Hello Rita,

Thank you for reaching out to us here at the Colorado State University Extension Help Desk regarding your black raspberry cane issue.

The one photo you provided show very good detail, it's a great shot.  In order for us to accurately diagnose the issue and offer treatment options we need some further information and additional photos.

1.  When did you first notice this cane splitting and the growths?  How long has this been happening?

2. How much water do you give these plants and how frequently?  What type (sprinkler, hose-end sprayer, etc.)?

3.  Have your plants borne any fruit? If so, how did it look and taste?  

4.  Do you know specifically what cultivar of raspberry you have?

5.  What side of the plant is this condition present (North, South, East, West, or all sides)?

6.  What did the plant canes and leaves look like when you first noticed this issue?

7.  Have you seen any insects on the plants which you took note of?

Please send us additional photos of:

a. the leaves (both unaffected and affected).  

b. the branches/canes (both unaffected and affected).

b. the base or crown of the plant right at the ground level.

Rita, once we receive the additional pictures and your responses, we'll be much better informed as to what is affecting your raspberries.  Thanks in advance for your patience and assistance.  We look forward to hearing back from you.

Best Regards,

Carl R.

Colorado Master Gardener Apprentice

Hey there, Rita!

Thank you for all of that information and all of those pictures! That definitely helps us look into what might be happening. The good news is I have a few possibilities that might be causing your leaf issues! 

The first possibility is soil nutrient deficiencies. Our soil here in Colorado tends to be very alkaline and not very nutrient dense. Raspberries tend to thrive in more acidic soil which could be causing some of your symptoms. A lack in Phosphorus and Potassium may be the cause of leaf curling and wilting that you are seeing. Applying a fertilizer that has more Potassium and Phosphorus in the spring or throughout the summer should help with that issue! I will attach a PDF link that will help explain the symptoms with pictures of common nutrient deficiencies that you can look through! 

PDF LINK: https://ir.library.oregonstate.edu/downloads/8s45q9063#:~:text=Nutrients%20typically%20found%20to%20be,acid%20conditions%20that%20commonly%20occur.

Another possibility for the leaf issues could be spider mites. They are extremely tiny mites that you may not be able to see with just your eyes and may require a hand lens to see! They like to suck the nutrients out of the leaves which can cause a stippling yellow effect on the leaves and stems and may have some webbing present. They can also cause leaf curling. They have been very popular currently with the wind and warm weather we have been getting, and are definitely a pain to get rid of. The good news is they shouldn't cause any long term harm to your raspberries and should die off over winter. 

Now, for that first image with the canes themselves, we are still trying to figure out what that might be. A possibility is an insect called cane borer that can cause the wilting and discoloration of the individual leaflets. We aren't 100% sure on that but if you are in the area, you could bring us a sample that would really help us see what it might be! But otherwise it will take us some more time to see what might be going on there. If you are interested in bring in that sample, our office is located at 17 North Spruce Street, Colorado Springs, CO 80905. We are located on the 2nd floor on the far right side of the building and we have volunteers here from 9am-12pm and 1-4pm on Mondays and Wednesdays. 

Thank you again and we will continue to look into what might be happening! Good luck and we will be in touch again shortly,

Brooke A,

El Paso Apprentice Master Gardener