Protect Your Lawn This Season: A Complete Guide to Identifying and Managing Fall Armyworms

Protect Your Lawn This Season: A Complete Guide to Identifying and Managing Fall Armyworms

Is your lawn looking less vibrant or showing unexplained patches of damage? Fall armyworms could be the cause. These pests are notorious for their rapid destruction of grass and crops, especially during the warmer months. This comprehensive guide will help you identify fall armyworms, understand their life cycle, recognize the damage they cause, and learn effective strategies to control them.
Protect Your Lawn This Season: A Complete Guide to Identifying and Managing Fall Armyworms 1

What Are Fall Armyworms?

Appearance:
  • Size: Approximately 1 to 1.5 inches long.
  • Color: Varies from green to mottled brown or almost black.
  • Distinctive Markings:
    • 1. A wide, dark stripe on each side of the body.
    • 2. Four black dots arranged in a square on the back of each abdominal segment.
    • 3. An upside-down, light-colored "Y" marking on the head capsule.
Life Cycle:
  • 1. Eggs: Laid in clusters on grasses or flat surfaces like fences and buildings. A single female moth can lay up to 1,000 eggs, which hatch within 2 to 10 days.
  • 2. Larvae (Caterpillars): After hatching, larvae feed on grass blades for 2 to 3 weeks.
  • 3. Pupae: Larvae burrow into the soil to pupate, forming reddish-brown capsules.
  • 4. Adults (Moths): Emerge with a wingspan of about 1 to 1.5 inches and have a noticeable white spot near the center of each forewing.

Source: NC Turf Bugs

Why Are They a Problem?

Fall armyworms have a voracious appetite and can cause significant damage in a short period. They prefer grasses but have a wide host range, including crops and ornamental plants. In large numbers, they can strip a lawn bare, moving in groups (hence the name “armyworm”) and leaving a clear line between damaged and undamaged areas.
Protect Your Lawn This Season: A Complete Guide to Identifying and Managing Fall Armyworms 2

How to Identify a Fall Armyworm Infestation

1. Inspect Your Lawn
  • Look for Activity: Early morning or late afternoon are the best times to spot them, as they avoid the midday heat.
  • Soapy Water Test: Mix a few drops of dish soap with water and pour it over a small patch of grass. This irritates the caterpillars, causing them to surface.
2. Confirm It’s Fall Armyworms
  • Check for the Upside-Down "Y": Examine the head of any caterpillars you find for the distinctive marking.
  • Observe Body Markings: Look for the dark stripes and square sets of black dots along their bodies.
  • Exclude Other Pests: If these features aren't present, you may be dealing with a different pest.

Source: TurfFiles - Fall Armyworm in Turf

Assessing the Infestation

Determine the Life Stage Present
  • Cut a Small Turf Section: Examine the top two inches of soil.
  • Identify Pupae and Larvae:
    • 1. Pupae: Reddish-brown capsules about an inch long.
    • 2. Larvae: Active caterpillars feeding on grass roots and blades.
  • Action Based on Findings:
    • 1. More Pupae: Indicates larvae have matured.
      • Immediate Action: Apply a diamide insecticide now or a pyrethroid insecticide in 3 to 5 weeks to target emerging moths.
    • 2. More Larvae: Active feeding stage; proceed to measure caterpillar size.
Measure the Caterpillars
  • Size Matters:
    • 1. Less Than 1 Inch: Early stages.
      • Quick Control: Use a pyrethroid insecticide for immediate but short-term control (1–2 weeks).
      • Long-Term Protection: Apply a diamide insecticide for extended protection, though it may take a few days to become effective.
    • 2. Greater Than 1 Inch: Late stages nearing pupation.
      • Immediate Treatment: Apply a diamide insecticide now.
      • Alternative: Use a pyrethroid insecticide in 3 to 5 weeks to target the next generation.

Source: NC Turf Bugs

Recognizing the Damage

  • Pattern of Damage:
    • 1. Sudden Brown Patches: Areas where grass appears chewed or thinned out.
    • 2. Distinct Lines: A clear demarcation between damaged and healthy grass as armyworms move en masse.
  • High-Risk Areas:
    • 1. Near Structures: Infestations often start near fences, signs, or buildings where eggs are laid.
    • 2. New Sod: Newly installed grass is more attractive and susceptible to armyworms.

Source: TurfFiles - Fall Armyworm in Turf

Effective Control Methods

Biological Control
  • Natural Predators: Encourage beneficial insects like lady beetles, which feed on fall armyworm eggs and small larvae.
  • Healthy Ecosystem: Maintain biodiversity in your lawn to support predator populations.
Chemical Control
  • Use Liquid Insecticides: More effective against fall armyworms compared to granular forms.
  • Insecticide Options:
    • 1. Pyrethroids (e.g., lambda-cyhalothrin):
      • Best For: Quick knockdown of small larvae.
      • Duration: Short-term control.
    • 2. Carbamates (e.g., carbaryl):
      • Effective Against: Younger larvae.
    • 3. Diamides (e.g., chlorantraniliprole):
      • Best For: Early application for long-lasting protection.
      • Duration: Several weeks.
  • Application Tips:
    • 1. Preparation: Mow the lawn and lightly water before treatment to encourage larvae to the surface.
    • 2. Timing: Apply treatments in the early morning or late evening when larvae are active.
    • 3. Follow Label Instructions: Always read and adhere to the product's directions for safe use.

Source: TurfFiles - Fall Armyworm in Turf

Preventive Measures

  • Regular Monitoring: Inspect your lawn weekly during peak seasons (late summer to early fall).
  • Healthy Lawn Practices:
    • 1. Proper Mowing: Keep grass at recommended heights.
    • 2. Adequate Watering: Maintain proper irrigation to keep grass healthy and less susceptible.
  • Avoid Over-Fertilizing: Excessive nitrogen can make your lawn more attractive to pests.

When to Seek Professional Help

If the infestation is severe or you’re unsure about treatment options:
  • Consult Experts: Reach out to lawn care professionals for assessment and treatment.
  • Local Extension Services: Contact your local cooperative extension for region-specific advice and recommendations.

Frequently Asked Questions

  • Q: Can fall armyworms harm humans or pets?
  • A: No, fall armyworms do not pose a threat to humans or pets. They are strictly plant feeders.
  • Q: Will my grass recover after an armyworm infestation?
  • A: Healthy lawns can often recover with proper care. Reseeding or resodding may be necessary in severe cases.
  • Q: How can I prevent future infestations?
  • A: Regular monitoring and maintaining a healthy lawn are key. Applying preventive treatments during peak seasons can also help.
By staying vigilant and taking prompt action, you can protect your lawn from fall armyworm damage. Remember, correct identification and timely treatment are crucial in managing these pests effectively. If you need further assistance or professional treatment options, our team is here to help you maintain a healthy, beautiful lawn all season long.
Sources: