07/17/2012 found these Caterpillars (Horn-worm) feeding on my Tomato Plant
These caterpillars are so big (three inches long or more) that it would seem to be easy to control them just by picking them off. And so it is, sometimes. The problem is that their pale green color provides excellent camouflage, and the nymph and larval stages are far smaller and less obvious. If there are only a few, picking them off works well. (One site suggests spraying the plant with water, causing the caterpillars to, and I quote, "thrash around," giving themselves away.) If there are more than a few, other measures may be called for. One of these is Bt, Bacillus thuringiensis, an organic treatment that can control numerous other problems as well.