Peach Brown Rot Control: Treating Brown Rot Of Peaches


By: Mary Ellen Ellis

Growingpeaches in a home orchard can be a great reward come harvest time, unlessyour trees are hit by brown rot. Peaches with brown rot can be completelydestroyed and become inedible. This fungal infection can be managed withprevention measures and with fungicides.

What is Peach Brown Rot?

Brownrot is a fungal infection that can impact peaches and other stone fruits.Brown rot of peaches is caused by the fungus Monilinia fructicola. It infects trees in two stages. Duringblossoming, flowers will develop brown spots and quickly die. Look for dustyfungal growth on the dead blooms and cankers on the twigs.

The infection can also set in during peach ripening,triggered by the fungal growth on the flowers and twigs in the spring. Peacheswith brown rot have brown spots that quickly spread. The infection moves fast,rotting entire fruits in just a couple days. Eventually, an affected peach willshrivel up and drop to the ground. This is an important source for ongoinginfection.

Peach Brown Rot Control Methods

Brown rot on peach trees can be treated with fungicides,including myclobutanil or Captan, but there are also things you can do toprevent the infection or manage and control it without losing too much fruit.

The infection begins in temperatures as low as 41 degreesFahrenheit (5 Celsius), but 77 F. (25 Celsius) is the ideal temperature. Wateron petals and twigs is necessary for infections to begin in the spring.Avoiding overhead watering and keepingtrees thinned adequately for good airflow and drying after rains isimportant.

Good sanitary practices in the orchard is among the bestthings you can do to control brown rot of peaches. Any fruit you thin from thetree should be removed and destroyed. Clean up under trees in fall, after harvestingpeaches, and remove any rotted fruits especially. If you see signs ofinfection in the spring blossoms that spread to twigs, trim out those twigs showingcankers during the summer months.

Wild plum can be an important source of infection by brownrot, so if you have had issues with this disease, check areas around yourorchard. If you have wild plums, removing them can help prevent the disease andreduce infection rates in your trees.

When you harvest peaches from a tree that was impacted bybrown rot, it may help to give each fruit a quick dip in a water bath. Studieshave found that immersion for 30 to 60 seconds in water at 140 degreesFahrenheit (60 Celsius) significantly reduces decay in the fruit. Then storethe fruit in cold temperatures.

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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
Revised: 6/22/2013
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.


New Fungicide for Peach Disease Control

The fungicide Luna Sensation has been registered for use on peach. This fungicide was previously registered on apple and cherry in 2012. Due to its recent release this spring for peach disease control, Luna Sensation was not included in the latest 2016 publication of the New Jersey Commercial Tree Fruit Production Guide. Thus, below is a discussion of its attributes and suggested usage for disease control on peach.

Luna Sensation, manufactured by Bayer, is currently labeled for use on stone fruit, pome fruit, blueberries, and other berries. Within the stone fruit group, Luna Sensation can be used on a wide variety of crops, including peach, nectarine, Japanese and American plum, apricots, sweet and tart cherry, and plumcots. The labeled stone fruit rate range is 5.0 to 7.6 fl oz/A with a preharvest interval (PHI) of 1 day and a restricted-entry interval (REI) of 12 hours.

The active ingredients in Luna Sensation are fluopyram and trifloxystrobin, which are classified as SDHI (FRAC group 7) and QoI (FRAC group 11) fungicides, respectively. When combined, these active ingredients bestow preventative, systemic, and curative properties to the fungicide. The Luna or fluopyram active ingredient inhibits spore germination, mycelium growth, and sporulation of fungal plant pathogens. QoI fungicides in general, including trifloxystrobin, also exhibit similar activity.

Luna Sensation has been tested on peach over a six year period at the Rutgers Agricultural Research & Extension Center. Based on these field trials, Luna Sensation has been rated as excellent for control of brown rot blossom blight and fruit rot and good for control of rust spot and scab. The 5.0 fl oz/A rate was used in most of these studies it is possible that higher rates may provide better control of rusty spot and scab. Pristine and Merivon fungicides, both manufactured by BASF, have the same two types of active ingredients (SDHI+QoI). Like Luna Sensation, they also provide excellent control of the blossom blight and fruit rot phases of brown rot. However, these two materials have provided only fair control of peach scab and rusty spot.

The SDHI fungicides have been rated by FRAC to have a medium to high risk of resistance development, while the QoI fungicides were rated has having a high risk. Thus, a number of important usage restrictions were built into the Luna Sensation label. For stone fruit, a maximum of four applications are allowed per year with a maximum dosage of 27.3 fl oz per acre per year. Furthermore, no more than two sequential applications of Luna Sensation (or any group 7 or 11 fungicides) are allowed before switching to a fungicide from a different group. Finally, no more than 0.446 lbs of fluopyram and 0.5 lbs of trifloxystrobin per acre per year can be applied. This latter restriction is particularly noteworthy since the fungicide Gem, which has trifloxystrobin as its active ingredient, is often used in peach programs.

The recommended use for Luna Sensation is for peach brown rot control during the preharvest fruit ripening period. Since Luna Sensation contains SDHI and QoI fungicides, the DMI fungicides, such as Indar, Orbit, PropiMax, Orius, or Quash are ideal candidates for rotation during this period. In 2015, two such integrated programs were evaluated for control of brown rot using a three-spray program with applications at 18-, 9-, and 1-day preharvest (dph). The first program consisted of Luna Sensation at 18- and 1-dph with Indar at 9-dph the second program consisted of Indar at 18- and 1-dph with Luna Sensation at 9-dph and a third standard program consisted of Gem-Indar-Fontelis for the three sprays. These programs yielded 91%, 97%, and 91% control of fruit rot, respectively, and were not statistically different from each other.

