Reason for Concern:
1) Berries with dry cells are not accepted into more lucrative individual quick-freeze (IQF) markets.
2) Widely found in 'Marion' and 'Kotata' with minor amounts in 'Boysenberry'.
3) Occurs in both alternate-year and every-year fields.
4) Causal agent is unknown though recent theory is large Box Elder Bug populations during fruit ripening can result in deformed druplets due to feeding.
Individual drupelets shrivel, dry and harden, while small, scabby lesions may also form on drupelets. Affected drupelets may be widely scattered or clustered on the berry. Symptoms occur from early berry development to ripening. There has been some recent discussion that high populations of Box Elder Bug can feed on drupelets by sticking their probuscuses (long, thin feeding tubes) into individual drupelets. These damaged drupelets then take on secondary infection causing shrunken, brown, scabby lesions on the individual dropelets. Sporulation (spore reproduction) is not always visible. Many common fungi found on various blackberries, associated with dry drupelets, produce other, more recognizable symptoms. Such fungi cause Anthracnose, Ascosporic Dieback, Spur Blight, Cane and Leaf Rust, and Botrytis Fruit Rot. Other fungi of unknown pathogenicity also have been found. In general, the dry drupelets have not been found to be associated with downy mildew, sunburn, or pests such as the dry-berry mite.
Symptoms most often occur when late spring rains are numerous and frequent.
- As fruit ripens, affected fruit will have individual or clustered drupelets that will shrivel, dry, harden, and turn tanish in color.
- Since no single causal agent has been identified as the cause for these symptoms, there are no effective treatment measures or thresholds for economic damage to the crop.