How to organically control horn worms on tomatos

[dwilly]

I live in a suburban area. I am picking new horn worms multiple times daily off my leaves B4 they grow big and start devouring my plants. My son lives out in the country and has no problem with horn worms. Any help appreciated.

[hendi_alex]

Yep, pick and squish. Absolute best organic solution. Some years we have wave upon wave of the worms, but most years it just takes a careful eye while walking the garden. Corn ear worms are a far greater problem for us. The worms are harder to detect before damage, and they will bore into every tomato in a cluster, ruining the whole batch.

WRT horn worms, be sure to leave any worms that have the white parasite egg cases on their backs. Once infested, the worm stops eating very quickly and provides the next generation of parasitic wasps to take care of many worms for you.

[tomc]

There is an itty bitty wasp that lays eggs on hornworm, you know she's been working them when you see the pupae as little white bindles on the hornworms' back.

When you see those, that hornworm is toast. He's not going to eat any more, leave him on the tomato plant to hatch out the next generation of predators.

Pick off any others still busy eating...

[rainbowgardener]

tom and hendi are right. The teeny little wasp is called a braconid wasp. Hornworms that have been parasitized by it look like this:


https://thumbs.dreamstime.com/z/tomato-h ... 881436.jpg

If you see these, leave them. The worms are already dead or dying and the pupae will hatch out the next generation of braconids.

You can attract braconids and other beneficials to your garden by planting things that have nectar bearing flowers in tiny florets. This includes sweet alyssum, chamomile, feverfew, catnip and buckwheat. When allowed to produce flowers, dill, fennel, parsley, and other members of the carrot family also attract braconid wasps. I grow lots of this stuff in my garden and I never see a hornworm that isn't already parasitized. Go braconids!

[feldon30]

Hit everything with BT (sold as BT Worm Killer concentrate by Green Light in Austin, TX). You'll take care of hornworms as well as leaf rollers and fruitworms, and it's completely organic.

[rainbowgardener]

Interesting. Feldon is exactly right, that BT (bacillus thuringiensis), a bacterium that affects only some caterpillars and insect larvae, is completely organic.

We now have illustrated what I think of as three different types of gardening/farming:

What we tend to call conventional/ traditional, but has only become "traditional" in my lifetime, since WWII. I call it chemical gardening: Gardening in monocultures ( a field that is all one crop, e.g. corn), plowing/tilling, synthetic fertilizers, chemical herbicides and pesticides.

Organic gardening- Probably still monocultures, probably still plowed/ tilled, uses things like compost / manure/ compost tea instead of synthetic fertilizers, uses hand weeding or things like vinegar, citrus for herbicide, Bt and things like garlic-pepper spray for pesticides, no synthetic herbicides and pesticides.

What I call ecological/ natural gardening, related to things like permaculture and biodynamic gardening: No monocultures, very diverse plantings, no tilling, composting in the field, mainly using only what comes from the field and mulch and cover crops, companion planting, trap crops, interplanting, beneficial insects, use of birds, toads, ducks etc to control pest populations, chicken tractors for fertilization...

So the chemical gardener sees the hornworm and reaches for some kind of poison spray. The organic gardener sees the hornworm and reaches for the Bt spray. The ecological gardener sees the hornworm and tries to figure out how to adapt the garden ecology to keep everything in balance, and probably doesn't spray anything except water.

Of course most of us exist somewhere along this continuum and are not perfectly any one 100% of the time!

[hendi_alex]

Plan longer than a day or two and it will be too late as the tomato worms will strip every single leaf.

[JayPoc]

Plan longer than a day or two and it will be too late as the tomato worms will strip every single leaf.

Yeah...the suckers grow exponentially. Every year I go from none and no damage to caterpillars bigger than my thumb and major damage just about overnight. Haven't seen any yet this year, or many of my other scourge which are aphids...knocking on every wooden object in sight...

[rainbowgardener]

Yeah once they are in your garden is a little late to think about planting nectar flowers to attract braconids and other beneficials - but you can start doing it now for next year! In the meantime, they are big and slow and easy to hand pick; you just have to look close to spot them.

