Are Yellow Striped Armyworm Poisonous? Debunking Myths and Facts

Yellow striped armyworms, scientifically known as Spodoptera ornithogalli, are often seen feasting on various plants, their preferred hosts being tomatoes, beans, and alfalfa.

These pests may cause considerable damage to crops, leading many to wonder if they are poisonous to humans or other animals.

Are Yellow Striped Armyworm Poisonous
Yellow-Striped Armyworm

Are Yellow Striped Armyworm Poisonous?

While the western yellow-striped armyworm can be destructive to plants, there is no evidence suggesting that they are poisonous to people or animals.

These larvae feed mostly on foliage, but they are not known to pose any significant health threats beyond being agricultural pests.

Yellow Striped Armyworm: Overview

Identification

The yellow striped armyworm, also known as Spodoptera ornithogalli, is a type of caterpillar.

These caterpillars are usually black or green with distinct yellow stripes on their sides.

They belong to the species of armyworms and their appearance helps with identifying them correctly.

Life Cycle

Yellow striped armyworms have a typical life cycle of a moth:

  • Eggs: Females can lay up to 3,000 eggs, with as many as 500 eggs in one mass^[4^].
  • Larvae: The caterpillar stage, during which they display their characteristic yellow stripes.
  • Pupa: The transformation phase, with reddish-brown pupae measuring approximately 5/8 inch in length^[4^].
  • Adult: The moths have dark forewings mottled with white and brown markings, and their hind wings are pale with a narrow dark line near the margin. Wingspans can reach up to 1½ inches^[4^].

Habitat and Distribution

Yellow striped armyworms are common pests for various crops such as greens, tomatoes, peppers, beans, cucurbits, and cole crops.

They primarily feed on foliage in the early season and can cause serious damage to young plants.

In later seasons, they also feed on other parts of the plants, affecting crops such as tobacco, soybeans, corn, and alfalfa.

File:Yellow-striped Armyworm and eggs - Spodoptera ornithogalli, Julie Metz Wetlands, Woodbridge, Virginia.jpg
Source: Judy GallagherCC BY 2.0, via Wikimedia Commons

These armyworms can be found in different parts of the United States, including Kentucky, Florida, and Oklahoma, where they can cause damage to peanuts, cotton, and soybeans, among other crops.

Here is a comparison table highlighting the features of yellow striped armyworms:

FeatureYellow Striped Armyworm
Scientific NameSpodoptera ornithogalli
ColorBlack or green with yellow stripes
HabitatVarious crops and agricultural areas
DistributionThroughout the United States
DamageFoliage feeding and crop destruction

Pros of yellow striped armyworm identification:

  • Helps farmers and gardeners identify and manage pests effectively
  • Awareness of their presence can lead to early intervention and lesser crop damage

Cons of yellow striped armyworm identification:

  • Timely identification can be challenging, leading to substantial crop loss
  • They can spread to other crops or fields if not managed effectively

Potential Harm and Risks to Crops

Signs of an Infestation

Yellow-striped armyworms are known to attack a variety of crops, including vegetable crops like tomatoes, beans, cabbage, cucumber, and potatoes, as well as other crops such as corn, alfalfa, and tobacco.

Signs of an infestation include:

  • Holes or chewed marks on leaves and foliage
  • Presence of armyworm caterpillars on plants
  • Damage to new growth and young plants

Damage Caused to Plants

These pests can cause significant damage to crops in a short amount of time by feeding on foliage. For some crops, the damage can be more severe:

  • Tomatoes: They may feed on both leaves and fruit, potentially causing complete defoliation.
  • Beans: The armyworms can consume entire leaves, leaving only the veins and stems behind.
  • Alfalfa: They can severely affect yield and quality by feeding on leaves and stems, as well as potentially reducing the regrowth of cut alfalfa plants.

In addition to vegetable crops, yellow-striped armyworms also attack turfgrass1, posing a risk to lawns and parks, and tobacco2, damaging its leaves.

Comparison Table: Damage caused by Armyworms

CropDamageSeverity
TomatoLeaf and fruit consumption, defoliationHigh
BeansEntire leaves eaten, leaving veinsModerate
AlfalfaLeaf and stem consumption, reduced yieldModerate
TurfgrassLoss of leaf tissueModerate
TobaccoDamage to leavesModerate

Despite the potential harm and risks posed by yellow-striped armyworms, it is important to note that these pests are not poisonous or harmful to humans.

Source: Image via Flickr by John Brandauer 

Armyworm Control and Management Strategies

Monitoring and Early Detection

  • Regularly inspect crops for signs of yellow-striped armyworms.
  • Look for chewed leaves and small larvae.

