From unh.edu website: These are not spores, insects, or eggs, as many people believe. They are trichomes. Trichomes are hair-like outgrowths from the epidermis of the leaf, and many plants (including spinach) produce them. Trichomes come in all sorts of shapes and sizes, and have different purposes. In the case of spinach, if you look closely with a microscope, you can see that there is a little hair that comes from the leaf surface, and a big glob at the end.

Lucky you! It is fun to watch, and really, just let them get on with it. This year I noticed that the ones that sunk actually did hatch too, I think because overall the pond was warmer this year. Whatever happens, they will gradually eat the stuff. They do eat constantly! Go out at night with a torch, and you will see some of what really lives in your pond. When they get their legs, they will need to safely be able to get out of the pond and live on land for awhile (or they drown). So make sure they can get out of the pond, and not onto paving slabs (poor things are so delicate they stick to the slabs and fry). The froglets are quite amazing (tiny perfect frogs) and will need to find shelter under plants, rocks, etc. For awhile you will be spending your time in the garden looking down before each step!! Only 4 in 1000 will make their way to adulthood to spawn themselves. So you can never have too much frogspawn, and anything you can do will help! They start off as algae eaters, but later become carnvivourous and will eat one another. Mostly everyone else eats them including newts & frogs, dragonfly nymphs, but they do survive. Bigger fish though much their way through a lot of tadpoles. There are some really good information websites on frogs and other pond life--just google and you will find! The bugs are incredible too, like the caddis fly larvae and their amazing houses, and damselflies and dragonflies. The latter leave their papery perfect exoskeletons behind on leaves before they fly off. So welcome to the wonderful world of ponding. You may find yourself making a second, bigger pond.... Chip

As mentioned, pictures aren’t very clear but sometimes pictures just can’t capture the situation. I sorta see what the previous poster describes, but then a see actual white flecks not sap like....is it under the leaves too? And you said they’re “white” & not milky or clear? Looks like possibly mealy bugs a little to me., esp w the white on the leaf stem too. They don’t look like insects at all but white fuzzy spots, initially very tiny but if not caught quickly, it will develop into small white fuzzy looking mounds sort of & feel a little like thick sticky spider webs. And spreads terribly! If they start getting into the leaf axils & stipules on a pothos or heart leaf Philo, etc, it’s a real horror to get rid of! Really hope the other is right but until you know for sure, isolate it immediately & start checking all nearby plants. If you find it anywhere else, there’s your answer. If you don’t, could still be mealies but at least hasn’t spread & keep separate until treated several times & you’re certain they’re gone. Check others regularly too in the meantime~it’s crazy how they can pop up across the room but not in the neighboring plant. Google it & see what you think. Truly hoping I’m wrong, but took a moment to share my thoughts since it’s such a nightmare~if rather waste a few minutes & be wrong instead of staying quiet & it’s covered in a couple of weeks. Oh, they suck sap thru the plants skin, so they start causing serious damage too, it’s not just a surface nuisance. Good luck~

It might be because of powdery mildew (Although it might be something else, I'm not an expert on things like this). Try to look further in because there is probably a high chance I am wrong because it looks a bit different from what I'm saying it might be. If it is because of a bug or something like that, then do whatever you need to do to prevent it from spreading to other plants or getting it off of that one. I hope you can save it!