If you have ever tried growing stone fruits like peaches or plums, then you might have struggled to ever get fruit. This is particularly if you live in the hot humid environment of the southeast. In the spring your trees flower, you get a promising set of happy looking fruit, then shortly before they start to ripen the fruit rots on the tree. If you have been paying attention and watching closely, you might have noticed small dark spots appear on the fruit prior to them rotting. Congratulations, you are looking at the symptoms of brown rot.
Brown rot is caused by a fungus, Monilinia fructicola. This one fungus single-handedly makes growing stone fruit an impossibility, or impracticality for many backyard growers. Unfortunately, brown rot is difficult to control even for commercial growers. Many strains of it are now resistant to common fungicides available to non-commercial growers making succeeding at peaches doubly difficult for hobbyists.
Understanding brown rot
To understand how to control brown rot we need to understand its basic life cycle. As we mentioned above brown rot is a fungus. It overwinters on stem cankers or on fruit mummies. In the spring when the trees flower the blossoms get infected with fungal spores and the young fruit gets infected. Sometimes you see symptoms of brown rot on the blossoms, but typically stone fruit trees flower so prolifically that you don’t really notice the blighted blossoms. Even with some brown rot infection in the blossoms the trees typically set an ample fruit crop.
The fungus then sits latent until your fruit starts to ripen. Green fruit is not particularly susceptible to brown rot. However, the young fruits can be infected from infected blossoms or mechanical damage from insects. While the fruit is green, you likely think that your crop is just fine as it shows no symptoms of rot. Then when the fruit gets close to ripening it suddenly all rots. At this point it is too late to save the fruit.
There is no curative treatment for brown rot, so it is essential to do your best to prevent infection.
Unfortunately, for homeowners wishing to produce organic or no spray fruit, there is also no organic solution to brown rot. Brown rot is what typically stands in the way of a backyard spray program being organic. Thus, you should carefully consider whether you are willing to commit to spraying fungicides many times a year before planting stone fruit trees. Even with an expensive fungicide program, it is entirely possible to have a complete loss of your fruit crop.
Sadly, stone fruits can be particularly disappointing and unrewarding to grow for many people.
If knowing this you still wish to attempt to grow peaches, plums or cherries, you should start your brown rot control program in the winter months. Go through your orchard and remove all the mummies both from the trees and the ground. Mummies are the shriveled fruits infected with brown rot. Then as you are pruning your tree remove all the brown rot cankers you can find.
Be sure to burn, bury, or otherwise dispose of the brown rot material. Don’t throw it on your compost heap! You should also remove any wild Prunus species trees around your property if at all possible. Plants like wild cherry trees will harbor and spread the fungus. Your goal should be to minimize the amount of inoculum available to infect your fruits come spring.
Then you will need to commit to a stringent fungicide spraying program.
They usually involve spraying just before your buds open, once they start to fade and you have small fruits. Then spray fungicide weekly starting a few weeks prior to when you expect the fruit to ripen. We recommend checking with your local university extension for an up to date brown rot spray program tailored to your specific location. It can also be particularly helpful if you do not know when to expect fruit to ripen in your area. Environments vary widely, and the appropriate spray program in Georgia might not be correct for New Hampshire. Plus, brown rot has proven itself adaptable enough to develop resistance to common fungicides in many areas.
If you do start to see infected fruit on your tree. Remove and destroy them immediately. Brown rot can spread rapidly on ripening fruit. This is particularly true if conditions are favorable (warm and wet), or the fruits are touching. It is also important to control insects such as plum curculio that cause damage to fruits. Any damage to fruit provides an entry to allow brown rot easy access to infect the fruit. Likewise, you should take care during harvest not to damage the fruit. Fruit should be stored in a cool environment to reduce rot spread in harvested fruit.
Please, please do NOT spray all in one fruit tree sprays on blossoms for brown rot control!
These sprays typically contain insecticides that are highly toxic to pollinators. They cannot be sprayed on your buds or blossoms without harming your bees. To achieve brown rot control you must spray your buds and open blooms with fungicides to get good brown rot control. Please do our struggling pollinators a favor and invest in a recommended fungicide and spray it by itself on your buds and blossoms.
In conclusion, if you are considering planting stone fruits, make sure you can commit to spraying your trees with a fungicide 3-12x a year. If you can’t we suggest you avoid disappointment and try planting a no/low spray fruit variety like the Asian persimmon. If you already have peach trees and are struggling to get fruit, we hope this helps you get your brown rot under control so that you can harvest fruit!
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