Yellow Striped Armyworm: Essential Facts and Tips

The yellow-striped armyworm is a fascinating insect that you may have come across in your garden or on your farm. These creatures are often misunderstood, but knowing more about them can help you better manage their presence and protect your cherished plants.

One thing you should know is that these armyworms get their name from the distinctive yellow dorsolateral line that runs the length of their body source. They are known for their feeding habits and can be found on a variety of plants, causing damage to leaves and stems. Identifying and understanding their life cycle allows you to take preventive measures to protect your plants.

Moreover, the female moth of this species can lay up to 3,000 eggs, sometimes depositing as many as 500 in a single mass source. This makes controlling their population quite challenging, but learning about their behavior and natural predators can be useful in keeping their numbers under control.

Overview of Yellow Striped Armyworm

The Yellow Striped Armyworm (Spodoptera ornithogalli) is one of several species of armyworms that can affect various crops and plants. These armyworms are known for their distinctive yellow stripe along each side of their body. Western Yellow Striped Armyworm, a similar species, shares similar characteristics.

The larvae of Yellow Striped Armyworms have a unique appearance, varying from dark grey to black, with two bold yellow stripes along each side of their bodies. Moreover, you may find other less distinct stripes, like a pink stripe above their prolegs. As the larvae mature, they can grow up to 1½ inches long.

Adult Yellow Striped Armyworms have dark forewings with white and brown markings. The hind wings are pale but display a narrow dark line near the margin. With a wingspan that ranges up to 1½ inches, these moths lay up to 3,000 eggs, sometimes with as many as 500 eggs in a single mass.

Some of their notable features include:

  • Dark grey to black color with yellow stripes
  • An affinity for chewing on leaves from margins inward
  • Presence of multiple, less distinct stripes on the body

These armyworms commonly target crops such as peanuts, cotton, and soybeans. However, they also affect other plants, including those in the landscape. When dealing with Yellow Striped Armyworms, it’s essential to monitor for their distinctive markings and check crops regularly to mitigate potential damage.

Life Cycle and Development

Egg Stage

During the egg stage, female Yellow Striped Armyworm moths lay up to 3,000 eggs. They often deposit these eggs in clusters, with as many as 500 eggs in one mass.

Larval Stage

In the larval stage, Yellow Striped Armyworm caterpillars grow from about 2.0 to 35.0 mm in length over the course of development. These caterpillars have distinct coloration patterns:

  • Broad brownish band dorsally
  • Faint white line at the center
  • Two prominent yellow stripes along each side
  • A pink stripe above the prolegs

Pupal Stage

After completing their larval stage, the armyworm caterpillars tunnel into the soil and enter the pupal stage. At this stage, the pupae have a reddish-brown color and are about 5/8 inch long.

Adult Stage

Adult Yellow Striped Armyworm moths emerge from the pupae and have:

  • Wingspan up to 1½ inches
  • Dark forewings mottled with white and brown markings
  • Pale hind wings with a narrow dark line near the margin

Generations per Year

During the summer, a Yellow Striped Armyworm generation takes about 30 days to complete its life cycle. Droughty conditions can favor their development, leading to multiple generations in a year.

Physical Traits and Identification

In this section, we will discuss the physical characteristics of the yellow-striped armyworm to help you easily identify them.

Color and Markings

The yellow-striped armyworm is distinguishable by its unique color and markings. The body is predominantly black or dark brown and features two bright yellow stripes running along its sidewalls. In addition to these yellow stripes, there’s also a thin, dark line right between them. The contrast in colors makes them easier to spot in their natural habitats.

Size and Shape

When it comes to size and shape, yellow-striped armyworms are relatively distinct. Their size varies depending on their lifecycle stage, with fully grown larvae reaching up to 2 inches (5 cm) in length. The shape of these worms is somewhat cylindrical, and they tend to curl up when disturbed, further setting them apart from other worm species.

Habitat and Range

The Yellow Striped Armyworm, scientifically known as Spodoptera ornithogalli, can be found in various regions. It is a common pest with a broad geographical range.

In the United States, it is prevalent in the eastern part, extending west towards the Rocky Mountains. States like Florida are also affected by this pest. Beyond the US, its range extends up to southern Canada.

These armyworms are also native to other regions. They are present in Mexico, Central and South America, and many Caribbean islands. The Yellow Striped Armyworm can adapt to different environments, making it a widespread agricultural concern.

Populations tend to rise when conditions are favorable, such as during warm, humid weather. The larvae feed on various plants, often causing damage to crops. Being aware of their habitat and range can help you protect your plants and take necessary precautions to manage infestations.

Feeding and Damage

Food Plants

Yellow Striped Armyworms are known to feed on a variety of host plants. Here are some examples of their preferred food sources:

  • Vegetables: bean, corn, tomato, pea, cabbage, lettuce, watermelon, onion, asparagus, sweet potato
  • Field crops: cotton, wheat, alfalfa, soybean
  • Grasses: turfgrass

These pests are not very picky and can cause damage to many different plants, posing a significant threat to your garden or crops.

