EPIDEMIOLOGY OF THE BOTRYOSPHAERIA DOTHIDEA CANE CANKER DISEASE OF THORNLESS BLACKBERRY

Botryosphaeria dothidea causes a serious cane canker disease of thornless blackberry in the eastern United States.
New cankers usually appear in early spring, although some can be found in late fall or early winter.
These cankers are usually associated with lateral buds and subtending leaf petiole scars.
B. dothidea was isolated from 6–9% of symptomless buds and petiole scars in fall and spring.
This organism was recovered from only 0.3% of the internal tissue of symptomless buds.
Some cultivars tend to retain leaf petioles for varying periods of time following leaf senescence and leaflet abcission in late fall.
B. dothidea was isolated from 20–100% of these persistent petioles, depending on cultivar and degree of leaf senescence.

Although inoculation studies show that thornless blackberries are highly susceptible to B. dothidea, various levels of field resistance have been observed among cultivars.
A consistent correlation was not found between degree of resistance and retention of petioles into late winter; however, cultivars with high disease incidence levels in field plots also tended to retain a high percentage of petioles into winter.
In addition, recovery of B. dothidea from persistent petioles correlated with degree of canker incidence of the respective cultivars.
Data suggest that B. dothidea may aggressively colonize senescing leaf petioles and, once established saprophytically, invade healthy cane tissue.

IV International Rubus and Ribes Symposium

John L. Maas

https://doi.org/10.17660/ActaHortic.1986.183.17