I came across this caterpillar (?) infestation on the underside of an apricot leaf. Any idea what they are? I've never seen this before. I noticed discoloration on the top of the leave and discovered this when the leaf was turned over.
Don't know what they are but I suggest you squish them.
mytrees, I do not know what they are but if I wanted to find out I would keep a few of the caterpillars in a jar and keep them supplied with fresh leaf material daily. Soon they will pupate and later they will emerge as adult butterflies or moths and be easier to identify. It sounds like if it is the one leaf so just keep looking over your plants. You have done an excellent job of observing something strange and pursuing the cause.