Hydrangea Leaf Pest

(Question)

I think my plant is the Annabelle variety and is in my backyard in central Toronto. It has had leaf curl the past couple of years, so I removed what evidence I’ve found. Now something else is preying on the leaves -photo attached.
Thanks for your help.

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(Answer)

Hello:  Thank you  for contacting us with your inquiry. Without a photo or description of the insect it is extremely difficult to determine exactly what is eating your hydrangeas.  Hydrangeas are seldom bothered by pests but your plants look like they might have more than one pest bothering them. I don’t believe the yellow spots are related to the  hole.  In the past you have had larvae that caused leaf curl;  now you look like you may have a different larvae or a small beetle that is simply eating the leaves causing large irregular holes.  Do you see any little green worms  or light tan beetles on the underside of the leaves?  If so, a commercial insecticidal soap, available at your local garden center might be in order, or hand picking them off (but that is difficult if you have a large number of large leaves).

You also might  have aphids (or some other sucking insect) which are  causing the yellow spots. Aphids might be collecting along the stems and backs of the leaves.   I didn’t see any aphids  in the photo but have a look.  Again a safe commecial spray (the same one used for the larvae) would help.  Strong blasts of water  are said to also help to knock off the aphids from the plant however, you have to do this often. If your plant is in fact infected by aphids you will notice a shiny sticky substance on the underside of the leaves along with ants on the leaf surface. This sticky substance is honydew that is excreted by the aphids and which attracks the ants.

The leaf also appear to be chlorotic, pale green.  Usually this means that the plant is not able to absorb iron and other trace minerals from the soil.  Often high pH (i.e. basic soil) prevents these nutrients from being absorbed by the plant.   I wonder if it is time to ammend  your soil ?  To accomplish this, add a layer of really good triple mix.  Two or three inches of organic mater including clumpy aged manure, might help strengthen the immune system of your hydrangeas, change the environment for the bugs, and help prevent reoccurrence of pest problems. No need to dig it in.   Another idea  is to remove some  older plants to allow more air circulation as well as allowing the  uptake of   more available nutrients per plant.

This website might be of interest:

 

Hydrangea, climbing and bush