Please help me identify these white spots/area on my kale leaves and please use the zoom button to zoom in. The photos are high resolution.
My wife doesn't like these white spots which are exclusively on the back of the leaves. So, she ends up throwing these leaves. Can we clean the white spots and eat the kale?
The white spots are on every 4 out of 5 leaves.
Thank you.
Looks like a combination of whiteflies and early-stage white mildew infection to me. I usually get both when I try to grow kale in Seattle, but not this year due, I presume, to unusually hot and dry conditions.
Of course you can clean as best you can, and eat it. There's nothing toxic about either of those afflictions, and I doubt the taste would be affected either, at least if it's cooked rather than raw.
Identification starts with getting as much information using all senses. The photos are great, but we cannot tell what happens if you rub on a spot, does it come off or is it damage to the leaf? Do you have other brassica type crops close by showing similar effect?
Then we can speculate on cause: starting with simplest, is it perhaps an evaporated deposit? Since it is not on the top of the leaf maybe it was washed off. Do you splash plants with hard water, say from underneath with soaker hose?
There is a fungus that can attack kale and similar crops called white spot fungus. I will let you look up the details on that, they are quite detailed and don't bear repeating here. Only check this if the simpler explanations don't apply.
Some insects can attack the leaves and leave deposits, however if it was aphids the honeydew regularly turns black as the sugars grow their own fungi. The whiteness of the spots argues against this. I hope this gets you started.
I've seen this before on plants. White flies only live on the back of leaves. Until they overpopulate, then they're on both sides. To get rid of whiteflies all you need to do is hose the leaves twice a day for 3 days. Hose the back sides where the Flies are. It knocks them down onto the ground where they die. Then their eggs that hatch, need to be hosed off. That may take another three weeks of hosing, just daily. Hose while the sun is out, and the leaves will dry before nightfall. If you hose before you see too many of them, you'll stop the colony from growing, and spreading to other leaves, and other plants.
The other issue with the leaves is the white fungus growing on the leaves. Or it might be part of the whiteflies nesting. Either way if you use water that has been chlorinated by the city then that will disinfect the fungus which will die. This will leave you with clean leaves of both white flies and fungus. I suspect it's not fungus but a function of the whiteflies nesting. I just don't see enough whiteflies to create such expensive nesting though. So it could be a fungus. After the hosing and washing in the sink it should be safe to eat. Don't try a really big meal at first. Just try it small bite. Wait 24 hours. Then try to bites. Go slow to be safest. Do read up about white flies and get pictures of what they look like and what their nesting looks like. Then enjoy the kale. By the dark green it looks like it's very excellent. You must have very good soil.
For your existing crop you can just wash it in the sink. Once it's free white flies and the white thready stuff it should be safe to eat. Cooking it will certainly make it so. Adding olive oil will particularly disinfect it and make it safe.