Although Luna Sensation and many other SDHI, QoI, and DMI fungicides can provide excellent control of blossom blight, these materials are best “saved” for use in controlling the fruit rot phase of brown rot. Other fungicides of different chemistry, such as Rovral and Meteor (dicarboximides) Topsin-M (MBC) and Vangard and Scala (AP) can provide excellent control of blossom blight and are therefore recommended for use early in the season. Three of these materials, namely Rovral, Meteor, and Vangard, cannot be applied past bloom, so employing these different chemistries “up front’ makes sense as a resistance management strategy.

A second fungicide from Bayer, Luna Experience, was also recently registered for use on stone fruit crops. This fungicide also has fluopyram (SDHI, FRAC group 7) as one of its active ingredients combined with tebuconazole (DMI, FRAC group 3) as its second active ingredient. Efficacy ratings and recommendations for usage are not available at this time additional field data are needed.


Control

Many fungicides are labeled for brown rot, including azoxystrobin, benomyl, chlorothalonil, opper sulfate, fenbuconazole, iprodione, myclobutanil, propiconazole, sulfur, thiophanate-methyl, triforine, and vinclozolin. It takes a combination of cultural and chemical control practices to effectively manage this disease.

  • Remove infected and injured fruit during and following each growing season.
  • Prune any cankered or dead stem and branch tissue to reduce the inoculum load (the amount of pathogen in the infected tree) and prevent outbreaks.
  • Improve air circulation by pruning branches and thinning fruit so that ripening fruit do not touch one another. This helps reduce wet conditions on the fruit, decreasing the probability and/or severity of infection.
  • Do not leave thinned fruit on the ground since they may be colonized by the pathogen and contribute to the inoculum load (Fig. 3).
  • Choose more resistant peach varieties such as Elberta, Glohaven, and Babygold No. 5.

Chemical control practices:

  • Alternate between chemicals in different Fungicide Resistance Action Committee (FRAC) groups with different modes of action (the way a particular fungicide interacts with the pathogen to kill it). This helps avoid resistance to fungicides because of repeated applications of the same one. (See www.frac.info/ for the annual FRAC code list.)
  • Apply fungicide during bloom and just before harvest. A preventive treatment just before bloom,when pink begins to show out of the buds, may also be needed, particularly if weather conditions favor the development of the disease.
  • Evaluate the need for additional applications throughout the season based on weather conditions, disease symptoms, and the fungicide(s) being used.

Post-harvest control measures:

  • Carefully handle fruit during and after harvest to prevent bruising or other injury.
  • Store fruit in a cold environment.
  • Treat with fungicides and biological control agents, including certain strains of Pseudomonas and Bacillus spp., to protect against post-harvest rot.

Download a printer-friendly version of this publication: Brown Rot of Stone Fruits (pdf)

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Other Fungicides

  • Captan is effective in apple orchards against scab, black rot, white rot, bitter rob, Brooks spot, and blossom end rot. It is effective against sooty blotch and fly speck if the last spray application is not more than 30 to 40 days before harvest. It is not effective against the rusts, fire blight, or powdery mildew.
    Where the early-season apple scab control program fails and scab becomes established in the trees, Captan at low rates cannot be expected to provide control. This fungicide is highly effective, however, in reducing spore germination.
    On stone fruits, Captan is a good fungicide for the control of brown rot and scab, when adequate spray schedules are followed. Captan plus wettable sulfur can be used on peaches when brown rot, scab, and mildew are present. Captan is effective against cherry leaf spot and brown rot on tart cherries if the diseases are at a low level and the spray intervals do not exceed 2 weeks.
    On apples, Captan can cause a necrotic spotting, yellowing and dropping of leaves when used under poor drying conditions or in combination with sulfur, especially on Delicious and Stayman varieties. Dead spots on fruit and foliage have occurred on both plums and prunes when Captan is used from petal fall until the fruit begins to ripen. Captan is not registered for use on pears. The leaves of some sweet cherry varieties may be injured by repeated Captan applications.
    Captan has few spray incompatibilities, but it should not be used with oil, lime, or other alkaline materials. The use of Captan within 1 to 2 weeks either before or after an oil application may result in leaf injury on apple trees. Combinations with sulfur might result in increased injury under high temperatures and high relative humidity.

Chlorothalonil (Daconil 2787) is a broad spectrum, non-systemic fungicide. It is labeled for a small number of fruits including peaches, cherry, and plum. Helps control several early-season diseases. Read the product label for further information.

General Purpose Mix, GPM (home orchard spray) contains both a fungicide and an insecticide to control a range of insects and diseases. Captan is usually the fungicide. Methoxychlor, malathion, or Carbaryl (Sevin) are the insecticides. There are newer GPMs on the market with the active ingredients lamda-cyhalothrin (pyrethroid-insecticide), pyraclostrobin (fungicide) and boscalid (fungicide). GPMs generally are not recommended, especially early in the season. During the bloom period a fungicide may be needed but GPMs always contain insecticides. Carbaryl (Sevin) is a broad-spectrum insecticide that is especially harmful to honeybees and kills spider mite predators, thus encouraging large spider mite populations.

  • Immunox (myclobutanil) is a fungicide with some systemic action. It is labeled for use on apples to control powdery mildew, rust and scab, on stone fruits to control powdery mildew, and brown rot, and on grapes to control powdery mildew and black rot. Be careful not to purchase Immunox Plus, which is mixed with an insecticide and is not labeled for edible plants.

  • Watch the video: How to Grow Peaches Organically - Complete Growing Guide


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