Bud rot, a destructive condition that affects the dense flowering structures of many plants, is caused by the widespread fungus Botrytis cinerea. This pathogen is commonly referred to as gray mold. Learning to identify the problem early is crucial for plant safety and yield preservation, as the infection typically begins deep inside the flower before becoming externally obvious. Quick detection is the best defense against total loss.
Identifying Early Symptoms
The initial signs of bud rot are often subtle, as the infection typically starts near the stem deep within the dense flower structure. One of the first visual cues is the premature browning or yellowing of small sugar leaves or bracts that poke out from the bud. Unlike the natural fading of a healthy plant, this discoloration appears in isolated spots and indicates tissue death at the core of the flower.
When gently squeezed, an infected area will feel softer or mushy compared to the firm structure of a healthy flower. This texture change is a direct result of the fungal mycelium breaking down the internal plant cells. Another early indicator is a distinctive, subtle change in odor, often described as a damp, musty, or moldy smell that is noticeably different from the plant’s natural aroma.
Progression to Advanced Mold and Slime
Once the Botrytis cinerea infection has taken hold, it spreads internally. The rot moves from the inside of the flower outward, causing the internal stem and core structure to collapse and turn a dark brown or black color. This internal decay is what leads to the characteristic “bud rot.”
As the infection progresses, the classic sign of “gray mold” begins to appear on the exterior of the dead tissue. This is the fuzzy, dusty-looking growth, which is actually the fungus’s mycelium and sporulation structures called conidiophores. The color is typically a dusty gray or brownish-gray, and it signifies that the fungus is actively producing and releasing millions of airborne spores. At this advanced stage, the infected area often becomes wet, slimy, and easily falls apart when touched.
Environmental Conditions That Encourage Bud Rot
The Botrytis cinerea fungus is widespread, but its spores only germinate and attack the plant when conditions are favorable. High relative humidity and poor airflow around the plant canopy encourage bud rot. Humidity levels consistently above 50 to 60% create the moisture needed for the fungal spores to germinate and penetrate the plant tissue.
Cooler temperatures, particularly during the nighttime hours, increase the likelihood of condensation forming on the plant surfaces. Lack of proper ventilation allows for stagnant air pockets, which trap moisture within the dense flower structures and create a microclimate ideal for fungal growth.