Deformed leaves on rhododendron?

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CatMint20906 Silver Spring, MD(Zone 7a) Nov 16, 2013

My rhododendron is putting out some odd-looking leaves and buds. First is how it looks normally, and then is an example of one of the deformed leaves. Anyone have any idea what would cause this?

Thumbnail by CatMint20906 Thumbnail by CatMint20906
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Diana_K Contra Costa County, CA(Zone 9b) Nov 16, 2013

Gnarled and burnt leaves like that suggest some damage, perhaps while the leaves were in the bud or barely starting to open. As they continued to open they could not because the damaged tissue could not expand as the undamaged tissue did.

There are several things that can do this.

1) Pest damage. Some insects specialize in sucking the juice out of buds and youngest leaves. While the piercing mouth parts are small, they can do significant damage to the leaf tissue at that time.

2) Nutrient deficiency. Calcium deficiency and Boron deficiency or excess are 2 that can make the new leaves distorted. Some nutrients in excess can interfere with the uptake of another, leaving the plant deficient in the one that is blocked, even if it is in reasonable supply in the soil. The wrong pH in the soil can interfere with nutrient uptake, but unless something happened suddenly (like a new concrete pour nearby) pH problems do not show up as suddenly as this seems to have shown up.

3) Herbicide or other pesticide damage.

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CatMint20906 Silver Spring, MD(Zone 7a) Nov 16, 2013

thanks, Diana. That is very helpful.

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plantfreak78 Rolesville, NC(Zone 7b) Nov 16, 2013

Check into Rhododendron Gall Midge. The damage looks very similar to that.

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CatMint20906 Silver Spring, MD(Zone 7a) Nov 16, 2013

thanks, Plantfreak.

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CatMint20906 Silver Spring, MD(Zone 7a) Nov 16, 2013

I went out and checked and it does seem similar! I wonder if I should use a a systemic and if so should I wait till spring?

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plantfreak78 Rolesville, NC(Zone 7b) Nov 16, 2013

I work at a nursery and we see it every spring. By this time of year the damage is already done so all you can do is cut off the affected parts and dispose of them (just in case they're harboring eggs). Then treat next year's new growth with a systemic to prevent it from happening again.

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CatMint20906 Silver Spring, MD(Zone 7a) Nov 16, 2013

thanks, Plantfreak! I appreciate your advice.

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