Spodoptera exigua also known as the beet armyworms is a fearsome foe, capable of skeletonizing leaves, burrowing into plant crowns, and killing seedlings and young plants.
Beet armyworms are green caterpillars that eat a variety of ornamental and vegetable plants. The young larvae feed in groups and usually lack distinguishing markings that would allow them to be distinguished from other caterpillars.
Older larvae, on the other hand, develop a yellow stripe that runs from head to tail, making them easy to identify.
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Because older caterpillars are resistant to most insecticides, it is critical to detect and treat a beet armyworm infestation as soon as possible.
This article will help us identify a beet armyworm and how to prevent armyworms in the garden.
What Are Beet Armyworms?
Spodoptera exigua is a greyish-brown moth with a faint circular mark at the middle of the forewing.
The wingspan is about an inch or slightly longer. The back wings are whitish with dark edges. Caterpillars in the first and second stages are pale green with dark heads.
Older caterpillars are green to practically black with stripes down each side. A black spot on the side above the second pair of legs is always present in beet armyworms (counting from the head).
Initially, the pupa is smooth and light brown, but it quickly darkens. From pupae, a new generation of moths emerges. During its week-long life, each moth can lay up to 600 eggs, though some can live up to 30 days.
Some of their favourite vegetables include potatoes, beets, cauliflower, hydrangeas, corn, shallots, peas, bell pepper, tomatoes, and turnips. Weeds like lamb’s-quarter, mullein, creeping charlie, and purslane are also favourites.
Detecting Beet Armyworm Infestation
Beet armyworms eat irregular holes in the foliage, eventually skeletonizing it. They can devour sensitive young transplants to the ground and defoliate older plants. They dig into plants like lettuce and cabbage. Beet armyworms can also cause gouges in tender fruit, particularly tomatoes.
Armyworms can be prevented if they are discovered early. Look for millions of fluff-covered eggs, little caterpillars feeding in clusters, or a solitary giant caterpillar with a yellow stripe running down its side.
Life cycle
One generation can be completed in as little as 24 days, though 30 to 40 days is more typical. Pests at all stages of their life cycle can be found all year.
Each female lays 300 to 600 eggs in clusters of 50 to 150 on the undersides of leaves, near flowers, and on the tops of branches.
During periods of warm weather, the eggs hatch in two to three days and go through five, or sometimes more, instars. It takes two to three days to complete each instar stage.
They pupate about a half-inch deep in the soil, in chambers made of soil particles glued together by a sticky secretion that hardens when dry.
Methods of Control
It’s preferable to use a combination of control strategies as part of an integrated pest management (IPM) approach to lower their populations for the safest, most effective control.
These approaches range from handpicking larvae to employing live natural enemies to hunt bugs for you.
1. Use Of Organic Pesticides
When it comes to pesticides, whether organic or chemical, timing is everything. Most products are only effective when applied before the larvae reach half an inch in length.
Thorough coverage is also essential, whether of the leaves the larvae are eating or of the insects themselves.
To combat the larvae, neem oil can be used. Bonide sells it in ready-to-use gallon and quart bottles.
The larvae are vulnerable to a kind of beneficial bacterium known as Bacillus thuringiensis v. Aizawa, or Bta, which is sold at Arbico Organics under the brand name Agree WG.
Bta works best on very young larvae, therefore attentive monitoring to locate the larvae before they get too big will pay off!
Spinosad also works well against a variety of pests, including armyworms.
Bonide Insecticidal Super Soap, available at Arbico Organics, combines the benefits and effects of Spinosad and insecticidal soap and is suitable for use on both food and ornamental plants.
2. Control, Both Cultural And Physical
Because these insects prefer certain types of weeds, seek to eradicate them if they are growing near your garden to limit spread from the margins to your plants.
Throughout the season, scout the veggie patch frequently and destroy affected foliage or handpick and destroy eggs and larvae as you find them.
After harvesting, cultivate the plot to expose and kill any prepupae and pupae that may have developed in the soil.
Exclusion tactics and materials, such as floating row covers, can be used to protect your plants from moths that want to lay eggs on them.
3. Biological Management
Biological control options include attracting or purchasing natural biological enemies and applying them to help keep pest populations in check.
It can be effective enough to keep levels below the action thresholds for using chemical treatments, but the mortality rate achieved by each natural enemy varies depending on geographical region and crop type.
This pest’s eggs and small larvae are not safe in the wild. Miniature pirate bugs, big-eyed bugs, damselflies, and predatory stink bugs are all on the lookout for these delectable morsels.
There are also several fungal infections, such as Erynia and Metarhizium rileyi (syn. Nomurea rileyi), that will kill off some of the larvae before they become an issue for you.
The red imported fire ant, Solenopsis invicta, will also attack the pupae, but it is a major problem in its own right. Beneficial nematodes are a superior alternative for pupae control.
Nematodes of the genera Steinonerma and Heterorhabditis will infect beet armyworms in their prepupal and pupal stages in the soil.
- Pesticides Containing Chemicals
Pesticide-resistant pests are a major issue for gardeners and farmers alike, and the beet armyworm is no exception.
Chemicals are routinely and abundantly sprayed on the leaves of sensitive crops to prevent and control beet armyworm infestations, which promotes resistance development.
Final thoughts
With a penchant for practically any crop, you could wish to plant in your garden, an insect-like beet armyworm poses a formidable foe.
Add in a few aggravating elements, like pesticide resistance, and these voracious bugs can appear unstoppable.
Fortunately, there are a few solutions accessible, including cultural, physical, biological, and, if required, chemical ways of control.
Have you ever seen these voracious larvae chewing their way through your plants? Which vegetable did they appear to favour, and how did you deal with them? Please share your thoughts in the comments section below!
