Hornworm war....Help!

[Ksk]

Hi Everyone,
I am at war with hornworms!!!!! There are more this year than I have ever seen. I am using a straw bale garden for the first time and the plants are producing like mad so are quite healthy. I use soaker hoses and it seems to work quite well. In the past I have picked them off but never this many. I use organic methods but the garden is technically not certified organic. Also, lizards eat the worms near the bottom but can't reach the top of plants so I don't want to hurt them.

Two or three times per day I go out and pick off hornworms that at this point are quite small. I also hunt for eggs to reduce the population. So far I have held chaos at bay but am losing ground as the plants are getting so large. I am thinking of using BT for the first time due to the sheer volume of worms. The plants are too big to cover at night. I live in the high desert and moths abound.

1) If I spray BT on my tomatoes how long will it last?
2) Is it OK to do a general BT spray over all the plants or do I need to spray back and front of the leaves?
2) Do worms eat tomatoes or just the leaves?

All ideas welcome.

We are planning a four day trip so I can't very well expect my friends to visit and hunt for hornworms while I am gone. That would be some friend.

[rainbowgardener]

Yes, when your tomato plants are fruiting, the hornworms love the fruit:



This is what the fruit will look like after the hornworm has been eating it:



It won't help much for now, but there is a tiny, stingless wasp called a braconid that parasitizes them. If you ever see one that looks like this



Leave it alone, those are the cocoons of the braconids. The adults will hatch out from those and start a new generation. The larvae feed on the caterpillar. The adults are nectar eaters. To attract them to your garden, you have to have flowers they like, which are usually ones that have their nectar in tiny florets. I moved a couple years ago. Where I lived before and had been gardening a long time, I hardly ever saw a hornworm that wasn't already parasitized. Those flowers include sweet alyssum, chamomile, feverfew, catnip and buckwheat. When allowed to produce flowers, dill, fennel and other members of the carrot family also attract braconid wasps. Also yarrow, tansy, caraway, coriander, cosmos, zinnia, edging lobelia, lemon balm, pennyroyal, marigold.

[imafan26]

I saw the hawk moth on my window and in the garage where it usually lives and the bagworms are attached to the walls all over the place outside. I will have to do another sweep. I did see a fiery skipper, but the garden patrol is keeping things under control, I haven't seen any caterpillars or beetles. I even got a present left for me on the wall ( a dead mouse) by the cat that likes to spend days in my garden. It is the third one this year. The cat must belong to someone, she never eats her kills.

[Ksk]

Thanks, This forum is great. The damage in the picture is what I am seeing inattition to leaf damage. At least there is not yet another pest showing up to eat these plants. I may try planting the dill but hope I it is not too late here. Gratitude.

[rainbowgardener]

Well you said you are in a hot climate, so maybe you have a long growing season. Planting some dill and other stuff might draw some braconids soon enough to help prevent / reduce a second generation.

But you need more than one dill plant (and the dill has to flower). Several plants each of several types from the list will work a lot better. So mainly this is a solution that is more likely to be helpful next year and even more in following years as you gradually build up a braconid population

In the meantime, if you start seeing full sized hornworms (like 3-4" long or so and fat) then pretty soon you can start checking the soil around your tomato plants for these:



After the hornworm gets full grown it drops down, burrows into the soil and pupates. The pupa is as big as the full grown hornworm. By winter they will be 4 to 6" deep in the soil, but in late summer they will be pretty near the surface. Just dig around gently, so as not to injure your tomato plant roots. Any one that you dig up and get rid of is one less hawk moth/ sphinx moth , which could represent as many as one thousand eggs/ caterpillars.

[Ksk]

Rainbow,
Thank you. The photos are most useful.