i had the same problem! Til my son brought home 3 leopard frogs and put them in the pond. 2 weeks later no spots! I would suspect they are bugs, what kind I don't know but those frogs cleared them up!

i had the same problem! Til my son brought home 3 leopard frogs and put them in the pond. 2 weeks later no spots! I would suspect they are bugs, what kind I don't know but those frogs cleared them up!

i had the same problem! Til my son brought home 3 leopard frogs and put them in the pond. 2 weeks later no spots! I would suspect they are bugs, what kind I don't know but those frogs cleared them up!

i had the same problem! Til my son brought home 3 leopard frogs and put them in the pond. 2 weeks later no spots! I would suspect they are bugs, what kind I don't know but those frogs cleared them up!

Have you looked closely at the little black spots? It sounds like aphids. If aphids are the problem: A light coating of Pam cooking spray will suffocate the aphids. It's completely harmless to your other pond critters. Spray the waterlilies late in the day (when there's no chance for the sun to burn them) - let it sit 15 min or so and then rinse off with your garden hose.
There will be a bit of an oil slick, but your skimmer will take care of it in a few minutes. It'll dissipate soon enough even if you don't have a skimmer.

One treatment lasts a while: I usually have to do this 2 or 3 times per season, but haven't seen any aphids this year. Good Luck.

Thanks for the advice. They will be getting a dose of Pam tomorrow night when I get home from work!

One question... Do I need to be concerned about aphids on duckweed? What about on the roots of the plants?

Not much you can do about the aphids on duckweed. They won't be on the roots under the water.

I am afraid I have to disagree about the problem and solution. It sounds more like a fungus called Black Spot. The Pam would work if the problem is really aphids but won't do anything for a fungus. Black Spot and Brown Spot are common problems with pond plants. Usually the removal of affected leaves is the easiest cure along with increase of oxygen in the water (a pint of Hydrogen Peroxide to 1000 gallons of water or increasing water turbulance) and fertilizing the plants that show yellowing. Increasing air movement is also useful. Check the plants for Crown rot and discard any that are affected. Sandy

There could be another culprit. Take one of the affected lily pads and turn it over and look at it very closely. You need to look for very, very tiny clear worms that will be squirming like crazy. They are very hard to see and you may need a magnifying glass to see them. Also, its easier to seem them at night with a flashlight. These little worms can do a real number on plants. Whenever I had them I would just keep trimming off all the bad pads and washing off the remaining ones. I did this every day until the infestation was gone. I also threw away most of the floating plants and treated the remaining ones outside of the pond, then returned them after a few days.
Also, if you've had a weather change like we have had in the last week, you will usually see some changes in your plants. My water plants will be winding down here in a few weeks. They've yellowed slightly this week and growth and blooming has slowed with the slight cool down in temps.

Now I have even more questions.
1) If there are aphids on the duckweed, and if I don't kill them, won't they just spread to other plants?

2) Can I tell if there are aphids by feeling the leaves?

3) Part of Sandy's advice was more oxygen. Given the nature of my water feature, more oxygen is one thing that I am pretty confident that it doesn't need. Overall it is about 65 feet long and has a vertical drop of about 8 ft, including two waterfalls. I haven't fertilized the water lilies in about a month. However, over the weekend the string algae grew like crazy. Doesn't that indicate that there are plenty of nutrients in the water?

4) Lefd05 mentioned a weather change. I'm in Boulder, CO. The weather has cooled off a bit. Now it is in the mid-80s to low-90s. Also, we have finally started to get some rain. I haven't checked the water temperature in a few days, however, I doubt that it has dropped more than a couple of degrees.

5) I introduced the water hyacinths 3 weeks ago. I bought them at a large, local nursery. I am suspect that they may have brought this problem with them. Sound reasonable?

It sounds like I have some homework assignments. At lunchtime, I am going to look at the duckweed in the pond where I got mine originally. I want to see if its color is different from what is in my pond, or perhaps I am just imagining things.

I will try to take and post photos tonight.

I need to carefully inspect some of the diseased leaves.

Anything else?

OK, tonight I checked the surface of one of the lily pad leaves. I ran my finger across it and got lots of little black things, which seemed like they could be aphids. In addition, the water skimmers were all around, and on, the lily pads. I took the advice of nmpondguy and sprayed the leaves of sick plants with Pam. In addition, I checked the water temp - 74 degrees - down about 7 - 8 degrees.

Below are pictures of the water feature and the sick plants. The first picture is the upper part of system. The second is the lower part. It's in the lower part that the problems have been concentrated. It's hard to get a sense of scale, but the large pond is about 10' x 20' and the whole thing is about 65' long.

Thanks to everyone for the advice.

Rick

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You have been busy! The leaves in the last picture with the soggy black edges and yellow interiors have aged out. Remove them without a qualm. There is algae because there is so much sunlight allowing photosynthesis. I suggest more plants for shade other than water lilies which need calm water to thrive. It doesn't need to be water plants. Pond side plants would be fine although the water plants would eliminate the algae faster. It does appear the spots are from insects. I am surprised you would have that problem in Boulder. Do you have a test kit? Sandy

Yup - Aphids. I'd guess you've treated them by now. Winged Aphids can fly to your pond and then begin laying the wingless ones you see in abundance, so they may or may not have come in on new plants.

Like sleeplessinftwayne said, the yellow pads appear to just be old and ready for pruning. I remove old pads, stems and spent blooms nearly every week.

BTW: You did a masterful job building that water feature. It's a beauty to behold!!!

Here is a link that might be useful: The Aphid Life Cycle

Boulder.....I'm here in CO too, on the western slope. Sounds like weather is about the same for us. We are on the downhill side of summer now. Your lilies don't look that bad. You do have aphids but the yellow and rotting pads are just old and need taken off the plant. You will see your lilies start to slow down in just a few weeks. They will stop blooming early September and stay green until frost time.
Your pond looks wonderful! You've done alot of work there.:)

Your pond and view are amazing.

Those are most definitely aphids!

Remove all the yellow pads.

Spray Pam on the rest.

Aphids are very common in summer on waterlilies, water lettuce and other aquatic plants.

Can you use aphids spray like what you would use on your rose bushes?