Why Are My Blackberries Drying Up on the Plant?

Blackberries that begin to develop normally but then dry out, shrivel and brown on the cane before they ripen are experiencing one of several problems that cut off the water and nutrient supply to the developing fruit. Identifying whether the drying is accompanied by grey fuzzy mould, small grubs inside the fruit, or simply drought conditions points you toward the correct cause.

Grey mould (Botrytis)

Botrytis cinerea infects blackberry flowers and developing fruits during wet conditions. Affected fruits develop a brown, water-soaked appearance, become covered in grey-brown fuzzy fungal growth, and dry to a papery brown shell. The infection starts at the stalk end of the fruit cluster and progresses through the cluster. Remove all infected fruit material immediately. Improve air circulation through the cane structure by opening up the training and removing excess canes. Avoid overhead watering that keeps fruit wet.

Raspberry beetle larvae

The raspberry beetle (Byturus tomentosus) lays eggs on flowers in June–July. The hatching larvae bore into the developing fruit and feed on the flesh and seeds. Affected fruits often show a small entry hole, may shrivel and dry prematurely, and cutting one open reveals a small white grub. There is no treatment for larvae already inside fruit. For the following year, apply an approved insecticide (pyrethrum or thiacloprid) at first pink bud stage — before the flowers open. Pheromone traps may also be used.

Drought during fruit development

In very dry conditions, small or poorly irrigated plants may shed developing fruits or allow them to dry rather than devoting scarce water to ripening them. This tends to affect fruit throughout the plant uniformly rather than in the clustered, progressive pattern of disease. Water deeply and mulch around the base of the plant to maintain soil moisture through July and August.