Suspected Orange Rust on Blackberry plant

Asked August 21, 2020, 4:41 PM EDT

Hello,

I suspect my Ebony King thornless blackberry plant has orange rust. When pruning the new growth i have noticed the leaves have small holes that seem to be worsening. Today, i noticed small dots of an orange yellow substance on the underside of some of the leaves. I have done some research online but am not confident in self diagnosing my blackberry plant. I have attached a few images showing the leaf damage as well as the yellow orange dots. In addition, there is an image of the root area. I have labeled the new canes 1 & 2, the cane labeled 3 is the currently bearing fruit.

I appreciate any help in identifying the issue and any possible treatments that may be used. I have read that i may need to remove the entire plant and will not be able to replant blackberries there for a number of years.

Thank You
K. Baker

Nassau County New York

2 Responses

Hello and thank you for contacting us. You did not indicate what type of blackberries you have. The invasive Himalayan berries and the evergreen types are much more susceptible to blackberry rust than other types.

It is difficult to diagnose problems from photographs, but I can see that there are some signs of possible rust infection. It looks to be very slight if that is the case. I do not think the holes in the leaves are from rust, but more likely from insects; however, this too is not severe.

Here is a link with photos and information about blackberry rust. It includes recommended control measures. Sanitation (clean-up infected debris) and periodic spraying are the main controls. (Please note that the sprays listed under Chemical Controls are directed towards commercial producers, not gardeners.)
https://pnwhandbooks.org/plantdisease/host-disease/blackberry-rubus-spp-blackberry-rust

Rusts and other fungal diseases are always present and tend to flare up when the climatic conditions are right. So your goal should be to minimize these episodes since they cannot be totally eradicated once an infection is established.

Hello again,

My apologies but I mistakenly answered your question thinking you were on the other side of the country where orange rust is almost non-existent. I see that you did identify your blackberry as Ebony King.

Orange rust is a more serious variety of fungal disease. The recommendations from Cornell University indicate:

To control orange rust begin by planting only healthy black raspberry and blackberry stock. Eradicate infected wild blackberries and black raspberries near your raspberry patch. As the rust becomes systemic in the host, remove and destroy infected plants as soon as they appear in the spring. Thin healthy canes and keep weeds down to promote good air circulation which helps prevent spore germination and infection. There are no effective fungicides for control of orange rust at this time.
Under normal circumstances, I would suggest you take a sample to your local extension office. However, due to COVID-19, most offices are either closed or not currently taking samples. So your best bet might be to assume you have a case of blackberry orange rust, and follow the recommendations above.

I'm sorry for my confusion. If you have any other questions, please write again.