Ripe Rot

Colletotrichum spp., with causal complexes varying among hosts

Ripe rot is a Colletotrichum-associated disease of grapes, blueberries, cranberries, coffee, peppers, and other fruit in which infections often remain latent until ripening. On grapes, berries develop circular reddish-brown lesions, soften, shrivel, and produce salmon or orange spore masses. Warm humid weather, frequent rain, dense clusters, and delayed harvest favor epidemics. Because the name is used across crops, the host and causal complex must be stated. The disease overlaps anthracnose and bitter rot biologically but should remain distinct where crop guides recognize ripe rot as a ripening-berry syndrome.

Identification

Confirm crop and ripening stage. On grape, lesions appear on colored berries, often with concentric salmon-orange acervuli and rapid shriveling. Blueberry and other hosts may show soft sunken decay without the same ring pattern. Collect intact fruit from early and advanced stages, portions of the cluster or pedicel, and any overwintered mummies. Keep samples cool and avoid sealing wet fruit in plastic. Culture and multilocus sequencing may be needed to resolve Colletotrichum complexes and distinguish ripe rot from bitter rot, anthracnose, Phomopsis, Botrytis, sour rot, and heat injury. Latent infection means symptom-free fruit may still carry the pathogen.

Symptoms / Signs

Small reddish, tan, or brown spots appear as fruit begins to soften or accumulate sugar. Lesions enlarge, become sunken, and exude pink, salmon, or orange spores under humidity. Berries may soften, leak, collapse, and dry into mummies. In a cluster, disease can jump among touching berries and attract insects or secondary yeasts. Postharvest symptoms may emerge during storage if fruit was infected before harvest and cooled slowly.

Life Cycle / Process

The fungi survive in mummified fruit, infected shoots, pedicels, crop debris, and sometimes asymptomatic perennial tissue. Conidia spread by splash throughout bloom and fruit development. Infections may remain quiescent until ripening changes fruit chemistry and defenses. Warm rain near veraison or harvest drives rapid symptom expression. Species composition varies among regions and crops, affecting temperature response and fungicide sensitivity.

Prevention

Remove mummies and diseased clusters, manage canopy density, and improve air movement around fruit. Avoid overhead irrigation near ripening, control insects and cracking, and harvest promptly at suitable maturity. Sanitize picking containers and packing lines and cool fruit rapidly. Use clean planting material and resistant cultivars where available. Preventive fungicides must be timed before infection according to the crop-specific guide; post-symptom sprays will not restore fruit.

Management / Control

Cull symptomatic clusters or fruit and keep them out of packing and storage. Shorten harvest intervals during warm rainy periods and segregate high-risk blocks. Confirm the causal complex when standard programs fail, then review bloom-to-harvest coverage, canopy penetration, resistance management, and sanitation. Maintain commodity-appropriate refrigeration and avoid condensation. Do not label all Colletotrichum fruit rot as ripe rot without the crop context, and do not transfer grape recommendations to blueberries, peppers, or coffee.

Procedure Steps

1. Record crop, cultivar, fruit maturity, block, rainfall, and harvest or storage timeline. 2. Photograph early lesions and colored spore masses before berries collapse. 3. Collect intact clusters or whole fruit across stages plus mummies or infected shoots; keep cool and dry. 4. Differentiate from Botrytis, sour rot, bitter rot, anthracnose, and physiological breakdown. 5. Cull affected fruit, tighten harvest and cooling, remove inoculum, and revise crop-specific preventive timing.

Safety Notes

Do not consume or market visibly rotted fruit. Mixed secondary molds, yeasts, and insects may create food-quality and worker-exposure concerns. Use gloves during culling, sanitize food-contact surfaces with approved products, and observe all preharvest and reentry intervals.