[JayPoc]

Yeah once they are in your garden is a little late to think about planting nectar flowers to attract braconids and other beneficials - but you can start doing it now for next year! In the meantime, they are big and slow and easy to hand pick; you just have to look close to spot them.

This is where small children come in. A couple seasons back, I told my then 6 year old son that I'd give him a dime for every one he found. I owed him almost 3 bucks after the first two days!

Oh, and by the way. I've NEVER found one that had been parasitized...

[applestar]

So far my best horn worm specialists in the Garden Patrol are the braconid wasps, paper wasps, and male cardinals. Its possible house wrens may be catching the really early instar caterpillars -- at least they often have green caterpillars in their beaks. Paper wasps hover among the foliage and crawl everywhere on the plants looking for meals to feed their babies.

I watched the cardinal stalk, aim and pounce on the horn worm -- twice -- last year. Of course I never saw the thing until the lime green limp body was clearly obvious in his beak.

I've posted the photos of braconid victims before. I can resurrect the thread again if you like.

I only spray Bt as last resort and very carefully because I'm just as avid about identifying all the different butterflies and moths in my garden as I am about everything else. Then I try to grow more of their larval host plants. Many of their caterpillars are harmless and their eggs are laid singly. It's the mass dumpers like army worms and cabbage moths that can be very destructive.

If you are getting a lot of hornworms in your garden, consider what kind of night blooming flowers you have -- many night opening cucurbits (like gourds and melons) and ornamental flowers attract night flying moths including hornworm Mommas. Also "moths to flame" as the saying goes -- is your garden lit up with night illuminations? -- neon signs to signal the moths to come to the all night red light district and daycare?

[feldon30]

So the chemical gardener sees the hornworm and reaches for some kind of poison spray. The organic gardener sees the hornworm and reaches for the Bt spray. The ecological gardener sees the hornworm and tries to figure out how to adapt the garden ecology to keep everything in balance, and probably doesn't spray anything except water.

I do see what you are saying, and there is plenty of "shoot first, ask questions later" from gardeners who want problems solved quickly.

As an ecological gardener, you would need to patrol the garden several times a day without vacation in order to catch hornworms before they become a major problem. A single worm can strip a 4 foot tall tomato plant to the ground in a day.

I like BT because it is completely innocuous to beneficial insects, and only affects caterpillars and worms. If you do not want to negatively affect butterflies (adult caterpillars/worms), then a butterfly garden filled with attractive plants such as parsley, dill, butterfly bush, etc. a safe distance from the main garden would be prudent. I'm actually considering one!

Tomato fruitworms and leaf rollers are hard to control in places of dense foliage. In this situation, a choice between "organic" and "ecological" would be a difference of plant spacing and/or pruning practices. An ecological approach would require much more room between tomato plants to ensure that there is 0 chance that bugs can get a foothold. In my garden, I can plant rather closely and then periodically hit the plants with BT and any worms that try to feast on fruit or leaves won't stick around long enough to cause a problem. In a densely planted garden, the ecological approach would require exhaustive searching for damage to fruit and leaves on all parts of plants on a daily basis.

[Lindsaylew82]

Found 3 more hornworms today. 2 dinks and a fatty!
Here's fatty!


I go about hand picking like this. (I have HORRIBLE ADHD, so this is hard for me.) I walk through the garden and just do a broad check. About 10 minutes if I don't have my camera. Anytime I'm just admiring, I always have a cup of soapy hot water and some type of grabber. My grabber of choice is hemostats and I also use a plastic clamp for bigger bugs. If I see something during the walk through, it gets the spa treatment. I ALWAYS have the green cup of death with me.
Next, I look under ALL the quash plants. Raised rows help SO much with this! Find, spa treatment, find, spa treatment...yaya...
Next I start tying the tomatoes and pruning. This is how you really get to look closer. I look for 2 things on tomato plants. Poop and holes. If you see either of those, there IS a worm. Army worms are more numerous here than THW. Give them all the spa treatment.

Do a final walk through. Give the stragglers the spa treatment. If I see eggs, I roll them off into the suds.

