Possible but not likely. When the moth lays her eggs they are in multiple locations on the plant. That doesn't mean they all survive to hatch but the odds heavily favor more than one.

There is no need to obsess over it though. A daily check of the plants is usually sufficient. You may miss one or two and get some damage before finding them but the average tomato plant will tolerate it and recover. And with practice they get much easier to spot.

Dave

It also helps if you cut off the damaged leaves, so that if there are others you can be sure it's from them, not the one you got.

Last year I had scores of them, well over 60 with a dozen plants, this year I've only found three. Guess they have good and bad years also.

Here is a link that might be useful: DFW Gardener

I've found 2 I plucked off, 3 more that had been parasitized (word?) so left them. Seems to only be on a couple of plants.

I watched the big moth lay the eggs. She flits around fast touching her rear here and there. My impression was that she was giving her offspring whole plants or at least plenty of space between eggs. There are wasps and flies that feed on them. I expected to find hornworms but I have only found one. My garden is dry and I have lots of red wasps coming to a stock tank in the garden. I have seen the tachinid flies attack big hornworms before and that is interesting to watch. I never see the wasps that make the little white cocoons.

Okay all, I will aim for diligent vigilance but no stressing.

@helenh: I know that lots of wasps are beneficials. But what is a "stock tank" for a garden? Is it something to attract beneficial wasps? what is it? where did you get it?

Tomato hornworms have found there way to my garden beginning yesterday. I found two that had done serious damage but were parasitized. I stomped them, not knowing until tonight that they carried tiny wasps to do in more hornworms. How do you balance the munching-crunching damage with the knowledge that they're carrying death for their fellow hornworms?

Thanks!

I've never seen a parasitized horn worm (still only the one fellow in my garden, still watching). But could you put the guy in a glass mason jar in the shade with a cutting from the tomato plant (like you would to raise a butterfly for a kid) so he's sequestered away from damaging your plants more but will host the wasps to maturity so they can help do in more critters?

Use a blacklight to find them. They glow under these lights!

Do they keep eating once they've got the wasp eggs on their backs? I didn't want to pluck them off either, but don't know if they're causing more damage. Seem to be hanging in there a long time (though 1 I saw yesterday really was just barely hanging on)?

@Capoman: A black light?! that is AWESOME. Does it work for any other critters? I'm having a heck of a time finding the bean leaf beetles on my bean plants. it would be dreamy if they were also day-glo

Thanks!

I tried the black light last night - extension cord, CFL black light in a shop light housing - and the hornworms did show up clearly against the tomato foliage. But they weren't like Elvis on black velvet type of glow-in-the-dark. At least one moth glowed too.