By Megan Dewdney
It is late summer or early fall, and the usual time to consider brown rot treatment options has passed. However, you smell a sharp fermented fruit odor. When you look closer, fruit have the telltale soft brown lesions of brown rot. What options exist to minimize losses now?
Photo by Tonya Weeks
It is too late for the traditional control options like phosphite applications [Fungicide Resistance Action Committee (FRAC) code P 07] to be effective quickly as they primarily stimulate the tree defenses.
Copper applications are a possibility with the advantage of killing the inoculum that forms on the outside of the fruit. Protection is generally between 45 to 60 days, but the copper may need reapplication at a half rate if there has been greater than average rainfall.
Other products that can work well in the later season are Orondis Ultra (FRAC codes 40+49) and Revis (FRAC code 40). See rates and usage patterns in the Florida Citrus Production Guide brown rot chapter. These products work well in the late season and protect fruit for at least 30 days. It is important to rotate fungicide modes of action between any root rot/foot rot treatments and brown rot treatments.
The phytophthora diseases are all related. The phytophthora root propagule count is indirectly related to brown rot. But if your counts are high, you are more likely to have brown rot on cultivars at color break. Dropped fruit attract zoospores which infect and sporulate quickly. The new sporangia and zoospores then get splashed into the canopy.
As a reminder, both Phytophthora palmivora and P. nicotianae can cause brown rot. P. palmivora is a greater concern for the disease because of its ability to splash from fruit to fruit, causing infection all the way to the top of the canopy. However, P. nicotianae can be very destructive in unskirted trees, although infection stops at approximately 3 feet above the soil.
Megan Dewdney is an associate professor at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.
Share this Post
Sponsored Content