I have a large garden. It requires hand picking nearly every night. I don't look at my time in the garden as work. It's more like meditation and relaxation for me. ( Except for slugs...they piss me off pretty bad.) Unless I have a really bad infestation, hand picking is just part of my daily garden duties. All in all, it takes me an hour to do all of my 45x60 garden.

I've not used BT, but I wouldn't feel guilty using it as a last resort or if I had what I felt was an unmanageable infestation.

I have seen host THW, but I usually get to them before the beneficials. The ones I'm pulling off are pretty small. 1/2-1" long.

[rainbowgardener]

"As an ecological gardener, you would need to patrol the garden several times a day without vacation in order to catch hornworms before they become a major problem. A single worm can strip a 4 foot tall tomato plant to the ground in a day"

Nope. As an ecological gardener, I never have to worry about hornworms. Whenever I see one, it has already been parasitized.

[applestar]

Yeah, and parasitized ones don't eat much. It's more like -- one day, huh, something's eating this plant, and -- next day,hmm something is definitely eating this plant... OK look around... (Maybe nothing. Let it go... Sometimes that's the end of it. Somebody picked it off the plant first.) -- *or* third day, OK this green tomato has a bite mark so look harder... OH THERE it is! covered in faint grey spots where the wasps are going to come out any day now (or already carrying the pupae)

Also, Like I said, I hear a commotion in the tomatoes and then see a bird triumphantly carrying off it's prize. Wasps buzzing more than usual in the tomatoes could be them hunting too. I just don't see many hornworms period.

Though I'd love to hear from the more southern Gardener's if this holds true for them too. Maybe we just don't get as many where the winter freezes.

BTW paper wasps seem to be attracted to wooden and bamboo stakes. They are always scraping them off for the fiber. In the beginning of the season, I have to get used to the constant gnawing noise in the garden.... I usually don't know where their nests are though (and I don't tolerate them near high activity areas).

[Lindsaylew82]

I've seen them parasitized, but the ones that I've seen like that are large. The ones I'm picking off are small. Big horn worms do BIG damage. Not a little leaf here, I little leaf there. In SC, they can defoliate and entire plant in 3 days. No kidding.

I have a VERY heavy garden patrol. I frequently see swarms of Tach's and Brac's. The BEST garden patrol member, is ME, when it comes to THW... The same is true for army worms. If I see a leaf with a hole, or a poop trail, I'm on it like I'm lookin for the last word of a word search puzzle! Up, down, across, back, and diagonal... Like Liam Neeson in Taken...

Hahahahaha

image.jpg (16.4 KiB) Viewed 1708 times

In all seriousness. If I saw one on a plant that wasn't doing well, I'd let it go, and watch it.....very closely.

I don't normally see many...2-4 per year. But I've seen 4 already this year. So it's going to be a heavy year for them here.
I have some pretty heavy woods around me and 100's of acres of pastures that are filled with Queen Anne's lace. I'd say I live in the country, not in the city.

[feldon30]

"As an ecological gardener, you would need to patrol the garden several times a day without vacation in order to catch hornworms before they become a major problem. A single worm can strip a 4 foot tall tomato plant to the ground in a day"

Nope. As an ecological gardener, I never have to worry about hornworms. Whenever I see one, it has already been parasitized.

Must be nice.

[rainbowgardener]

Re: I've seen them parasitized, but the ones that I've seen like that are large.

That is true, by the time they look like the picture, they are big worms. But some people have called the white things egg cases. They are not, they are pupae/ cocoons. Long before it got to this stage, the adult wasp laid her eggs inside the hornworm. They hatched out into larvae and started eating the live worm from the inside out (eww !!). Only when they are mature enough to pupate do they emerge and form the cocoons. So that poor hornworm has been quite slowed down for a long time and did not do a whole lot of damage. Eventually you will see the white pupae with holes at the top. That means the adult braconids have left their childhood home and emerged to start the process over.

Re JayPoc saying he had never seen a THW parasitized. Do you grow the flowers to attract the adult braconids? The adults are nectar eaters.