Choanephora fruit rot on yellow straight neck squash (Cucurbita pepo) caused by Choanephora cucurbitarum. This disease, also known as "wet rot" and "blossom end rot," can destroy many blossoms and fruit during extended periods of damp weather.
Photograph courtesy Gerald J. HolmesDept. Plant Pathology, North Carolina State UniversityBox 7616, Raleigh, NC 27695
Choanephora fruit rot is favored by warm (>25°C), wet weather. Both blossoms and fruit are affected and fruit nearest the ground are more likely to become diseased. It is not unusual to find 30–40% of blossoms and/or fruit infected with the fungus. While the disease is destructive, it is also as short-lived as the conditions that promote it. Subsequent fruit sets are usually not affected unless conducive conditions reoccur. The fungus resembles Rhizopus stolonifer, but spore-bearing heads are branched, a feature that can be seen with a 20× hand lens.
Under optimal conditions, squash fruit can develop from flower to marketable fruit in 1 to 2 days. Rapid fruit development and the ephemeral nature of the disease and the conditions that promote it make control measures impractical. The disease is also common on pumpkin, okra, snap bean, and southern pea. This photograph was taken in the fall, 1997, in Johnston County, North Carolina (GPS coordinates: 35°16.06N 078°23.64W).
APS publication number: IW00007
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