I am guessing SE BC means southeast British Columbia? Cercospora and leaf chlorosis have nothing in common really - one has to do with water/humidity and the other is a reflection of a nutrient imbalance.

Do some research on the cercospora - it tends to be very seasonal and more common to nursery-grown plants than to those established in the landscape. IOW, nursery-grown plants that have it tend to outgrow it once they are planted and established in the garden. You could prune it back but I don't believe that's really necessary. Just clean up really well after the leaves fall a good mulch will help as well. And if you can avoid overhead watering (and help from Mother Nature), chances are very good you will not have anywhere near the problem next season.

The chlorosis I'd suspect is due to iron deficiencies. Iron (and certain other nutrients) becomes bound up or inaccessible in soils that are not adequately acidic. You can work now to increase soil acidity (sulfur applications) or use an acid lover fertilizer in spring. These generally contain acidifiers to increase or keep soils acidic. Now is not the time to fertilize, however, specially in your zone.

Gardengal thanks for the response. I guess I am under the wrong impression. From all the research I have done cerospora damages the leaves ability to function properly. Thus the plant robs nutrients from healthy leaves to try and 'fight' the problem. So the whole plant, especially the leaves with cerospora, show signs of chlorosis.

I guess I was also not specific enough. My soil PH at this plant tested 6" down is 6.4. Sulphur and Aluminum Sulphate have been added, as required, to keep it at this level as well to turn the blooms blue from aluminum.

I agree it is seasonal, I have never had this problem this late, as stated above, as we are generally very dry here.

I did go out and prune tonight. Upon close inspection I would guess over 15% of leaves showed 25-50% damage. I also changed the mulch again as we are being forecasted another batch of thunderstorms.

I do appreciate your insight..Thanks again

SCG

You could still get iron chlorosis at the end of the season in other ways.In late August and September, my summer weather changes. The 100-degree temperatures and dry weather is replaced by cooler temperatures that often trigger thunderstorms, which can dump a lot of rain. When the storms do dump a lot of rain, the roots can get waterlogged and, in my case, this causes episodes of iron chlorosis.

I would also do a soil test to check for mineral defficiencies... like too little magnesium. It has similar symptoms and affects older leaves in plants first.

Thanks for the info luis.

I am wrong in assuming the chlorosis is caused by cerospora? This is the only one out of 5 that is showing any chlorosis and the only one to get both magnesium sulphate and chelated iron back when I thought the cerospora was gone.

My soil is sandy hard pan which is extremely fast draining.

Picture shows a leaf from another ES on top of the one in question. You won't see much cerospora as I removed all the badly infected leafs last night to stop spore transfer in the upcoming (if it comes) thunderstorms.

Thanks again.

This post was edited by SouthCountryGuy on Wed, Aug 14, 13 at 14:34

Can you post a photo that illustrates your concerns? Advanced cercospora can certainly result in yellowing foliage (many fungal diseases will do so) but that is quite a bit different from chlorosis, which is a lack of chlorophyll. As Luis notes, root issues are common causes of chlorosis as are various nutrient deficiencies. This problem is not usually associated with any pathogens (although discoloration/yellowing can be).

Whatever the cause, at this late in the season, I'm not sure I'd be overly concerned. Cercospora tends to be more cosmetic than a serious disease issue with home landscape hydrangeas and by all accounts you have dealt with soil pH and nutrient levels adequately. You can't help Mother Nature - if rains are much more plentiful this season, that's bound to produce some side effects. Just keep garden sanitation at a high level and keep your fingers crossed that next season's weather is more typical. Chances are very good this situation will not repeat itself.

I've attached an excellent informational link about this disease. You will notice that there is no mention of chlorosis developing as a result of this disease although yellowing (a different condition although appearance is similar) can happen.

Here is a link that might be useful: cercospora info sheet

Thanks, gardengal48. I mistakenly was calling the leaves yellowing chlorosis as I thought it fell under the definition. My bad and I can see the confusion now.

I have dealt with cercospora in the spring before but always had it dealt with by now. That was the basis of my concern.

My pruning was probably not warranted I just wanted to try and eliminate spore transport. The cerco has only really gotten bad in the past few weeks which have been very dry with only the occasional thunder shower.

Thanks for the link, I have not seen that page.

I edited the above post as I forgot to include the pic.

Thanks again I feel better knowing the leaf yellowing is not of major concern.

SCG