Brandond,

I am in central Florida with 140+ blueberry bushes in full sun and we have months of 95+ days and the bushes don't bat an eye. Are you sure it is the heat that is doing it?

What are you fertilizing with and how much? You are sure the bushes are not getting dry? If you have a mulch reach down and under it to make sure you are not just soaking the mulch?

When you say killing the stem....do all the leaves on a limb turn brown and if so do they stay on the bush and not fall off? If so it could be blight?

Brandond, Yes I have a similar condition with my 2 yr. old blueberry plants. I've done considerable research on the internet and came to the conclusion its either bacterial or a fungal or both, I just don,t know. Very disapointing. I questioned the oval elongated dark spots on the stems last year, here on GW. The plants that I have the problems with, came from a very well known, reputable plant supplier and I just couldn't believe that they would have a promlem with their plants. I,m interested on the replies you will get. luke

IM not sure of anything other than im losing to many bushes. Some bushes get a tan/maroon color on the stems and the leaves start burning from the outside in. I would hope that it is something other than the heat, in fact I went ahead and sprayed with a fungicide since I wasnt sure. I would feel better about it if it was a fugus rather than heat since our summers have been running on the hotter side the last few years. I would also say that the bushes that were a bit iron cholorotic have done worse that the lush colored bushes. Still this has been a sudden dismantling of my overall numbers. I have fertilized as soon as 2 weeks ago with iron sulfate. Could fertilizer burn the bushes this way? I used iron sulfate and amonium sulfate.

How much ammonium sulfate did you use? What mixing ratio? Do you use a fertilizer injector?

Ammonium sulfate could certainly cause your problems.

Sounds like fertilizer burn to me.

Luke, the elongated maroon ovals are a type of canker disease. One of the first blueberry plants I bought was a Premire Rabbiteye from Home Depot. It had alot of the dark oval blotches on its steams but I didnt know better at the time. It died with in a year. I should have cut the plant back to the soil but didnt. Oh well, that was a lesson learned.

Without knowing all the conditions and care being provided, it could be any number of things causing problems. Is there a specific web site or person that you are getting tips or direction from?

Blueberries don't need to be fertilized constantly, even in pots. Two highly regarded sources say to fertilize blueberries in spring/late spring:
DWN Grow Your Own Blueberries
CARE OF SOUTHERN HIGHBUSH BLUEBERRIES

Note: There are no summer fertilization directions at either location

Make sure you are giving them ample water. Blueberries are thirsty, requiring more water than most plants. A short dry spell can set them back, while even moisture works really well.

Here is a link that might be useful: The Perils of Sulfate of Ammonia: It does more harm than good

I apply one tablespoon of Schultz's Plant Food-acidic formula, dissolved in 4 gallons of cold tap water, to each of our blueberry shrubs. There are two applications, one in late March, and the second in April. The latest I have ever applied fertilizer is mid-May. That is all the feeding our blueberry shrubs get, however I do water, and apply agricultural sulfur as needed, to lower soil pH. I have also used Miracle-Gro on our blueberry shrubs, using the same method outlined above. Our shrubs are generally healthy, although I do see a little rust now & then, which is pruned away.

Southern rabbiteye blueberries are a different plant than highbush blueberries (corymbosum sp?)

The former are not going to be damaged by heat like the highbush. My highbush couldn't stand heat like that either. Mine suffered terribly when we would get dry heat 95 + degrees. They are from New England where 100 degree dry heat days never occur. I plant mine here in part sun. Full sun is for other plants who demand/prefer it.
John S
PDX OR