Botryosphaeria dieback in walnut orchards is particularly troublesome this year, according to University of California researchers.
Beginning earlier this summer a Tulare County walnut grower noticed severe dieback in his walnut orchard. Symptoms included dead branches on otherwise healthy trees. In one example an entire tree appeared dead. Other symptoms included shriveled walnuts with small spots on the outer skins.
The grower contacted Elizabeth Fichtner, a Tulare County farm advisor with the University of California who specializes in orchard systems, including nuts, olives and dry plums.
Fichtner took tree samples and had them tested at the University of California’s Kearney agricultural research station. The samples tested positive for scale, which opened up the trees to Botryosphaeria, Fichtner said.
From that Fichtner recommended that the grower and his professional crop advisors apply fungicide and pesticide treatments to the orchard.
These are some sample photos from Fichtner’s visit to the orchard.