Lambsquarter is one of our weeds, so you might be curious as to why I'd be interested in its health and what afflicts it. The reason is because it's affliction is spreading to wonderberries, and making the whole plants lose color (not just on the spots; the color fading only happens on the plants with leaves like this).

My first thought was leaf miners, which is probably true, but these are some pretty voracious leafminers if that's the only problem, and to my knowledge, leaf miners don't make unaffected parts of leaves, and the stems fade in color.

Does anyone have any idea what this is? Or, is it just a voracious case of leaf miners that wonderberries especially just don't like? Or, are there diseases that leafminers are known to spread, such that this might be two problems?

The problem seems to coincide with recent rains (warmer rains than we usually get).

Sorry, I don't have any pictures of afflicted wonderberries (I pulled them all up too soon, because it was spreading pretty fast among them; all the afflicted wonderberries had lambsquarter weeds with them). You can see some healthy-ish wonderberry volunteers below with the lambsquarter, though--I guess some are a bit chlorotic, but not enough to show the issue.

It does look like classic leaf miner damage to me, of the sort you get on beets and chard so same family as lambsquarters I believe. I'm not sure if there is disease involved but that's possible I guess.
The big issue with the leaf miners is that the dead leaves drop to the ground where they then pupate in the soil and make more of themselves. So you may want to gather and burn or otherwise dispatch and destroy the leaves that they're feeding in.
Sorry to hear about your wonderberries!

In my past run ins with leaf miners I have surmised that cutting the leaf off at first notice will stop that miner from evolving into the little kamikasi fast moving small black critter that lands and pierces the next leaf ,leaving some future babies,and of course any kind of disease if present from the critters past injections.There are some sprays that carry neem,bonide etc.It will affect the fly as it lands and gets the chemical into their system and kills it.Also a soil drench in the bed underneath plants will kill the little ones.White flys carry disease the same way but underneath the leaf.Try not to spray during high sun times,tends to burn leaf.Check the life cycle charts of these critters.

Bower wrote: ↑Tue Jun 07, 2022 6:06 am Sorry to hear about your wonderberries!

Thanks. No worries, though. There are still plenty of plants. The leaf miner damage seems to have stopped progressing with the cessation of the rain, so far. I don't see any new leaf miners by the wonderberries on my garden map.

The wonderberries I started in foam cups don't seem to have been affected.