Leaves on raspberry & Canna Lillys turning black

Asked August 11, 2015, 2:20 PM EDT

The leaves on my newly transplanted raspberry plants and a canna lilly have suddenly turned black. The raspberry have been turning for about 3 days and the canna lilly just started. I have tried looking up on web sites what it is and what to do, but have found nothing. What do I do. I pulled one raspberry because it was totally black. All the plants have plenty of air.

Ramsey County Minnesota

5 Responses

This sounds like a fungal, or bacterial problem. We're seeing lots of these diseases lately, with all of the rain.

We would need to see some good close-up photos of the black leaves and of the canes in order to proceed. These plants are not related, so there may be more than one kind of disease going on.

I'll look for your reply.

Dear Mary, Almost overnight it spread to several other plants. I pulled leaves and stalks off the canna lilly because it was so bad this morning, so I have only the one photo and I hope you can get the idea from that. I have attached 2 photos from the raspberries. It has gone to the ground cover plants also. I imagine it is airborne in order to travel so fast. I also have a serious infestation of powdery mildew which I have been treating with baking soda/dishsoap/crisco oil (YouTube video), but it is not helping.This has been on my vegetables, starting with green beans and cucumbers. I am at the point where I am pulling things out and immediately putting them in disposable plastic yard bags.

Thanks for the photos of the basil and the canna but there aren't any of the raspberries.

Your basil has Basil Downy Mildew. This is a relatively new disease in Minnesota but it has become a world-wide problem with basil plants:

It's difficult to control, and as with many fungal diseases, spraying with a fungicide needs to begin before any symptoms are noted. Your home-made spray won't help, and it may cause some damage to your plants. You are doing the right thing by eliminating all plant debris. It should go in the trash - not compost.

Again, it appears that a variety of fungal diseases may be at play in your garden.

The raspberries are subject to a number of dieases. Lacking a photo to go by, take a look at this fact sheet and see if you can find symptoms that match what you are seeing on your raspberries:

I suspect the canna lily is showing signs of botrytis, or grey mold:

This has been a banner year for fungal diseases because of the wet, coolish nights. Unfortunately if you have missed the window of time that preemptive spraying for these diseases, your best bet is to make sure the plants are not watered overhead, all debris is picked up, and any leaves showing signs of disease are picked out and disposed of.

I know this is difficult to hear. I pulled my entire basil crop out in early August, 2012 because of the Basil downy mildew - just in order to have Something to harvest! Since then I have planted them in different areas, just to avoid any possible spores that may have overwintered in the soil.

Next year look for plants that are labeled resistant to these diseases. The cannas should be fine once you've cleaned them up and stored them away for the winter.

You may want to consider early spraying next year in order to thwart some of these diseases. Because you've got more than one fungal disease, make sure to check the label to make sure you're buying the right product.

Another good way to minimize fungal diseases is by applying a deep straw mulch around your seedlings (or s
tarts). The straw minimized splashing water that throws the spores around.

I hope this answers your questions. Please get back to us if you still have questions.

That is interesting that you say the two photos are of basil. I was given raspberry plants, most of which died immediately following the transplant. The photos I took were the supposedly raspberry plants. Thank you for all the information. I have just pulled three more Japanese beetles from my plants this morning - this time the geraniums. I feel as though I have been struck with several plagues this summer - never experienced this before. I pulled out the basil/raspberry plants. That's a "good one" if they are basil. Linda Andrean

How odd! You should be able to tell if they are basil or raspberries by the smell. Also, raspberries (even little ones) have tiny thorns or prickles along the stem.

Well...Better luck next year. Gardening is lots of fun/work/education and pleasure. Son't give up!