Blueberry leaves turning red, then dying from tip
I have a Blueray blueberry bush and I just noticed that all the leaves st the end of on one branch are turning red. The red seems to start on the inside of the leaf and expand toward the edges. When it gets to the tip of the leaf, the tip turns mottled brown and the leaf dries up from the tip back. I cut off the affected branch because I didn't want it to infect the rest of the bush. There is a little bit of red on other leaves on other branches, but not nearly to this extent. I'm attaching two photos. Can you tell me what might be the problem, and what I can do about it? Thank you.
Josephine County Oregon blueberries
Thank you for your question. I have a couple for you. Have you checked the pH of your soil? How much and what type of fertilizer are you giving your bushes? (One known cause of reddening of the leaves is excess nitrogen.) Finally, how much water have they gotten? (Another known cause is too little water, marginal leaf burn caused by drought.) Let me know, and I'll keep investigating. Thanks!
I haven't checked the pH recently but, when I planted them two and a half years ago, I dug holes about a foot deep and 3ft wide and filled them with a 4-1 mixture of Azalea mix and peat moss, so it should be very acid. Each planting hole has about 1.3 cubic ft of peat moss and 5.6 cubic feet of Azalea mix, and they're mulched with pine needles. I fertilize the plants with ammonium sulfate, which was recommended by Bernadine Strik when I took the OSU extension course on growing berries two years ago. She said that's the only fertilizer you need for blueberries.
I water the plants with micro-jet sprayers (two per plant). I water every other day, and try for about 1/4" in each watering session. (I use tuna cans to measure.) Unfortunately, this plant is getting a lot more water on one side than the other side this year. That's partially because the foliage is blocking the spray on one side and partially because of overspray from the plant next to it on the other side.This one has been getting 3/4"-1" on one side and only a trace of water on the other. I was hoping the excess water would get drawn over to the dry side, but maybe that's too much to hope.
The leaves that are turning red are on the side that's getting too much water. I looked it up and learned that red leaves can also be a sign of phytophthora root rot. The roots on the other side also might be suffering from drought stress, since they're not getting enough water. Does the side that the leaves are turning red on indicate which side is having root damage? Is there any way to tell from the look of the leaves whether they're turning red from drought stress or phytophthora root rot? If I bring in the branch with the red leaves to the Master Gardener's Clinic, would they be able to tell which it is (or if it's something else)?
It's really hard to change the micro-jet sprayer configuration at this time of year because the stakes are embedded in native soil just outside the planting holes, and the native soil is decomposed granite. I was able to dig out one of them this morning and move it closer to the other side of the plant, but I don't know how much that will help. I really appreciate any advice you can give me!
Thanks for the additional info! If you've been trained by Prof. Strik, you've had the best! I'll keep researching tomorrow, and get back to you. Perhaps we can enlist Prof. Strik and/or the local Extension office to help solve the mystery!
That would be great if you could get Professor Strik to help! I'll bring the branch into the Master Gardeners' Clinic on Monday. I cut it off the bush on Friday because I was concerned that it might be diseased, and I put the stem in a jar of water. I hope it's still fresh enough tomorrow for them to be able to do whatever they do to determine what the problem is. Thank you for your help with this.
Hello! Happy to try to help.
First of all the symptoms do look like some kind of stress -- not nutritional I think. I do think that one side of the bush is getting too much water and the other possible too little (assuming as you indicate that one side is getting 3/4 to 1 inch of water every other day -- unless I misunderstood). When you can (in winter?) adjust the micro sprinklers to make water application more uniform. You can check soil moisture after watering by using a soil sampling core or a towel and doing a little digging. After irrigation the root zone area (drip line of bush down to about 12 inches deep) should be relatively uniformly saturated). Then before you irrigate again the soil moisture should be about 30% of what it was when saturated. These plants don't like to be in saturated soil all the time; as you mention, this can aggravate or lead to root rot.