Damage Signs and Symptoms

To determine if your plants are under attack, you should look for specific signs of damage:

  • Feeding on leaves: Yellow Striped Armyworms usually start by feeding on the undersides of leaves, which can lead to the leaves appearing skeletonized.
  • Foliage damage: As they continue to feed, these worms may spread to other parts of the plant, often causing extensive damage to the foliage.

One crucial aspect of controlling and preventing armyworm damage is early detection. By regularly checking your plants, especially those listed as common host plants, you can catch these pests before they cause significant harm to your garden or crops.

Remember to be cautious and keep an eye out for any signs of Yellow Striped Armyworms in your plants. A friendly reminder: a little vigilance can go a long way in protecting your garden and crops from these destructive pests.

Impact on Agricultural Crops

Affect on Vegetables

Yellow Striped Armyworm can cause significant damage to various vegetables. These destructive pests are known to infest potatoes and cucumbers. For example, they may damage potato foliage and tunnel into cucumber fruits, causing significant crop loss. Their infestations can rapidly increase and result in considerable damage if not managed timely.

To prevent infestations, you should monitor your vegetable crops for signs of Yellow Striped Armyworm activity and implement proper pest management strategies.

Affect on Fruits

These pests can also attack fruit crops, particularly when close to infested field crops or vegetable gardens. Even though they are less common in fruit crops, it is important to be aware of their potential threats.

Remember to keep an eye on your fruit crops and apply the same preventive measures as for vegetables.

Affect on Field Crops

In field crops, Yellow Striped Armyworms can be quite destructive. They often migrate from one crop to another, causing widespread damage. Their voracious feeding habits can lead to significant yield losses if not controlled. Here are some key characteristics of Yellow Striped Armyworm infestations in field crops:

  • They prefer feeding on leaves, sometimes leaving large holes.
  • They can also cause severe damage to the stems and roots of field crops.

By staying vigilant and proactive in managing these pests, you can minimize the impact they have on your agricultural crops and maintain optimal yields.

Pest Management

Chemical Control

To treat yellow striped armyworm damage, you can use chemical insecticides such as bifenthrin, pyrethrin, and spinosad. However, some natural options are available like neem oil and Bacillus thuringiensis. Be sure to follow label instructions for the proper application rates and timing.

Pros:

  • Fast-acting
  • Effective in reducing armyworm populations

Cons:

  • May harm beneficial insects
  • Possible environmental and health concerns

Biological Control

Introducing beneficial insects like parasitic wasps and flies can help control armyworm caterpillars. Some examples of natural predators are:

These natural enemies can attack and kill armyworm larvae, reducing the need for chemical treatments.

Cultural Control

To prevent the spread of yellow striped armyworms, you can employ various cultural control methods:

  • Regularly inspect your plants for signs of damage or infestation.
  • Remove any dead or unhealthy plants to reduce hiding spots for armyworm caterpillars.
  • Encourage natural predators by providing them with shelters and suitable habitats.
  • Apply diatomaceous earth or soapy water on affected plants to deter the pests.

By combining chemical, biological, and cultural control methods, you can effectively manage yellow striped armyworm infestations in your garden or farm.

Interaction with Other Fauna

Yellow Striped Armyworms have various interactions with other fauna, including birds, insects, and moths.

The larvae are a food source for many birds, who help control their population by consuming them. On the other hand, armyworms have their share of competition with other insects. Both feed on similar plant foliage, leading to occasional encounters.

Moths play a crucial role in the life cycle of Yellow Striped Armyworms. Adult armyworms are moths themselves, with a wingspan of up to 1½ inches. They lay their eggs and when they hatch, larvae emerge, starting the cycle again.

To sum up the interactions:

  • Birds: Predators of armyworm larvae
  • Insects: Competitors for plant foliage as a food source
  • Moths: Adult life stage of Yellow Striped Armyworms

Remember, maintaining a balanced ecosystem is essential to prevent infestations of armyworms and other pests. By preserving habitats for natural predators like birds or creating garden spaces that attract beneficial insects, you can maintain an equilibrium in your outdoor environment.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Yellow-Striped Armyworm

 

Subject:  Caterpillar eating rhubarb
Geographic location of the bug:  Lancaster, PA
Date: 10/03/2021
Time: 10:06 PM EDT
Your letter to the bugman:  These caterpillars are devastating our rhubarb.    Any idea what they are?
How you want your letter signed:  Joe

Yellow-Striped Armyworm

Dear Joe,
This looks like a Yellow-Striped Armyworm,
Spodoptera ornithogalli, which is pictured on BugGuide.  The Yellow-Striped Armyworm is not listed on the Pacific Northwest Insect Management Handbook of rhubarb pests, but two other members of the genus are listed.  Armyworms and Cutworms are often general feeders and it is sometimes difficult to get a comprehensive listing of all the plants they will feed upon.

Authors

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  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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