Botrytis Blight: A Fungal Threat to Blueberry Crops

Botrytis blight, also known as gray mold, is a common fungal disease that affects blueberry plants worldwide. It is caused by Botrytis cinerea, a fungus notorious for infecting a wide range of crops, including strawberries, grapes, and tomatoes. The disease is most active in cool, wet, and humid conditions—typically during periods of prolonged rainfall or poor air circulation in dense canopies. When conditions are favorable, Botrytis can cause severe damage to blossoms, stems, and fruit, leading to significant economic losses for blueberry growers.

The disease usually begins during the flowering stage. As blueberry blossoms open, their corollas (petal tubes) age and become susceptible to infection. Ideally, the corolla should drop naturally after pollination, but if weather delays this process or if frost damages new growth, wounds may form that invite fungal invasion. Once infected, blossoms turn brown, shrivel, and often remain attached to the plant. Under humid conditions, they become covered with a characteristic gray, fuzzy mold.

Botrytis cinerea is an opportunistic pathogen that thrives on weakened or dying plant tissues. It survives in the environment as a saprophyte, feeding on dead leaves, pruned canes, or other plant debris. The fungus produces abundant spores that can easily spread through wind, rain, or mechanical contact during harvesting. Because spores are often present throughout the growing season, complete eradication is nearly impossible.

Symptoms of Botrytis blight vary depending on the infected plant part. Leaves may develop yellow spots that later turn brown and gray, while infected twigs can die back from flower blight. On ripening or stored berries, the disease manifests as soft, gray, moldy rot that causes fruit to shrivel and decay. Although postharvest fruit rot is common in regions where berries are stored for long periods, it is less of a concern in areas like Florida, where fruit moves rapidly from harvest to market.

Effective management of Botrytis blight involves maintaining good air circulation, removing dead plant material, and avoiding overhead irrigation. While sanitation alone cannot eliminate the disease, it remains an essential component of integrated fungal control strategies to protect blueberry yields and quality.
Botrytis Blight: A Fungal Threat to Blueberry Crops

Botrytis rot of blueberries

Botrytis rot (grey mold) is a fungus that grows at temperatures as low as 32°F, but growth is slow at this temperature. Following wet weather during mid to late bloom, individual blossoms or entire fruiting clusters will wither and die. The disease is not a problem during the summer months but can cause rotting of harvested fruit. It is believed that Botrytis blight is less of a problem where burning is used for pruning, and the disease can be managed with properly timed fungicide applications.

Botrytis blossom blight is an important disease of blueberries and several flowering ornamental plants. The fungus, Botrytis cinerea, most commonly infects and blights wounded or senescent plant tissues. As a blueberry bush blooms, corollas (the fused petal of the flowers) senesce and become quite susceptible to infection.

What are the symptoms? On leaves, brown, irregular lesions develop that sometimes distort leaves. Blighted blossoms turn brown and soon become covered with abundant gray mold. Infected twigs are first brown to black and later become tan to gray. Developing berries can also become infected, but fruit rot usually does not develop until after harvest. Infected berries become covered with a fluffy gray mold.

The fungus Botrytis cinerea causes a decay of ripening fruit. Infected fruit become covered with the typical gray, moldy growth of the pathogen. Botrytis also causes a stem canker which is similar to that caused by other fungi.

Botrytis rot of blueberries