MEL said:

I live in Northern California. This year for the first time, shortly after
transplanting tomato plants they began to wilt. I pulled them up and found
a reddish colored worm inside the main stem. What are these and how do I
control them?

Could be European corn borers. Not much you can do once they are inside
the plant stems.

--
Pat in Plymouth MI

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)