What causes cupped crinkly leaves on cuke plants?

[Taiji]

Every year some of my cuke plants get this cupped crinkly leaf look. Plant on the right is pretty healthy, but the one on the left is not. Planted at same time; same batch of seeds. Looked for insects of some kind on upper and lower side of leaves, but nothing. I think they usually grow out of it, I'm hoping. Nutrient deficiency maybe? Watering is consistent.

[JONA]

Hi Taiji,
Just a quick question. That looks like hay or straw that you have around your plants.
Where did you get it from?
Cucumbers are exceedingly sensitive to any form of weedkiller. Especially the hormone based ones. 24D ..etc.
Even the slightest hint will cause leaf distortion.

[jal_ut]

Cucumbers are warm weather plants. I suggest getting some seed and plant a row of cucumbers in your garden plot. One seed every 8 inches in the row. No mulching or thinning will be needed.

[imafan26]

The puckering looks like aphids or Thirps/mites. If you did not see the aphids under the leaf then maybe they are thrips or mites. Those are much smaller and you would need magnification to spot them. There is usually some stippling when the leaves are older.

The only other thing it looks like is phytotocity, not so much from herbicide residue but from soap residue. If you mix soap spray too strong or use it on some plants like peppers and occasionally cucumbers, it can make the leaves pucker like that.

[Taiji]

Thank you. Actually the hay is alfalfa that they feed horses here. Good to know about the hormones, but my cukes only were recently mulched; the crinkly leaves appeared on the first new leaves before any mulch.

The cukes actually are planted in a row well spaced outdoors in the garden. The pic doesn't show the whole row. It's just that the leaves most always start out with that crinkly look.

I'm leaning toward mites or thrips too. I didn't see any aphids, but I think there could well be something hiding in those little crinkles. I sprayed top and bottom with alcohol. I hope it doesn't hurt the leaves. The only think bad about it I can think of is if leaves have some kind of natural protective coating on them that the alcohol might dissolve?

Didn't use any soap on these plants yet. And yes, some of my pepper plants seem prone to this too almost every year.

[JONA]

if you can't find any pest activity....although thrips can be the very devil to spot.... another problem could be Beet Curly Top Virus.

Just to add yet another spoke in the wheel!

[Taiji]

Hmmm. I'll have to look that one up.