Found this on the web, maybe it will help you.

Is Something Bugging You?

Here are some clues, my dear Watson  tiny holes in the leaves; a whole side of a lily pad mysteriously disappears; thereÂs something nasty stuck to the bottom side of the leaf. Oh, no  could it be that your plants are being bugged? ThatÂs exactly whatÂs happening. The culprit could be one of many from the Pond Pest Most Wanted List. From Aphids to Japanese Beetles to Leafhoppers to the Great Pond Snail himself  if caught early enough the plant can be saved! First of all, remove any leaves affected. If that doesnÂt do the trick or in severe infestations you should isolate the plant and treat it.

If you have fish you simply cannot treat an infected plant in the pond. How do you treat them without harming the fish? Elementary, my dear Watson. You remove them to a plant hospital. Plant hospitals come in lots of forms. You can use the kids wading pool if theyÂll let you Âor a couple of large thick-walled plastic storage containers. Fill them up with water and place the plants like you would place them in the pond. Sprinkle the tops of the plants with an insecticide such as seven dust taking precautions not to dust the pond accidentally. After a week or so the plants can be rinsed off and returned to the pond.

Most probable cause is aphids or caterpillars, most likely it is aphids. If you have no fish, spray some aphid repelant on the top of the leaves, you can get it at lowes or home depot in the garden center, it will keep whatever bug id doing it away, even if it is not aphids. Re-apply every 2-3 weeks.....Amanda

Could be aphids but you can see them pretty easy. There will be tons of very tiny darks spots all over the pads and the best thing to do is spray them off with a hose so they drown.

The other thing it could be is very, very tiny clear worms on the backs of the pads. They are really difficult to see. Best way to see them is to use a magnifying glass or go outside at night with a flashlight and look at the back of the pads. You'll see them squiggling all over the back of the pads.
I've always defeated them by keeping old pads picked off and simply washing the backs of the lily pads with the hose and my hands.

Thanks everyone,
I like the spraying with water treatment. Easy and very organic! thanks for your help.

Aphids are really easy to see and there are usually lots of yellowing pads too. They really stand out on the yellow pads.

Any chance a native turtle has wandered in?

No, haven't seen any turtles in the pond. I have seen some aphids on the lily blossoms, so maybe its that. I'll spray them off tomorrow. Thanks.

I went out this morning and turned the leaves over, and there were a fair number of snails on them. Could they be doing this?
If so, any way to get rid of snails without using a chemical??

P.S. Do certain fish eat snails? Minnows?
Shouldn't my frogs be eating them?

Catherine, I've read that you can trap some snails by attaching cabbage or cucumber to a string and putting it in the water. Just pull it up and destroy what shows up.

Brenda

Snails can be the problem. Frogs won't eat them. They don't move fast enough to trigger their prey drives. They are rather difficult to get rid of. I've been trying for years to get rid of them in my aquarium and ponds. They come in on plants purchased and traded.

Just a stray memory flitting through my mind at reading this thread: Although I was too squeamish to do so, my mother used to control snails in an aquarium by sticking her finger in and squishing them against the sides. The fish would fall all over each other getting to them to eat them.

Anne

Thanks everyone. I think I'll try the cabbage-on-a-string thing. You wouldn't be foolin with me would ya Brenda......just to make me look silly? :)

Catherine,

I guess the "catch a snail with a cucumber on a string thing" is sort of like crabbing but at a much slower pace. hahahaha

Anne

I also squish them against the sides in my aquarium, I use a the algae scraper not my fingers but they still breed faster than I can squish.

Well, the cabbage is out there a-danglin'. We'll see. Hope it doesn't attract coons, which then plunder the whole watergardens.
Sorry, I'm not a squisher.

LOL!! I promise I'm not foolin' with you, Catherine! Besides, what could I possibly get out of it without a picture of you next to the pond, looking forlorn while holding a stringful of soggy cabbage? :D

Brenda

LOL Brenda! Who knows......maybe you're a soggy cabbage sadist. hahaha
I noticed I have alot of holes in my heuchera plant too. I thought frogs and toads were supposed to take care of those things??

I feel your pain, Catherine. We have a major overload of earwigs this year, and they're loving the seedlings I've been trying to start....as well as more established plants. They're GREAT aphid killers, but they are so naughty when not eating those. Cat food cans full of veggie oil (or even better, fish oil) and beer go a LONG way to nabbing the slugs/snails and earwigs.

Oh, and I have tons of frogs this year, too. Get to work, kiddies! :D

Brenda

I pulled on my chest waders and went into the pond to clean off my lilypads and blossoms. Tons of aphids! Who knew the little guys could swim...shortly after washing them off, they swam, or floated right back on! I pulled out the damaged or dead leaves, and will spray them with the hose a couple of times a day. My mosquito fish will eat them, but they can't keep up. My big fish ignore the bugs.

By the way , the reason I use waders is because I have "Backswimmers" living in my pond. Those are bad bugs; they have a bite like a yellowjacket. Imagine an amphibian attack group that checks out everything entering the pond. Scary, and the only way to get rid of them is scim them up and smash them.