worse in wet springs.
We don’t recommend using combination fruit tree sprays, because they apply pesticides at times when you don’t need them, and contain chemical pesticides that are more toxic while there are others that are less so but will do the job.
The timing of spray schedules for fruit trees is pretty strict and starts as early as dormant, pre-bloom stage, and can repeat right up to almost harvest depending on what you are treating for.
Peaches have many problems in our area. Take a look at this page, which has spray schedule information: http://extension.umd.edu/growit/stone-fruit-peaches-cherries-plums-apricots-nectarines
To control Brown Rot, spraying of a fungicide (with not other ingredients) is done very early in the season, when blooms are 5% open and again at 95% open, then cover sprays approximately every 14 days until 2 weeks before harvest.
Read through the links. There are cultural ways of managing your orchard to help with diseases and pest too.
It is not easy to grow good tree fruits in Maryland.
Small fruits like berries or figs are much easier.