Monitoring and early detection are crucial to controlling yellow-striped armyworm.

Check young plants and transplanted crops frequently, as smaller larvae are easier to control than larger stages1.

Early detection helps in applying timely and effective control measures.

Beneficial Insects and Natural Enemies

  • Natural predators: birds, predatory beetles, and parasitic wasps.
  • Examples: tachinid flies, braconid wasps, and lady beetles.

Beneficial insects and natural enemies can help keep armyworm populations in check2.

Encourage their presence by providing habitats and avoiding broad-spectrum insecticides.

Cultural and Physical Control Strategies

  • Till soil to expose pupae to predators and unfavorable conditions.
  • Use crop rotation to reduce the likelihood of infestations.
  • Handpick larvae or wash them off with soapy water.

Cultural and physical control strategies interfere with the armyworms’ life cycle, making it difficult for them to thrive3.

These methods are environmentally friendly and reduce the need for chemical controls.

Chemical Control Options

ChemicalProsCons
Bacillus thuringiensis (Bt)Effective on small larvae; safe for beneficial insects4Less effective on larger larvae
SpinosadEffective on multiple pests; low toxicity5May harm some beneficial insects
Neem oilNatural substance; lower toxicity6Limited residual activity; may need multiple applications

Chemical control options are available for yellow-striped armyworm.

Choose products that will not harm beneficial insects and have minimal environmental impact. Always follow label instructions for proper use.

Yellow Striped Armyworm

Armyworm Life Stages

Eggs

Yellow-striped armyworm eggs are laid in clusters on leaves or stems.

Females can lay up to 3,000 eggs, with as many as 500 eggs in one mass. Some key features of armyworm eggs include:

  • Clustered on leaves or stems
  • Multiple broods per year

Larvae

Armyworm larvae are the most destructive stage in the life cycle, feeding on leaves, fruit, and other plant parts.

Yellow-striped armyworm larvae can be identified by:

  • Varied coloration, from pale green to black
  • Prominent yellow stripes on each side
  • Develop through multiple instars

The larvae feed on a variety of plants, but they have a preference for fruit and other food crops.

Pupae

Yellow-striped armyworm pupae are reddish-brown, about 5/8 inch long, cylindrical, and slightly pointed at the rear.

Pupation occurs in the soil, and this stage is crucial for the development of adult armyworms.

Adult Moths

Adult moths of yellow-striped armyworms have dark forewings mottled with white and brown markings.

Their hind wings are pale with a narrow dark line near the margin. These moths have a wingspan of up to 1½ inches.

The adult stage is responsible for the spread of the species as they can fly long distances to lay eggs in new areas.

Adult armyworms are mainly focused on reproduction, not feeding.

Armyworm StagesCharacteristicsImportance in Life Cycle
EggsClustered, laid on leaves or stemsInitiate infestation
LarvaeVaried coloration, yellow stripes, multiple instarsFeed on plants, cause damage
PupaeReddish-brown, 5/8 inch long, in soilTransition stage, develop into adults
Adult MothsMottled wings, 1½ inch wingspan, fly long distancesLay eggs, spread to new locations

Comparing Yellow Striped Armyworms to Other Armyworm Species

Beet Armyworm

The Beet Armyworm (Spodoptera exigua) is known for attacking various crops, such as tobacco and vegetables.

This species is different from the Yellow-striped Armyworm (Spodoptera ornithogalli) in size and color patterns:

  • Size: Beet Armyworms are smaller, with mature larva reaching 1 to 1.5 inches.
  • Color: They have a green body with a white, wavy stripe along both sides.

The larval stage of both species is the most destructive, causing defoliation and damage to crops. However, neither is known to be poisonous to humans.

Fall Armyworm

Fall Armyworms (Spodoptera frugiperda) are larger than both the Yellow-striped Armyworm and Beet Armyworm. Some distinguishing features include:

  • Prolegs: Fall Armyworms have four pairs of prolegs, compared to five in Yellow-striped and Beet Armyworms.
  • Instar Stages: Fall Armyworms typically have six instar stages, while Yellow-striped and Beet Armyworms usually have five.
  • Pupae: Fall Armyworm pupae are reddish-brown, differentiating them from the dark brown pupae of other armyworm species.

Despite their differences, all three species share the trait of being harmless to humans, as they do not produce toxins or cause direct harm.

Yellow Striped Armyworm

SpeciesSizeColor PatternsProlegsInstar StagesPupae Color
Yellow-striped1.5-2 inchesAlmost black with yellow stripes on sides55Dark brown
Beet Armyworm1-1.5 inchesGreen with white, wavy stripes on sides55Dark brown
Fall ArmywormLargerVaries; often brown or green with stripes46Reddish-brown

Geographic Range and Seasonality

North and Central America

The yellow striped armyworm (Spodoptera ornithogalli) can be found in North and Central America, with activity in the United States typically occurring from March to November.

