Answer: It's possible you are dealing with pickleworms, though they are more common on cucumbers and summer squash. The adult overwinters in Florida and migrates north in spring, laying eggs on the developing cucurbit blossoms in early June. The eggs hatch in a few days and the larvae feed for two weeks first on the blossom, then burrow into the young fruit. Pickleworms reduce the yield of crops and make fruits inedible.
Here's a web site with more detailed information about the pest.
Because the pickleworm is the larvae of a moth, it can be managed using sprays of B.t., a biological control for caterpillars. To control an infestation, spray Bt in the early evening on susceptible plants, starting in June and continuing weekly. Row covers can prevent some early damage but have to be removed once flowers open. Begin the weekly spraying once you remove the row covers. Another possible control is predatory nematodes. For more information about these biological controls, visit the web site of Peaceful Valley Farm Supply, http://www.groworganic.com
(Here's the page with more info about the nematodes.)
Q&A Library Searching Tips