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Treat blackberry for possible anthracnose? #876308

Asked July 08, 2024, 11:09 AM EDT

About a third of my blackberry plants seem to be suffering from anthracnose. Some of the berry druplets are dry/brown. The plants are overall in distress, too. Some entire berries shriveled instead of maturing. Other blackberry plants about 6-8 feet away look fine/normal. All of the patch gets same watering and amount of sun. Is there treatment to save the affected plants? or should I be ripping them out to avoid them affecting others? There are plenty of new canes. Does the 'infection' affect the entire plant, or just floricanes? Is the soil likely infected, too?

Howard County Maryland

Expert Response

Hi- anthracnose and cane blight are common diseases of blackberry plants in MD. If the cane and fruit symptoms are widespread you may want to consider removing all plants. If the symptoms are more limited, prune out, bag, and discard all symptomatic canes (don't let the prunings touch the ground).
These diseases infect floricanes and primocanes. They don't live in the soil but overwinter on infected plant parts.

Liquid lime sulfur is a low-risk "organic" fungicide labeled for use in the dormant season that can help control both diseases.

References:
https://plantpathology.ca.uky.edu/files/ppfs-fr-s-17.pdf

https://ohioline.osu.edu/factsheet/plpath-fru-27

https://extension.uga.edu/publications/detail.html?number=C894&title=cane-blight-of-blackberry

https://extension.umd.edu/resource/growing-raspberries-and-blackberries-home-garden/

https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/456/456-018/ENTO-567-C.pdf
Jon

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 July 08, 2024, 12:08 PM EDT

Thanks for such quick response. Okay, I'll be cutting out and remove/bag affected or suspected canes.

I have to read up on the references you provided for fungicide that could be appropriate now for the other plants (not showing trouble yet.)

Richard

On Monday, July 8, 2024 at 12:08:41 PM EDT, Ask Extension <<personal data hidden>> wrote:

The Question Asker Replied July 08, 2024, 12:25 PM EDT

Hi- Immunox (myclobutanil) is labeled for controlling anthracnose in cane fruits. It is widely available. If you can't find liquid lime sulfur for a dormant spray you can use copper sulfate or Bordeaux which may be easier to find locally.

These diseases are encouraged when air circulation around canes is reduced due to overcrowding and failure to head back primocanes and laterals.
Jon

Thanks! I'll check on those fungicides.

Thanks, also, for info about air circulation. As I tried to 'get the most berries' from my area I have allowed too many new plants/shoots, so it's denser than ideal.

I always trim back tips of primocanes. Some long laterals, too.

On Monday, July 8, 2024 at 12:48:53 PM EDT, Ask Extension <<personal data hidden>> wrote:

The Question Asker Replied July 08, 2024, 12:53 PM EDT

I was able to find Bonide brand of fungicide with copper octanoate. The label describes okay for blackberries and raspberries "... from dormant up until harvest". I wouldn't want to eat fruit that had been recently sprayed, but perhaps the plants overall can be helped by applying now instead of waiting until March.

This USDA.GOV document lists many copper variants.

https://www.ams.usda.gov/sites/default/files/media/Coppers%20fixed%20TR%202011.pdf

Do you have advice on effectiveness of copper octanoate for use on mid-season berry plants? I've already cut/removed canes that seemed sick.

I know plants get stressed with extreme heat. Spray very early in the morning? or at dusk?

Thanks,

Richard

The Question Asker Replied July 09, 2024, 9:13 AM EDT

Hi- copper fungicides can help prevent the spread of diseases like cane blight and anthracnose. Copper octanoate should be fine to use. We don't have any research data on its particular effectiveness against cane and leaf diseases of blackberry.

Spray early or late in the day to minimize the risk of leaf burn. Good coverage of all leaf surfaces and stems is essential.
Jon

Thanks. Got it.

On Wednesday, July 10, 2024 at 08:29:18 AM EDT, Ask Extension <<personal data hidden>> wrote:

The Question Asker Replied July 10, 2024, 8:56 AM EDT

Treat blackberry for possible anthracnose? #876308

Expert Response

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