Peach Brown Rot & Related Insect Control
What are the latest, best spray materials and procedures to control Peach Brown Rot and related insects so that a healthy crop can be harvested? Sulfur and continuous sanitary cleanup with pruning has shown some improvement, but fruit tree spray and Neem oil among others, have not. This year I started with over 100 fruit on the tree, but with normal fruit drop and my removal of visually browning fruit, the last single peach also started to show a filling and growing circle of brown rot. It was within the last month of ripening, but it still had hard and white flesh with a greenish tint and no yellow ripening yet. Insects seem to love it anyway and the center of the brown circle had a puncture. It wasn't clear whether the insect bite started the rot or whether the rot started first. My treatments have apparently also allowed little or no twig brown rot compared to last year. Please advise. Norm
New Castle County Delaware
This season has been favorable for brown rot caused by the Monilinia fungus due to the wet weather. The fungus overwinters in mummies formed the previous season, in blighted twigs, and in cankers. Conidia produced on mummies (old dried infected fruit in the tree) and twig cankers are the more common source of spores for blossom infections in the spring. An additional source of spores is from mummies that have fallen on the ground, so sanitation is very important.
The first fungus spores are formed about the time the blossoms begin to open. Environmental conditions are important for the development of the disease. Warm, wet, or humid weather is very favorable for disease development. The severity of brown rot increases as the fruit ripens. Wounded fruit are more susceptible to infection, so your insect control is important.
There are combo fruit tree sprays that contain fungicide and insecticide, but in weather such as we had this spring and summer, you may need to spray every 10 days from late bloom onward. Be careful of bee activity, and spray at dusk.
Research at Rutgers has shown that timing brown rot sprays 18 days, 9 days, and 1 day before harvest provided greater than 95 percent control under heavy disease pressure. When following this regime, be sure to rotate chemistries by FRAC Group Code number for resistance management. Fontelis, Topsin, Tilt and Captan are good choices to rotate with, but you need a pesticide license and need to apply according to the label. Homeowner choices are more limited. See the Penn State publication: http://extension.psu.edu/plants/tree-fruit/news/2017/managing-fruit-rots-this-season
Thank you for contacting Cooperative Extension,
Thank you for your educational response. I will proceed to the Penn State Pub next.
Although I haven't found Immunex or Fruit Tree and Plant Guard locally ,recommended as Excellent for brown rot by the Maryland previously posted reference, the latter containing insecticide as well, I find the timing a little confusing:
1. With insecticides,if they must not be applied while any blossoms are still present to avoid harming bees, this leaves the initially starting fruits susceptible as I have seen tiny apple tree fruits tapped.How can that be controlled? Would Neem oil be an appropriate fill in? 2. The products recommend 7-10 day intervals, but only 5-7 applications maximum and insecticides stopped 14 days before harvest. If Rutgers applications meant sequentially 18, 9,and 1 day before harvest, then only 4 applications are needed for the fungicides, but other required insecticide apps are still necessary. What is recommended? 3. I don't understand your FRAC Coded procedures.
How you proceed really hinges on whether you are a home gardener or have a commercial fruit operation and a commercial pesticide certification. Many products are only available to certified applicators.
For protecting bees, products must go on late in the day when bees have returned to the hives. You are correct that fungicides need to be applied when trees are in bloom to protect against the brown rot fungus. Fungicides are not as hazardous to bees, but care must still be taken. I usually recommend that protectant fungicides be applied right before flower buds open, before bees are active in the spring, and then at petal drop, when flowers have been pollinated. Those are times of lower bee activity. That is also why sometimes the combo sprays are convenient but not always the best choice for good protection against insects and diseases, while protecting bees. Neem oil is a good safe choice, but not as effective.
I mention the FRAC codes because you do not want the fungi to develop resistance to the fungicides or you will loose the ability to control them. In essence the fungicides will no longer be effective if you use the same one time after time. It is suggested that you rotate the chemicals you use, based on their type of chemistry (FRAC codes). You can use an older general products such as sulfur and captan without fear of resistance development.
Each product for disease and insect control is different and each has specific label directions for use which must be followed by law.