When gardener's plant vegetables it's an invite to insect pests including the cabbageworm, should you decide to grow broccoli, cauliflower, cabbage, or any other vegetable plant.
It's a fact of nature insect pests will arrive in your garden patch no matter what you grow with each species searching out its host plant. Experienced gardeners know this and more importantly, know how to deal with these pests when they arrive. But the beginner gardener is in a learning curve as they wonder if anything they plant will grow at all. It soon becomes frustrating for them to see young healthy plants slowly give way to the munching and chomping of insect pests. This is not the time to give up but get even by knowing how to deal with this problem.
With that said, let's read on.
When gardeners talk about cabbageworms, most beginner gardeners usually imagine some sort of squiggly worm crawling on a head of cabbage. How do I know this? Because when I ask my beginner gardening students "what is a cabbageworm?" That was there most often response.
To be more precise, this vegetable garden pest is from the caterpillar family of which three species are of most concern to vegetable gardeners. They are the imported cabbageworm, the diamondback moth caterpillar, and the cabbage looper. All three are the larva from the adult diamondback moth or cabbage butterfly, (more accurately known as the imported cabbageworm butterfly).
When at rest, the diamondback moths wings come together forming diamonds along its back and hence its name.
Known as weak fliers, they do not travel very far but are readily carried by the wind.
The male and female live approximately two weeks and
females deposit eggs for about 10 days.
Photo courtesy Russ Ottens University of Georgia, Bugwood.org
The female butterfly has two black spots on each forewing and one in the case of males. The hind wing of each sex has one black spot and brown or black marking at the edge of their wings.
You may notice them in your garden fluttering about from early spring through late fall as they search for host plants to deposit eggs. The eggs hatch in three to seven days and the young larva begin feeding on the underside of the plants leaf.
The larva feed voraciously on both the outer and inner leaves often feeding along the midrib at the base of the wrapper leaves, or boring into the heads of cabbage.
Other indications of the presence of the cabbageworm species is large irregular holes in the leaves of vegetable plants.
The picture on the right is of cabbage looper larva having a meal on a vegetable plant leaf. When fully grown, its length is between 1 1/2 to 2 inches.
Photo courtesy of David Capparet Michigan State University, Bugwood.Org.
Other vegetables these insect pests favor are cauliflower, broccoli, Brussels sprouts, turnips, radishes, kale, letuce, as well as the mustard family. Fortunately, early grown cabbage is seldom severely injured because it reaches maturity before the cabbageworm population have built up significantly. However, the same can"t be said for late-grown susceptible crops planted around mid-July or earlier in parts of the country with warmer climate. More often than not, they will soon become the victim of these pests.
The imported cabbageworm (larva) usually grows to 1 inch and is velvety-green in color. They are slightly fuzzy and have a pale yellow stripe down the back, and when touched or prodded
usually remain in place. They also produce green frass (droppings) and prefer the center of cabbage heads as they grow larger.
The cabbage looper is smooth and green with several thin, white stripes down its back. When it crawls it arches its body in a loop (hence its name) then stretches forward. When fully grown its length is between 1 1/2 inches to 2 inches.
Cabbage loopers are late arrivals to your garden appearing in late summer.
The diamondback moth larva is green, not fuzzy and only grows to about 1/2 inch. When touched or prodded, it wiggles its whole body vigorously and often drops from the plant. You may find white silken cocoons with a green full-grown caterpillar nearby.
Photo courtesy Keith Weller, USDA Agricultural Research Service, Bugwood.org
Beside the three insect pests from the caterpillar family listed above, the following may also be an unwelcomed visitors to your vegetable garden. They are in no particular order: cross-striped cabbageworm, cutworms, cabbage web worm, southern cabbageworm, corn ear worm, gulf white cabbageworm, zebra caterpillar, and the purple-backed cabbageworm.
Natural predators of the cabbageworm and other vegetable garden pests are parasitic wasps, lady beetles, lacewings, ground beetles, spined soldier bug, (also called stink bug), spiders, yellow jackets and paper wasps just to name a few.
These and other beneficial garden insects are important for the survival of any vegetable garden and yet one more reason to grow an organic garden. The use of an insecticide to rid a garden pest will more often than not also kill beneficial garden insects as well.
To the right is a braconid wasp with its prey. In this picture the unfortunate insect pest is a gypsy moth. It is just as lethal with any of the caterpillar family and definitely a friend of any vegetable gardener.
Because common belief is that wasps are nasty and sting you they need to be avoided at all costs and destroyed when and where you can. But as most experienced gardeners will tell you, if left alone they will leave you alone. So get to know this little guy as its only interest is chasing down and making short work of bad insects in your garden.
Photo courtesy Scott Bauer- USDA Agricultural Research Service, Bugwood.Org
I hope you beginner vegetable gardeners have learned a little bit about this bothersome insect pest of the cruciferous family of vegetables. Now it is time to put some of that knowledge into action.
We've briefly mentioned your vegetable garden is alive with beneficial garden insects and we included a link for your to learn more about these "good guys" as well as related information about other insect pests. However, there is more we can do to prevent insect pests from taking over the vegetable garden.
One of the easiest preventative measures you can take is to grow cabbage as an early crop because they become established well before larva eggs are deposited and hatched.
Make it a part of your daily vegetable garden routine by scouting your vegetables regularly for presence of larva or freshly deposited greenish brown frass (droppings). And of course, the most obvious indication of their presence is damage caused by chewed holes in your vegetables. During inspection, be sure to check upper and lower leaf surfaces as well as the developing head. If you do notice any larva, hand pick and discard in a dish of soapy water.
Although obvious but not thought about as a preventative pest maintenance, is to look for any cabbage butterflies fluttering around your yard or near your vegetables.
Use lightweight row covers, cheesecloth, or nylon stocking stretched over a cabbage head to prevent butterflies from having access to your plants and lay eggs. Also, make sure to secure the material with stakes or weights to prevent it from blowing away.
Remove all weeds from your garden because they offer a convenient home for insect pests.
Destroy or plow under crop debris as soon as possible after harvest so that any larva remaining on plants will be destroyed as well as any overwintering pupae.
Finally, another organically acceptable method is the use of biological sprays such ad Bacillus thuringiensis and spinosad. They are safe to use and will not harm beneficial garden insets. Be sure to read and follow the manufacture instructions before use.
If you practice these organic methods of preventative insect pest maintenance, your vegetable garden will be well on its way to producing a healthy crop of vegetables.
I hope you enjoyed this article about the cabbageworm and found it informative.
More information on this pest can be found at wikipedia.org
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