Dothiorella canker

Symptoms typically start as small, discolored areas on the bark, which eventually expand into dark brown or black sunken cankers.

As the infection progresses, the affected bark may crack or peel away, exposing the underlying woody tissue to environmental stress and secondary invaders.

The appearance of numerous small, pimple-like structures (pycnidia) on the surface of the canker is a characteristic sign of active sporulation.

Foliage on infected branches often exhibits yellowing, chlorosis, and premature senescence, followed by the dieback of the branch starting from the tip.

In many cases, the affected area produces gum or resinous exudate as a defense mechanism, which further serves to identify the site of infection.

The disease is caused by the fungus Dothiorella gregaria, which belongs to the family Botryosphaeriaceae, often associated with the sexual stage Botryosphaeria dothidea.

This pathogen acts as a facultative parasite, primarily infecting the bark and cambium layer of woody host plants, leading to localized or systemic necrosis.

The fungus produces pycnidia, which are asexual fruiting bodies that emerge through the bark surface to release conidia during periods of high humidity and rainfall.

Transmission occurs through wind, water splashes, and insect vectors, facilitating the spread of the pathogen across the orchard or forest area.

The fungus is capable of persisting in dead plant tissue and bark for several years, allowing it to re-infect healthy tissue whenever environmental conditions become favorable.

Dothiorella development is highly favored by environmental stress, particularly heat and water deficit during the growing season.

Trees with existing mechanical injuries, sunscalds, or winter freeze damage are significantly more susceptible to successful fungal colonization.

Poor orchard sanitation, such as leaving diseased pruning debris on the orchard floor, acts as a primary reservoir for the inoculum.

Dense tree canopies that restrict airflow increase the duration of surface wetness, creating ideal conditions for spore germination on the bark.

Nutrient deficiencies, particularly when plants are grown in unsuitable soil conditions, weaken tree vitality and make them easier targets for the pathogen.

The disease affects a wide range of economically important trees, including apples, pears, peaches, apricots, walnuts, and various ornamentals.

Severe infections can lead to the loss of entire scaffolds or structural branches, significantly reducing the productive life of the tree.

When the main trunk is girdled by a large canker, the entire tree can suffer from sudden wilting and eventual death, causing significant economic loss.

Fruit quality is often compromised, leading to post-harvest decay if the fungus invades the fruit tissue through pedicels or other points of entry.

Chronic infections lead to a gradual decline in tree vigor, making the orchard more prone to secondary pests and unfavorable climate impacts.

Management focuses on rigorous sanitation by pruning out and destroying all infected wood to reduce the local population of the fungus.

• Use sharp, sterilized tools when pruning to prevent accidental transmission of spores.
• Apply protective whitewash to trunks to prevent sunscald injuries.
• Seal large pruning wounds to prevent entry points for the pathogen.
• Schedule fungicide applications targeting early-season spore dispersal periods.

Maintaining optimal tree vigor through balanced fertilization and appropriate irrigation is essential to help the plant resist infection.

In cases of localized cankers, surgical removal (excising) the infected bark tissue back to healthy, green tissue is a common remedial practice.

Integrated pest management strategies should be employed to control wood-boring insects that often assist in the movement of the fungus.