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Thornless Blackberry Fungus? #751351

Asked May 21, 2021, 4:45 PM EDT

These plants are ~40’ away from the sick raspberries. These leaves start with orange along the edges. It eventually covers most/all of the leaf, appearing to me like individual colonies of a fungus. My neighbor’s garden is heavily infected, mine is just starting to be.

Howard County Maryland

Expert Response

This looks like orange rust, a fungal disease and it looks severe. This is a systemic disease that infects blackberry and black raspberry. The plants need to be removed including the roots. Dispose of in the trash and do not compost. See more on our webpage https://extension.umd.edu/resource/raspberry-and-blackberry-diseases

Marian

Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied May 24, 2021, 10:51 AM EDT

Marian, Thank you for your response. I have some other questions.

1) Will this disease infect asparagus? They're in the same bed. (I have green and purple asparagus. Don't remember the names of the species.) Some of the infected blackberry plants spread from my neighbor's plot--and he and his neighbor are also infected. We're in a community garden and a number of other plots are also infected. We're all in full sun.

2) Are there other approaches? Some of these plants are 5-10 years old and VERY large. Cutting them back or using chemicals might be acceptable, but asking folks to dig them up is quite problematic.

3) Will this disease spread to raspberries? (Your website indicates that it won't.) I sent a different question to the Extension the same day about my raspberries. They have small brown spots, then the leaves die. It eventually kills the plants. I sent pictures of them, too. The blackberry plants with orange rust don't die. Just spread it.

4) Will this spread to other species of plants? If so, how do I sterilize the soil to prevent losing the whole garden?

Thank you again,

Betty

On Mon, May 24, 2021 at 10:51 AM Ask Extension <<personal data hidden>> wrote:

The Question Asker Replied May 24, 2021, 1:24 PM EDT

The rust that affects black raspberries and blackberries will not infect asparagus. Red raspberries are immune.

The fungus may not kill the plant outright but will weaken it considerably. You could prune all canes back to the ground and see if new canes get re-infected next spring. (They probably will because there is so much innoculum in the community garden). The rust may have come from adjacent natural areas with wild blackberry. Preventative fungicides (synthetic) would help but this may not be possible in the community garden.

This will not spread to other plant species and you do not need to sterilize the soil. Each type of rust has its own distinctive symptoms and its own specific plant hosts. For example, there are different types of rusts that can infect vegetables, fruits, ornamentals, grains & turf. Many rusts have complicated life cycles that include different spore stages at different times of the year & 2 or more different hosts. Other rusts produce only 1 type of spore or occur in all spore stages on one kind of plant. It is important to identify the plant and its susceptibility to disease. Look for rust resistant varieties if possible.

Marian

Thornless Blackberry Fungus? #751351

Expert Response

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