The white stuff looks like bird poop. Did you actually take any leaves into the garden center or just describe it? I cannot believe they would think that was insect eggs if they saw it - it's poop, plain and simple! And just pick off the caterpillar and destroy it. All manner of bugs appear that will eat plant leaves.....it is just a fact of nature and nothing to get overly concerned about. Plants have been dealing with these sorts of issues for eons and live and will actually thrive with a few chewed leaves.

I would check to see if there were more and just pick those off as well. Whether you would need to look into any more serious treatment would depend on the numbers but I doubt you have anything to worry about. Chill :-))

I agree with bird poop, squish the caterpillar, and don't worry about the holes in leaves. Annabelle is a plant you could run over with a truck and it will come back. I've never had leaf diseases, though I have the caterpillars that bind the leaves together in early spring that I squish. Even if it were disease, it most likely wouldn't spread to other plants beyond related hydrangeas since most foliar diseases are specific to certain plants. Even powdery mildew, which occurs in many plants, is different organisms causing it for different types of plants. So no worries.

Over the 15 years or so I've had Annabelle, I have

- had mice and voles eat the bark off every branch in the winter

- had 4 feet of snow come barreling off the roof and break every branch

- rudely dug up rooted branches or even just pieces of large roots, plopped them in a plastic-bag-lined cardboard box with some soil, and given them away to other gardeners to plant.

Regardless they grow and bloom without missing a beat, though if winter damage is too severe, I do prune off the damaged branches to the ground. I think the only thing that can damage Annabelle hydrangea is too little water and too much sun together.

Thank you for the comments! I didn't take a picture in, simply described it--but I'm sure it could be bird poop now that it's mentioned.

ill try not to worry too much about it and see if it improves.

thabks!