I've been wondering the same thing, I have a few leaves with the same damage. I wouldn't stress too much about it unless it's on a bunch of leaves. I'd buy a cheap 4$ bottle of some organic gardensafe insect spray from Home Depot or Walmart, dump the whole bottle in a sprayer then top off with water to dilute it. Soak your plants and even the vegetation around your plants every few days. That's what I did and it seemed to work pretty well. Next year I'll start doing this before I see any damage as a preventative. I'm sure there are probably better options than that cheap spray but for those of us on a budget it does just fine. Maybe another outdoor gardener with more experience would be able to identify from just the leaf damage and recommend something good for that particular insect. Good luck Sent from my iPhone using Grasscity Forum
garden safe the plant itself but break out the real shit for the surrounding area. http://www.essentialhardware.com/product_detail.php?pid=147387&gdftrk=gdfV28536_a_7c3119_a_7c11872_a_7c147387&gclid=CjgKEAjw286dBRDmwbLi8KP71GQSJAAOk4sjFPbU7K6SK0xxo_DrD2rScLNI304DJ5ZuEa_J5qyLGPD_BwE
Looks like mite damage. They are present on the bottom of the leaves. Use a magnifying scope to inspect the leaves. Use neem or another insecticide to kill them. They are common and destroy crops. Plants should be treated every three days until they are gone then at least once a week as a preventive measure.