Q.There Are Tiny Black Specks On My Lettuce Leaves That Will Rub Off. No Evidence Of Damage.Is This Caterpillar Poop?
I have several lettuce plants and they are on most of them. Some specs larger than others. Could not find any caterpillars. Also no leaf damage.
Certified GKH Gardening Expert
If it wipes off, it could be some sort of insect poop. If not, I would be more inclined to say that it is an infection.
Here is an article that will help you to grow lettuce: