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The Armyworms Are Here: Don't let them get your greenhouse tomatoes 

If there's a greenhouse in your backyard still going, and you're finding holes in your tomatoes the following may shed some light on what's going on—if not—save it for next growing season.

click to enlarge 16.45-natural-world.jpg
If there's a greenhouse in your backyard still going, and you're finding holes in your tomatoes the following may shed some light on what's going on—if not—save it for next growing season.

"Jim!" My wife, Sue, exclaimed one morning after she opened the greenhouse and starting watering. "There's something eating holes in our tomatoes!"

Sue enough, when I went to take a look, there was an obvious finger-sized hole in the top of a beautiful green beefsteak tomato growing on the vines we have strung up in the greenhouse; and we began the search for the beast causing it.

 


Every night—from that first discovery—we went out to inspect our dear, dear tomato plants by flashlight, hoping to spot the culprit. Three nights went by before we found whom it was; and we caught him in the act! But, when we did, we didn't know who it was. It was/is a rather large caterpillar, about the size of a child's little finger, greenish gray in color and wearing camouflage that allowed it to blend in with the shadows cast by our flashlight on the tomatoes.

 

I thought first of the tomato-hornworm; the larva of a beautiful nocturnal hummingbird moth. But it wasn't green and there was no "horn." (I find it difficult to kill them, they're so handsome as larvae and adults.) It was much too large to even be a relative of the many species of aphids we see sucking the sap out of our plants, but it did (sort of) look like a cutworm.

I quickly photographed the culprit in the act of chewing another hole in another tomato. It wouldn't be so bad if the critter ate just one tomato, but no, it has to go from tomato-to-tomato leaving a hole in each—and it leaves some of its frass (poop) in the hole to add insult to injury.

Luckily, I knew just who to ask when it comes to identifying unknown caterpillars: Dr. Jeff Miller. He wrote a book about caterpillars, and will likely be the new head of the Horticulture Department at OSU. Jeff and the Anderson Family have been friends for so many years, I can't recall when we first met, but I'm pretty sure the catalyst was either butterflies, moths or beetles.

Jeff was in charge of an OSU moth survey back in the ‘90s when the gypsy moth population exploded in the Cascades. The United States Forest Service wanted to spray BT to "manage" the moths, which would have killed all lepidopterans (moths and butterflies).

But that wasn't a good idea, as our native and rare Townsend’s big-eared bats eat moths, and our biological lifeguards could see the danger of BT killing off the bat's food supply. Jeff got busy and started a night-trapping plan to see what/who actually lived in that part of the Cascades, and hired my son, Reuben, to run a set of light-traps.

I was hoping that when Jeff hired Reuben—who was in high school at the time—he'd get bug-fever and look at entomology as a career, but it didn't take. He did, however, trap a beautiful, large adult silk moth one night up near Iron Mountain that turned out to be a new species for Oregon.

Anyway, Jeff looked at my moth photo and pronounced it to be an army/cutworm. When I started looking up armyworms on the Internet it about scared me to death: they are very good at eating everything we want to eat.

I thought,"What malice have we thrashing through our greenhouse?" Especially when the mature caterpillar can reach to two-inches long and has no conscience about boring holes in our tomatoes!

Here's what Wikipedia has to say about them: "The armyworm's diet consists mainly of grasses and small grain crops. An infestation is hard to detect as the caterpillars migrate to new feeding areas in the cool of the night. When the caterpillars near maturity, they can lay waste to an entire crop in a few days."

Then, this statement really gave me the heebe-jeebies: "In mid-April 1999, an army worm infestation started in southern Ethiopia, spreading into the north the following month and into the Jubba Valley of Somalia in early May. Similar outbreaks affected the Rift Valley Province of Kenya, and parts of Uganda at the same time."

I'm still wondering about a possible outbreak in Oregon some time down the trail.

In his response, Jeff didn't help.

"There are a few hundred of armyworm/cutworm species in the US, in fact hundreds of species around the world. There is just no getting away from them," he said.

That last sentence was really scary, I figured our poor tomatoes were doomed.

So, Sue and I are patrolling the greenhouse every night. So far we have placed four of the gluttonous cutworms into captivity of a large soil-filled jar with a few of our (sob) holed tomatoes. We want to see what the adult moths look like when the caterpillars metamorphose.

Our plan is to continue to physically remove the larva from the greenhouse and their chosen food-supply. We will NOT use chemicals of any kind to rid the greenhouse of the pests. It's against our personal religion to use chemicals on anything we grow, or to poison any pest(s) from our premises, whether it be plant or animal.

If our persistence to collect the pests is successful we'll (hopefully) continue to enjoy of our delicious (organic-grown, Mittleider) tomatoes. Hope you have our patience, too, if these little creatures have infested your greenhouse. And that your tomatoes keep it up just a little longer!

Aphids

Aphids are tiny, green soft-bodied insects that attack soft new growth on plants. Natural predators of aphids include lady beetles, damsel bugs and predatory wasps. Non-chemical treatments for aphids on tomatoes include a strong spray of water and brushing aphids with cornmeal or talcum powder. Persistent aphids may need to be sprayed with vinegar water or soapy water to completely eradicate them.

Tomato Hornworms

Tomato hornworms are large, green caterpillars with a hook, or horn, on their tails. They are the larvae of hawk or sphinx moths and grow up to four inches long. They are voracious feeders and strip the foliage off tomatoes quickly if not controlled. Bacillus thruingiensis is a natural control, and parasitic wasps lay their eggs on the large caterpillars and kill them.

Cutworms

Cutworms are large, olive green and brown caterpillars that get up to two inches long and are very destructive. They can be handpicked and dropped into a bucket of water. Protect newly planted seedlings with plastic or cardboard collars around stems pushed slightly into the soil.

Armyworms

The armyworm's diet consists mainly of grasses and small grain crops. An infestation is hard to detect as the caterpillars migrate to new feeding areas in the cool of the night. When the caterpillars near maturity, they can lay waste to an entire crop in a few days.

Photo; Jim Anderson

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