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Publication #PP-148

2014 Florida Citrus Pest Management Guide: Brown Rot of Fruit1

J.H. Graham, L.W. Timmer and M.M. Dewdney2

Management of brown rot, caused by Phytophthora nicotianae or P. palmivora, is needed on both processing and fresh market fruit. While the disease affects all citrus types, it is usually most severe on Hamlin, Navel, and other early maturing sweet orange cultivars. See also PP-156 Phytophthora Foot Rot and Root Rot for information on other Phytophthora diseases.

Phytophthora brown rot is a localized problem, usually associated with restricted air and/or water drainage. It commonly appears from mid-August through October following periods of extended high rainfall. It can be confused with fruit drop from other causes at that time of the year. If caused by P. nicotianae, brown rot is limited to the lower third of the canopy because the fungus is splashed onto fruit from the soil. P. palmivora produces airborne sporangia and can affect fruit throughout the canopy.

Early season inoculum production and spread of Phytophthora spp. are minimized with key cultural practice modifications. Skirting of the trees reduces the opportunity for soil-borne inoculum to contact fruit in the canopy. The edge of the herbicide strip should be maintained just inside of the dripline of the tree to minimize the exposure of bare soil to direct impact by rain. This will limit rain splash of soil into the lower canopy. The remaining blocks with overhead irrigation should be converted to undertree microsprinklers to avoid the promotion and spread of inoculum within the canopy. Boom applications of herbicides and other operations dislodge low-hanging fruit. Trees affected by Huanglongbing (HLB; citrus greening) are prone to prematurely drop fruit. These fruit on the ground become infected and produce P. palmivora inoculum. The sporangia can infect green fruit and result in brown rot infection in the canopy as early as July while fruit are still green. The beginning of the epidemic is very difficult to detect before the fruit are colored and showing typical symptoms. Application of residual herbicides earlier in the summer may reduce the need for post-emergence materials later and minimize fruit drop throughout this early stage of inoculum production from fallen fruit.

Usually a single spray application of Aliette, Phostrol or ProPhyt before the first signs of brown rot appear in late July is sufficient to protect fruit through most of the normal infection period. No more than 20 lb/acre/year of Aliette should be applied for the control of all Phytophthora diseases. Aliette, Phostrol, and ProPhyt are systemic fungicides that protect against postharvest infection and provide 60-90 days control. Copper fungicides are primarily protective but are capable of killing sporangia on the fruit surface and thus reducing inoculum. They may be applied in August before or after brown rot appearance and provide protection for 45-60 days. If the rainy season is prolonged into the fall, a follow-up application in October of either systemic fungicides at one-half of the label rate or copper may be warranted. With average quality copper products, usually 2-4 lb of metallic copper per acre are needed for control.

Precautions should be taken during harvesting to exclude brown rot-affected fruit in the field containers because a few pieces of affected frut can result in rejection of the entire container at the processing or packing facility.

Recommended Chemical Controls


See Table 1.

Rates for pesticides are given as the maximum amount required to treat mature citrus trees unless otherwise noted. To treat smaller trees with commercial application equipment including handguns, mix the per acre rate for mature trees in 250 gallons of water. Calibrate and arrange nozzles to deliver thorough distribution and treat as many acres as this volume of spray allows.


Table 1. 

Recommended Chemical Controls for Brown Rot of Fruit




Mature Trees


Aliette WDG


5 lb



4.5 pints



4 pints

copper fungicide


Use label rate.

1Lower rates may be used on smaller trees. Do not use less than minimum label rate.

2Mode of action class for citrus pesticides from the Fungicide Resistance Action Committee (FRAC) 2013. Refer to ENY-624, Pesticide Resistance and Resistance Management, in the 2014 Florida Citrus Pest Management Guide for more details.



This document is PP-148, one of a series of the Plant Pathology Department, UF/IFAS Extension. Original publication date December 1995. Revised September 2013. Visit the EDIS website at


J.H. Graham, professor, Soil and Water Science Department, L.W. Timmer, professor emeritus, and M.M. Dewdney, assistant professor, Plant Pathology Department, Citrus REC, Lake Alfred, FL; UF/IFAS Extension, Gainesville, FL 32611.

The use of trade names in this publication is solely for the purpose of providing specific information. It is not a guarantee or warranty of the products named, and does not signify that they are approved to the exclusion of others of suitable composition.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.