shibashinu
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Joined: Sat May 11, 2013 2:21 am

Mysterious illness??

Hello c: I'm new here but I really need help figuring out what's wrong with my hydrangea.
I think it's an amethyst mop head (hydrangea macrophylla) but I'm not quite sure since I bought it without a label at a school fair.

It was seemingly healthy when I first got it but recently it's been developing crinkled but green leaves towards the apical meristem (3rd picture) and yellowish spots on some other leaves (2nd picture). Can someone help me diagnose this problem? I've checked for aphids or other bugs but I found nothing. I'm currently growing it in a pot but I hope to move it to a larger pot later.

Also, it might be important to tell you that I've recently been treating it (about 1day) with a 1:9 milk/water solution for what I believe is powdery mildew. I noticed the fuzz early so hopefully it won't spread too far.

Thank you!
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Location: Amherst, MA USDA Zone 5a

Re: Mysterious illness??

Might want to review this for sharing photos:

https://www.dropbox.com/help/167/en

Or just upload them to our site directly. ;)

luis_pr
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Location: Hurst, TX USA Zone 7b/8a

Re: Mysterious illness??

It sounds like the start of powdery mildew but the pictures would greatly assist. In the landscape, warm days, cool nights, and light rainfall in the spring favor disease outbreaks and I have read of such problems here and there already. PM can start by noticing some small round areas that turn yellow, white or grayish. White, cottony hyphae of the powdery mildew fungus becomes more obvious and starts to cover larger areas of the leaves. Lastly, the leaves get real ugly, turning purple ish.

"Good housekeeping practices" might help you at first: separate plants to improve air circulation; water the soil (and not the leaves) and water early in the mornings (as in just before the sun comes out). Remove any fallen leaves and other plant debris. If the outbreak is already advanced, consider replacing the mulch with new mulch; mulch, leaves, stems/branches are good places for the spores to hide. When the plant goes dormant again in the Fall, dispose of the leaves and of all the blooms in the trash; do not use the compost pile as this will help spread the spores. Observe if the mulch stays moist or if the growing area is humid; those are indications that you could be watering too much and helping the spores develop. Depending on how big of a problem you have, it may take several season to control the spread.

A solution of milk and water can also be used. I have successfully tried that with some Crape Myrtles that are planted near humid areas that I cannot control (near pools and a creek). If the problem gets worse and you do not mind using fungicides, consider spraying as soon as you see signs in the lower part of the leaves (I would start spraying on the same months for 3 years). Get the upper and lower leaf surfaces wet with fungicide. Here is a list I have of fungicides for the control of powdery mildew on hydrangeas (I am listing the active control ingredient and the commercial name in parenthesis): azoxystrobin (Heritage; has the smallest application rate and largest repeat interval); fenarimol (Rubigan; Cleary's 3336) or triadimefon (Bayleton). You can also use Sunspray Ultrafine Oil. As they usually suggest when talking about fungicides... it is best to make one application of one type of fungicide and then use a different fungicide (fiddrent active ingredient) on the second application; and so forth.

Luis

PS - If you have difficulty with the photos, just copy/paste the URLs in a reply. Make sure the service you use to store the pictures into allows for "public" access.

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