Brown Rot

Monilinia spp.

Brown rot is a major blossom, twig, and fruit disease of peach, nectarine, plum, cherry, apricot, and other stone fruits. Monilinia species infect flowers during wet bloom, cause blossom blight and twig cankers, and later rot ripening fruit. Fruit lesions expand rapidly as soft brown decay covered by tan or gray spore tufts, often in concentric rings. Infected fruit shrivels into mummies that remain in the tree or on the ground and carry inoculum. Warm wet weather, hail or insect wounds, fruit contact, and delayed cooling create severe preharvest and postharvest losses.

Identification

Inspect blossoms for sudden browning that remains attached and shoots for short cankers below killed flowers. On fruit, look for rapidly expanding soft brown rot and powdery tan spore pads. Mummified fruit are a strong orchard clue. Submit fresh blossoms with attached spur tissue, active twig cankers, and whole fruit at early lesion stages. Culture, microscopy, or molecular assays can separate Monilinia from Rhizopus, Botrytis, Colletotrichum, and other fruit rots. Different Monilinia species and resistance profiles may matter commercially. Do not diagnose from brown fruit alone if storage breakdown or injury could explain decay.

Symptoms / Signs

Flowers wilt, turn brown, and cling to twigs; gum may form at infected spurs. Short shoots die back from blossom infections. Fruit develops a small brown spot that enlarges within days, softening the flesh and producing tan-gray spore clusters. Adjacent fruit in tight clusters infect one another. Rotted fruit may fall or dry into hard black mummies. Latent infections can become visible during ripening, packing, transit, or retail display.

Life Cycle / Process

The fungus survives in mummified fruit and infected twigs. In spring, these tissues produce spores that infect blossoms during wet weather. Secondary spores from blighted flowers and young fruit spread through rain, insects, and contact. Fruit susceptibility rises near ripening, especially after cracking, hail, insect feeding, or handling wounds. Mummies formed after harvest or left in the canopy bridge seasons.

Prevention

Remove mummies from trees and ground, prune cankered shoots during dry weather, and thin fruit to reduce contact. Control insects and avoid injuries. Manage canopy density and irrigation to shorten wetness. Harvest carefully, sanitize containers, and cool fruit rapidly. Use resistant cultivars where locally suitable. Commercial fungicide protection is timed to bloom and preharvest risk stages and must follow current stone-fruit labels and resistance-management programs.

Management / Control

Remove blighted blossoms, cankered shoots, and rotting fruit before they become major spore sources. Separate diseased harvest lots and discard affected fruit; fungicides cannot cure visible decay. Review bloom sprays, preharvest coverage, rainfall, insect damage, and sanitation if losses recur. Rotate effective FRAC groups because Monilinia resistance can develop. Maintain the cold chain and minimize packing injuries. Home growers should prioritize sanitation and canopy management rather than repeated unscheduled spraying.

Procedure Steps

1. Inspect at bloom for attached brown flowers and short twig cankers, then rescout as fruit colors. 2. Photograph spore pads, fruit clusters, mummies, and any wound associated with infection. 3. Collect whole early-stage fruit, blossoms with spur tissue, and short cankered twigs; keep cool. 4. Differentiate from Rhizopus, Botrytis, anthracnose, and physiological breakdown. 5. Remove inoculum, protect susceptible stages using labeled guidance, and strengthen harvest sanitation and cooling.

Safety Notes

Do not eat moldy stone fruit or feed heavily decayed fruit to animals. Secondary molds and decay products may create hazards beyond Monilinia. Observe preharvest intervals, reentry restrictions, and label limits for edible crops; use eye protection when pruning overhead.