Boll Rots of Cotton
Published: 08/29/2023
Cotton boll rots are caused by numerous fungi and bacteria such as Fusarium spp., Phytophthora spp., and Xanthomonas citri pv. malvacerarum. Identifying the primary pathogen is difficult due to multiple saprophytic (not disease-causing) fungi on rotten bolls. Yield losses are greater with frequent rainfall and dense crop canopies.
Fusarium boll rot is the most common boll rot in the U.S., causing bolls to turn brown to black with pink or orange conidial masses under humid conditions. Phytophthora boll rot shows soft, watery, black rot symptoms, while Xanthomonas boll rot starts as small, circular, water-soaked lesions that turn black when dry. Seed from infected bolls are likely to carry bacteria that can impact the subsequent crop.
Cotton boll rot.
Travis Faske
Cotton boll rot in plant canopy.
Travis Faske
Managing plant growth, using pathogen-free seed, and controlling insects can reduce the impact of boll rots. Fungicide applications have limited efficacy in managing boll rots.
Written and reviewed by Travis Faske, University of Arkansas; Tom Allen, Mississippi State University; and Trey Price, Louisiana State University.
Cotton boll rot. Image by Travis Faske.
Cotton boll rot in the plant canopy. Image by Travis Faske.
Cotton boll rot. Image by Clemson University, USDA Cooperative Extension Slide Series, Bugwood.org.
Cotton boll rot. Image by Clemson University, USDA Cooperative Extension Slide Series, Bugwood.org.
Gallery images courtesy Travis Faske and Clemson University, USDA Cooperative Extension Slide Series, Bugwood.org.
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