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.
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.
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.
This article was last updated on
Read more about Peach Trees
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.
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.
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.
Chemical control practices:
Post-harvest control measures:
Download a printer-friendly version of this publication: Brown Rot of Stone Fruits (pdf)
Do you have a question -or- need to contact an expert?
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.