Blackberry Diseases

Thornless blackberry is a potential alternative crop for Central Florida. There are several pest problems a potential grower will encounter, especially diseases because of the warm, wet, humid conditions we experience. Profitable yields will not be achieved in the long run without control of these diseases. The Southeast Regional Caneberries Integrated Management Guide provides control measures for all pests.  Some of the most common diseases are below.

 Orange Felt
Early orange felt symptoms on blackberry cane are yellowish spots on the canes.

Early orange felt symptoms on blackberry cane are yellowish spots on the canes.

The disease I have seen most often affecting blackberries is Orange Felt, a parasitic alga. The advanced stage symptoms are fuzzy orange growth on the canes as seen at the top of the post. Very hot and humid conditions favor the growth of this alga that will girdle canes or stress the canes so that other diseases are made worse. Various practices can reduce the incidence of this disease: pruning to open up the canopy and permit faster leaf drying, a weed-free strip or plastic mulch under the canopy, avoiding plant stress, and avoiding poorly drained sites. Even with all these practices you are likely to see this disease, so be ready. Copper products do not show consistent or sufficient management of this disease. Phosphonate fungicides are the only ones which consistently suppress this disease on blackberries.

 

Cane Blight
Dead cane blight infected canes look silvery grey and are associated with large pruning cuts or wounds.

Dead cane blight infected canes look silvery grey and are associated with large pruning cuts or wounds.

This fungal disease, Leptosphaeria coniothyrium, also causes stem canker on roses and other ornamentals. The fungus overwinters on dead tissue like old floricanes or pruning debris. Spores produced spring through fall then infect wounded primocanes with the assistance of rainfall or irrigation. The pathogen grows in the primocane through the season and results in floricane bud failure and dieback in the spring. Watch for cane lesions that are dark red to purple with irregular purple borders. The fruiting structures look like small, black, pimple-like bumps buried in the tissue. Practices to reduce this disease include: avoid wounding primocanes, prune when at least four days of dry weather is expected, and pinch off the tips of primocanes rather than making severe cuts with shears. This may require more frequent pruning of primocanes, but the smaller wounds heal more quickly. Also remove infected canes and all old floricanes after harvest each year, cutting as close to the ground as possible and removing debris from the field. Practices similar to the ones to avoid Orange Felt are also useful. Apply fungicides after pruning to provide a protective barrier on wounds. More information.

Leaf Spots
Various leaf spotting fungi can attack blackberries.

Various leaf spotting fungi can attack blackberries.

Various fungal leaf spots, Cercospora, Pseudocercospora, and Septoria, attack blackberry. Be on the watch for these and apply fungicides to protect as soon as you see signs. See The Southeast Regional Caneberries Integrated Management Guide for more control information.

 

 

 

2 Comments on “Blackberry Diseases

  1. Hi!
    I live in Glenmont, NY just south of Albany.
    I have six Ouachita thornless blackberry bushes and some of the canes appear to have been infected with Orange Felt. My berry crop is just turning red so ripe berries should be arriving in a week or two providing the disease doesn’t take over all the canes. What would you recommend as a a treatment and when can I start without contaminating the berries if possible. Thank you for your support.

    • There is not much that can be done at this stage. It may cause defoliation that will impact the quality of your berries, but you will probably still be able to harvest. It needs to be controlled with phosphite type sprays early on as it starts to show lesions on the canes. Make sure you remove all the affected canes as soon as possible after harvest to reduce spores spreading to the primocanes. Prophyt is labelled with 0 days preharvest interval, so you could use this, directing it at the canes, but it is best used before or at the appearance of the disease.

Leave a Reply

Your email address will not be published. Required fields are marked *