It has been raining for days and the leaves toward the bottom of my tomato plants are starting to look yellow. Then I saw what I thought were tiny little white bugs and figured I could just pluck them off. Much to my surprise they were part of, or attached to, a very large slug like creature that had suction cupped itself to the plant. What the heck is it, or are they? What can I do to get rid of it? I also found a smaller orange like slug that I smushed. Again, what is it and what do I do about it? And then, because things come in threes, I found droppings, on the leaves, that were the size of a small childs fingernail bed. hard to tell if it is bird poop or otherwise. This is the first time I am growing vegetables and these plants were hand cultivated by good friends. I want to make sure I do the right thing…too embarrassing to let their hard work, and mine, go to the bugs.
I wish you had sent a photo. The tiny white bugs you found were doing your job for you. It is perfect bio-warfare. They are the pupae of a type of parasitic Braconid wasp. The female wasp lays her eggs inside (using an ovipositor) the larva of a tomato hornworm, a common pest on tomatoes. It is the green sluglike creature you found. The larvae of the wasp eat the hornworm inside out, then pupate on the outside, the stage you discovered. The caterpillar then dies and the wasps mature and begin a new cycle. The Tomato Hornworm >is the caterpillar of a large moth, Manduca sexta or Manduca quinquemaculata. The larvae are identified by the horn at the posterior end and they attain a length of four or more inches and a girth equal to a human finger before burying into the ground to pupate. While in the caterpillar form, they can defoliate entire branches of a tomato plant as well as nibbling on the still green tomatoes.
So, if I have handpicked the two I saw, what should I do to prevent others from appearing and destroying the plant. I assume if there were 2 there are more, yes? I sprayed insecticidal soap on the foliage, but I am wondering if there is more I should do other than just keep looking for them and handpicking them off. On the web I read that I should not have killed the hornworm with the wasps, which is consistent with what you have said, but should I have left it there to have the wasps potentially kill other worms. I thought leaving them would just give them more time to eat the foliage and the tomatoes that they have already munched on. Also, once I harvest the last tomatoes, isthere anything I need to do to the soil to make sure that they are not going to be there next year?
Hand picking is, in our opinion, the best means of control. Watch for the telltale signs, nibbled leaves and droppings, then search for the grazer. You can sift through the soil to locate the large pupae, but adults can just fly in and lay eggs. A dilligent eye is the best form of control since we do not endorse undue use of pesticides in the garden, especially on produce meant for human consumption.