Cross-striped cabbage worm. The leaves supply nutrients to the plant, so if they are decimated, it stands to reason that you will get less production out of it.

Looks like a western yellow striped armyworm to me, but the picture isnt quite clear enough to tell. If there is one, there are hundreds closeby. The adults lay a mass of hundreds of eggs, two generations per year. And in my experience they are opportunistic feeders with few preferences, meaning they eat just about anything (at least in my veggie garden with flowers).

Although Japanese and June Beetles are members of the same family, Scarabaeidae, no one should think of them as also known as, aka, because they are not. Those larva are members of that Scarabaeidae family of beetles of which there are some 30,000 different beetles. The larva feed on organic matter in soil during some growth stages and if population numbers are high they can be quite destructive while others are, Japanese Beetles, are more destructive as adults. The best time to apply controls, if necessary, is just before the eggs hatch in late July to August, when the larva are most susceptible. Those that overwinter pupate in the spring and emerge as adults to begin the cycle again in late May thru June, but they do not ingest any food then. What to use for control depends on which of these beetles you have. There are biological controls, Milky Spore Disease (Paenibacillus papillae) for the Japanese Beetle larva, parasitic nematodes for all of the larva, and some quite harmful other poisons available. Talk with the people at your counties office of your state universities Cooperative Extension Service about the best control strategies for your area.

Ubro: I am really not sure which kind of caterpillars they are. vgkg: That kind of sucks if that's the case. Moses: Thank you I will check into that. Is this something that you just spray around the tree trunk or the whole tree. I have really tall oaks too so will not be able to reach any leaves. Gardenangel: Thank you and I will check your recommendation out as well. Same question, do you spray just the trunk or the whole tree? I just remember seeing them climbing up the trees in numbers. My father wrapped the tree and there were a lot that crawled right up to it and wouldn't go any further. So they had to be coming from below. I am really not liking the idea of spraying. If I was to use petroleum jelly on some kind of wrap around the tree, will it hurt the tree when it rains on the jelly, like would any toxins drip down out of the jelly?