In California, for example, they may be most active between June and August, feeding on various crops such as cantaloupe, lettuce, cabbage, cucumber, potato, and watermelon.

  • California activity: June to August
  • Main crops affected: cantaloupe, lettuce, cabbage, cucumber, potato, watermelon

In Mexico and other parts of Central America, yellow striped armyworms have similar feeding habits, impacting vegetable crops and fruit trees during their larval stage.

Caribbean and South America

Further south, in the Caribbean and South America, these armyworm caterpillars also cause damage to a variety of crops.

Turfgrass and tobacco are among the affected plants in these regions. The yellow striped armyworms can spread throughout these areas, with generations occurring from March to November.

In comparison to other species of armyworms, the yellow striped armyworm is identifiable by its distinct yellow stripes and a dark spot on the side of its body.

These armyworm caterpillars can be controlled by beneficial insects during their instar stages.

Key Characteristics

  • Yellow stripes
  • Dark spot on the side
  • Multiple generations (March-November)

Pros and Cons of Yellow Striped Armyworms

Pros:

  • Provide food source for beneficial insects

Cons:

  • Cause damage to various crops
  • Spread rapidly across regions
Species of ArmywormsAffected RegionsFeeding Habits
Yellow StripedNorth America, Central America, Caribbean, South AmericaCantaloupe, lettuce, cabbage, cucumber, potato, watermelon, turfgrass, tobacco

Yellow Striped Armyworm

References and Resources

Yellow striped armyworms are a common pest affecting various crops, such as vegetables, soybeans, beans, and tobacco.

They can be particularly damaging in Kentucky. To better understand their impact and control methods, below are some helpful resources.

Harmful Effects

  • Damage inflicted on young plants due to foliage feeding
  • Feeding on the underside of leaves causes skeletonization

Natural Enemies

Yellow striped armyworms have known natural enemies that help control their population:

  • Parasitic wasps
  • Flies
  • Nuclear polyhedrosis virus

These enemies can be valuable allies in a vegetable garden.

Habitat Range

Comparison of yellow-striped armyworm species’ habitat range:

SpeciesHabitat
Spodoptera ornithogalliEastern United States, including Kentucky
Spodoptera praeficaWestern United States, particularly in the Rocky Mountains region

Appearance

  • Larvae appear pale green or grey with yellow stripes
  • Adults are reddish-brown in color with a wingspan of 38mm

By being aware of yellow-striped armyworms’ presence, understanding their characteristics, and utilizing their natural enemies, you can successfully manage their impact on your crops.

Conclusion

So, to wrap things up, yellow-striped armyworms aren’t harmful to humans directly.

They might damage plants, and their tiny hairs could make skin itchy.

But they’re not poisonous, so they’re not dangerous to people.

Remember to be careful around them to avoid any discomfort, and know that they’re just a part of nature doing their thing.

Footnotes

  1. True armyworm larvae in Turfgrass  2
  2. Yellow-striped armyworm in Tobacco  2
  3. https://extension.umn.edu/corn-pest-management/armyworm 
  4. https://content.ces.ncsu.edu/yellowstriped-armyworm 
  5. https://www.ndsu.edu/agriculture/ag-hub/publications/armyworm-and-army-cutworm 
  6. https://www.gardeningknowhow.com/plant-problems/pests/insects/armyworm-control.htm 

Reader Emails

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

Letter 1 – Yellow Striped Armyworm

Subject: Caterpillar ID
Location: Kingsland, TX
October 1, 2016 4:44 pm
Found several of these on my pride of Barbados. Curious as to what they are and if I can move them before they devour the whole thing.
Signature: Lindsay C

Yellow Striped Armyworm
Yellow Striped Armyworm

Dear Lindsay,
We found an image matching your image on the University of Maryland extension website, and it is identified as a Yellow Cutworm.  When we checked BugGuide, we found an image of the Yellow Striped Armyworm,
Spodoptera ornithogalli, and it appears to be a match to your individual. 

According to BugGuide:  “Larvae feed on many herbaceous plants, including alfalfa, asparagus, bean, beet, cabbage, clover, corn, cotton, cucumber, grape, grass, jimsonweed, morning glory, onion, pea, peach, peanut, pokeweed, sweet potato, tobacco, tomato, turnip, wheat, watermelon, and wild onion.”  You can read more about the Yellow Striped Armyworm on Featured Creatures.

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    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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