Controlling phytophthora disease on pepper

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Phytophthora capsici attacks both bell and hot peppers in Michigan (view images). This devastating dis­ease can wipe out entire pepper fields, caus­ing enormous losses in yield and profit. Be­cause of the destructive nature of Phy­tophthora, researchers at Michigan State Uni­versity are dedicated to the knowledge and management of this disease. 

symptoms can be hard to spot on pepper, and infection may occur days be­fore any visible signs of disease appear. The most obvious symptom of Phytophthora in peppers is the wilting and death of plants. During times of high relative humidity and wetness, a layer of spores may cover the pepper like “powdered sugar.” Roots and crowns can potentially turn brown or black, and dark lesions will periodically appear on the skin of the fruit. 

Because of the severity of Phytophthora, early management is the best recommendation to prevent spread. Once a field has been ex­posed to Phytophthora, scout fields regu­larly for any signs of disease. It is possible to plant pepper varieties that are somewhat re­sistant to Phyophthora, or to plant a Phy­tophthora tolerant variety. 

Warm, wet weather is most conducive to the spread of Phytophthora. The disease can live in the field at least ten years, and is problem­atic for many vegetable crops. When plant­ing peppers, do not plant into a field rota­tion with other susceptible crops like tomatoes, zucchini, squash, cucumbers, beans, melons or pumpkins. Plant peppers into raised beds with black plastic and only in well drained sites. If irrigation is necessary, it is best to use drip irrigation and to not use surface water as a source of irrigation. One of the best defenses against Phytophthora is to spray fungicides early and often. It is important to make sure that there is ade­quate canopy coverage so that Phytophthora has no chance of infecting the plant. It is wise to rotate between fungicides so the pathogen 
does not build up immunity to any one fungicide.

When applying a foliar application of fungicide, it is important to keep spray intervals short. Make sure to apply the fungicide before a rain, and come back as soon as possible after a rain.

 If Phytophthora becomes a problem, harvest the fruit as early as possible and keep the harvested fruit in a cool, dry environment. Plow under the diseased portion of the field, and the healthy looking plants that border the area. View pdf of this article online at:

Products available for Phytophthora control on pepper


Active ingrediant

Ridomil Gold/ Ultra Flourish


Ridomil Gold Copper 

mefenoxam / copper hydroxide

ProPhyt / Phostrol 

phosphorous acid equivalents

Kocide, Champ / Cuprofix Disperss

copper hydroxide /copper sulfate




famoxadone + cymoxanil 

Acrobat / Forum


Dr. Hausbeck's work is funded in part by MSU's AgBioResearch.

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