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Beginner Gardening Questions: Leaves curling, closing on my hydrangea arborescens

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teainthegarden
Quebec
Canada

June 3, 2013
2:19 PM

Post #9544913

These hydrangeas are growing in a shady spot, that gets increasingly more shady. I did some pruning a few weeks back but I thought my pruner was clean.
Anybody have an idea what's wrong?
Thanks!

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luis_pr
Hurst, TX
(Zone 7b)

June 3, 2013
4:54 PM

Post #9545106

Below are some possibilities to check. My guess would be to check for pests first. Leaf curling can be caused by any of the following:

* by pests: Aphids like tender new growth; you can release lady beetles and beneficial insects to fight off pests. The hydrangea leaf curler caterpillar/moth (and similar pests) hides inside the curled leaves to protect itself from pesticides. If the caterpillar is behind this, you should see it inside (yes, you would have to unfurl the leaf). If you find nothing inside, check for aphids. I suspect the caterpillar because one of the pictures showed something had eaten part of the leaf.
* by cold weather (late frosts);
* as a reaction to fungicides/insecticides applied nearby;
* by some weed preventers; they can cause curling but the concentration has to be large.
* Lastly, check for potassium deficiency using a soil test kit that checks for low levels of potassium, nitrogen and phosphorus.

See below for hydrangea leaf moth damage:
http://bygl.osu.edu/bimages/2010/05/cimage2010_05n2505_w720.jpg
For information about this pest, read:
http://hg.ohio.com/2011/05/bygl-may-26-2011/

The caterpillar causes aesthethic damage only; I have never heard of it killing a plant. You can control them using Bt (Bacillus thuringiensis ) or by killing the caterpillar manually. They are kind of gross so there is a little Eeeck Factor with that last suggestion/procedure. Sorry. If you decide to apply Bt, remember to reapply it next year at around the time when this problem started (say, early to mid May if that is when you noticed the problem).

Aphids are very tiny pests that can be found by looking for excrement in the form of honeydew. They can be dislodged with a sharp water spray from a hose. Or you can release ladybuds. Or you can use horticultural oils and insecticidal soaps.

Does that help you?
Luis


This message was edited Jun 3, 2013 5:59 PM
Diana_K
Contra Costa County, CA
(Zone 9b)

June 3, 2013
8:55 PM

Post #9545429

Ditto luis-
Looks like a bug that curls the leaf. You may find some webbing in the folded or rolled leaves, and something inside.

Other than that, there are some fungi that make leaves look like this on some plants, but I am not sure if Hydrangea gets those fungi.
teainthegarden
Quebec
Canada

July 29, 2013
8:22 PM

Post #9615957

Thanks!!
WeeNel
Ayrshire Scotland
United Kingdom

July 30, 2013
3:02 AM

Post #9616103

If possible, remove the affected leaves and burn them, or uncurl and see IF there is a bug inside the curled leaf, like the others have stated, there are many reasons for this to have happened, on the other hand, it might be shock after a good pruning, whatever it is, I hope you can resolve it soon as you have got nice plants and look healthy aside from the new problems you have gained.
Good luck. WeeNel.
teainthegarden
Quebec
Canada

June 26, 2014
10:19 AM

Post #9878162

Just wanted to come back to say thanks and note for other who may have a similar situation -- you all were correct in your diagnosis: caterpillar/worms inside.
Thanks for the help!
WeeNel
Ayrshire Scotland
United Kingdom

June 26, 2014
3:00 PM

Post #9878368

The Caterpillar is the grub from the leaf curl Moths, they lay there eggs on the leaf, then spin a fine Gossamer silk like blanket to wrap around the eggs attaching them to the leaf as they do so, the silky material curls the leaf and it is a great way of hiding the eggs from birds and other predators till the eggs hatch out into the caterpillars, they eat the leaf and after a while, they become the adult moths and the cycle goes on for another year.
These Moths don't just lay their eggs anywhere, they are more prevalent on plants like the Lilac, they might be directly next door to say a Hydrangea and NOT be interested in using that as a host plant, leaf texture has a lot to do with their choice as plants like Hydrangea have a thick vein on the leaf making it more difficult to fold into the curl needed to hide the Moth's eggs.

I don't know of any substances that would kill off the eggs while still held within the curled leaf BUT the time to remove the problems is as soon as you see the curled leaves, by removing the leaves, crush, burn or shred the leaves kills the eggs, the plant has time to make new leaf and removing the leaf and destroying the bugs, you prevent the cycle of the re-infestation.

Hope this helps you a little and you see a recovery of the plant, remember by pruning the plants, your also removing the flower buds.
Kindest Regards.
WeeNel.
teainthegarden
Quebec
Canada

June 27, 2014
12:12 PM

Post #9879177

Thanks for the info! There are no lilacs nearby, though, just ferns and weeds. And I think I moved the caterpillars with the plant a couple years ago and last year because some hydrangeas that I moved to different areas have the same thing (but none near lilacs).
Thanks!

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