Are the symptoms spreading to other leaves on the same cane? If so, if may be a disease. Look for any cankers on the stems (https://pnwhandbooks.org/plantdisease/host-disease/blueberry-vaccinium-corymbosum-fusicoccum-canker-...).
If symptoms are not spreading, it could simply be related to heat stress. We have had a relatively cool spring followed by very hot weather. This has led to some leaf bronzing and burning and even some berry shriveling due to heat issues. Nothing to do about that.
I'd suggest watching symptoms carefully and if they progress, take a sample to the OSU Master Gardeners for help in diagnosis.
Thank you very much!
I was thinking of replacing the micro-jet sprayers with drip emitters or bubblers to water more evenly, but I'm concerned that they'll only wet the surface in spots and I don't want the peat moss to dry out.
Bubblers would spread the water over a wider area, but you can't control how many gallons per hour they're putting out. Also, I might have the same problem with bubblers as with sprayers, that they get blocked by low hanging foliage. The Legacy and Blueray bushes both have weeping habits, so it's hard to keep the foliage (and berries) up off the ground.
Drippers come in 1/2 GPH, 1 GPH, and 2 GPH. Which size would you recommend for soil that has a lot of peat moss in it, and how many drippers per plant? Or would you recommend bubblers instead?
Thank you very much for your help!
I would suggest drippers. Check to make sure peat moss isn't getting too dry to assess frequency of watering. Rate of emitter doesn't matter too much (smaller gallonage means leave on longer), but I would suggest 1 gph as that's a good compromise with not likely clogging (water quality) and not applying so much at once that water all goes straight down.
Thank you! What's a good number of drippers per blueberry plant?
If I make a ring around the plant about a foot from the edges of the crown, that would require about 4 feet of 1/2" drip line. I could put in four drippers about a foot apart, or six drippers about 8" apart. What would you recommend?
And is that the right distance from the crown? I want to be sure the drippers are close enough together to get even coverage over the whole planting hole, which is 40" in diameter..
Thanks so much!
About a foot from the crown edge is just fine and 4 per plant works well, either with two lines (one per side) down row or a circle as you describe.
Thank you. And thank you for the link to the article on Fusicoccum Canker. My Blueray plant is definitely infected. I'm attaching three photos. (The white spots in the photos are Garden Dust to control caterpillars.)
The first photo is a cane that looks just like the ones in the article. There's another cane in the background on the far right of this photo that is also definitely infected. I'm not sure about the canes in the other two photos. The one in the second photos has a red area around a cicada scar, and more reddish stippling all along the cane, but it doesn't have the obvious lesions the canes in the first photo have. The one in the third photo is a junction where two small branches come out of a cane, and it's red around the junction. Can you tell from these photos if the second and third canes are also infected?
There are also some smaller red spots on other canes. Are all red spots early indications of infection? Should all canes with red spots anywhere on them be pruned?
I assume that I should prune the affected canes immediately. I know you're generally not supposed to prune in summer, and this will be a significant amount of pruning on this bush, but I don't want to risk it spreading to my other plants.
I've used Serenade spray for the past two years on this plant because it had a couple of stem cankers in the year I planted it (2015). I don't know if the Serenade is effective since, obviously, the plant is still infected. Will Serenade be effective at this time of year for protecting other canes after removing the affected canes?
Should I remove this plant entirely, since it has had a history of stem canker infection? If I remove it, is it OK to plant another blueberry bush in the same place (I have limited space available), or would the soil be contaminated now?
Thank you very much for your help.
The only way to know if your plants have this disease is to submit a sample to the OSU Plant Clinic. The OSU MGs in your local Extension Office can help you with doing this. Please refer to control methods for this disease IF this is what your plants have at: https://pnwhandbooks.org/plantdisease/host-disease/blueberry-vaccinium-corymbosum-fusicoccum-canker-...
Thank you. I'll bring in samples this morning to my local OSU Extension Master Gardeners' clinic.
Thank you very much for your help!