This is a tomato hornworm:
They love to eat tomato plants and can be rather damaging, defoliating large areas very quickly. They’re hard to spot, but their presence is easily determined by (a) large areas of missing leaves and (b) piles of increasingly large caterpillar crap on the ground or cupped in remaining leaves. For example, look at the classic example at the end of the upper right critter in the photo below.
Over the past two weeks, we’ve seen an explosion in their numbers. Our friends down at Happy Hollow Farm (an Organic CSA in Moniteau County) have seen the same. Here’s one morning’s bumper crop:
The best way to control them is simply to spend some time hunting them down, and picking them carefully off the plant. Then you can either step on them or otherwise squish them, or in our case feed them to the chickens, who love these fat, juicy, protein-laden treats. Nothing like watching a hungry hen tear into a 2″-long caterpillar. Revenge…
If you have trouble finding them on your plants, which is understandable since they’re very well camouflaged, learn to follow the scat trail. Look for ever-increasingly-sized piles, and look especially for the green piles, which are fresh (they turn black as they age). Also look for fresh wounds on the plants, rather than those that have started to scab over. These will help you narrow down the appropriate search area, and then you just have to train your eyes to see the caterpillar, usually hanging from a partially defoliated stem. The other trick is remembering which damaged areas you got them from yesterday, and which areas are fresh since then.
I prefer to pick off the whole stem it’s hanging from rather than just the caterpillar, as they’re very good at intentionally sliming you if you grab them directly. Why get gooey when a boot or a rock can instead?