Controlling Fall Armyworms On Turf

How to Control Fall Armyworms on Turf


Controlling Fall Armyworms On Turf

During the fall months fall, armyworms can become a real threat to lawn turf, this has caused growers and turf managers to put programs in place to bring control because of the destruction fall armyworms cause. Fall armyworms are a serious threat because as the name depicts they travel in small armies consuming just about everything in their path. If you’re not sure what to look for or if you suspect that your turf may be affected by these worms this guide can help you to identify and bring control to this lawn turf pests issue. Continue reading to win the war on fall armyworms

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Fall Armyworm Biology

Fall armyworms usually occur in the late summer or early fall, the adult moth is ash-gray in color with a wingspan that ranges about 1 1/2″ inches. The front wings are smaller with a mottled gray and brown color, and the back wings are large and white in color and have narrow edges that are smoky brown. Moths become active just as nighttime arrives.

During the night hours, the female moth lays or distributes her eggs in masses up to several hundreds on surfaces that are light in color, The eggs are covered in fuzz from the female’s body that’s geryish in color the eggs however are grey. As the masses age, they get darker, the eggs hatch in about 2 to 4 days.

Once the eggs hatch tiny blackhead larvae with a light color begin to emerge and then use silken webs to spin down or make contact with the turf, their body will darken as the larvae mature. Stripes that are noticeable also appear, larvae that are fully mature are  11⁄4ʺ to 11⁄2ʺ   long and have various colors from light green to somewhat blackish with several stripes along their bodies. The moths of the fall armyworms live for about 10 days.

From egg to fully mature larvae takes anywhere from 2 to 3 weeks. The larvae will burrow into the soil and form pupae, and in about 10 to 14 days moths will begin to emerge. What’s interesting to note is there may be four or more generations per year because development can take about 2 to 4 weeks,

Note: The fall armyworms are among the largest larvae found in turfgrass, fall armyworms are easier to spot from webworms because of their large stripped bodies. Four spots can be seen on their segmented body. Each spot on the posterior segment is arranged in a square shape.

Damage of Fall Armyworms

Fall armyworms are most active during the early morning or late afternoon and early evening hours, but may also be found feeding during the day hours. They may be seen in large numbers marching across lawns. The damage of these worms is caused by chewing the plant’s tissue and feeding on unmowed turf that’s tall or overgrown, these pests consume a variety of plants.

Turf grass are included for example bluegrass, fescue, bentgrass, and ryegrass but their favorite is bermudagrasses that’s maintained and fertilized, the damage However may vary in appearance and severity according to the turf type and how turfgrass is maintained. These armyworms feed on a host of different plant species but prefer grasses and corn. Armyworms will feed on most warm and cool season turfgrass.

How to Manage Fall Armyworms

There are many predators of the fall armyworms for example birds, beetles, rodents, wasps, earwigs, etc… their presence on your turfgrass may be an indication that you have a fall armyworm infestation. If there are flocks of birds consistently feeding in turf grass areas may be an indication of fall armyworms. There may also be small holes as signs of where birds were feeding.

Signs that armyworms are present are, typically areas that are damaged will start around where the masses of eggs have been laid and spread outwards, the damage of fall armyworms often appears as brown or burned patches that have the appearance of a lawn that’s drought stress. If your turfgrass shows signs of stress inspect immediately.

For further testing flush the area with soapy water, the soapy water can be applied to or over a 1-to-2 square-foot area, if the armyworm larvae are present will cause them to surface or come to the top. To make a soap flush mix 2 tablespoons of dish liquid soap with 1 gallon of water, shake the mixture thoroughly to combine, next fill a watering can or jug with the soapy water, and apply as was discussed.

What I love about the use of soapy water is this method may also bring mole crickets, sod webworms, and other armyworms to the surface if they are present.

Insecticides for Fall Armyworms Control

Fall Armyworms Control Product Names

1. Bayer Advance 24 Hour Grub Killer PlusGranular formulation.

2. Ortho Bug-B-Gone Insect Killer-Granular and spray (RTU and concentrate) formulations.

3. Thuricide-Spray- (RTU and concentrate).

4. Bioadvanced Complete Insect KillerGranaular and spray  (RTU) formulations.

5. Hi-Yield Turf 38 Plus Turf, Termite and OrnamentalGranaular and Spray (RTU and concentrate) formulations.

6. Spectracide Triazicide Insect KillerGranular and spray formulation  (RTU and concentrate ) formulations.

Fall Armyworms Application Methods

Insecticide Application Tips

  • Time of Day: Treat the lawn during the early morning or the late afternoon hours, when the caterpillars are most active, on grass turf that’s thick and established. Apply spray, 1 gallon per 1,000 square feet. When applying spray stop irrigation for at least 24 hours.
  • Lawn Care Method: If mowing is needed mow before treatment application early or late in the day. Mowing will remove portions of the grass blades reducing the depth of the turf the insecticides need to penetrate. Deciding to mow after application treatments can also cause the granular to be removed or carried away as grass clippings are caught in the lawnmower bag
  • The Label is the Law: Following the manufacturer’s direction is so important for the best results so before applying treatment read and follow the instructions
  • Repeat Application as Needed: One application may not be enough, inspect if fall armyworms are eliminated or if they are still present after seven days. If more armyworms are present then treat the turf lawn again. According to the severity of the infestation, you may have to treat it multiple times

Recovering Your Lawn from Fall Armyworm Damage

  • Once your lawn has been treated and there are clear signs that  fall armyworms are brought under control ensure that your lawn is adequately watered to encourage new growth
  • Applying a turf builder such as  Scotts® Turf Builder Triple Action, will help to promote growth and strengthen your turfgrass, If fertilizer application was done before infestation then wait for a least a month before another fertilizer application
  • Warm-season grass types are hardier and may need fertilizer applications to recover but Northen lawns may need a little help, overseeding your lawn will produce a thick lush healthy growth.  Scotts® Turf Builder® Thick’R Lawn™ Sun & Shade will get the job done for you.

Additional Information

  • Fall armyworms appear typically in Northern Georgia from July until the first frost
  • Ensure that your lawn gets inspected each day from July through the first frost for fall armyworm activity
  • Learn the biology of fall armyworms for proper control
  • If fall armyworm activity is discovered early and treated correctly damaged turf can recover quickly
  • Fall armyworms are attracted to lawns that are newly installed because new lawns are watered and fertilized
  • Control chemicals for the control of fall armyworms in lawns are not often labeled for fall armyworms but are labeled for caterpillar pests for grass turf

The final word on controlling fall armyworms on turf

Fall armyworms are a serious pest and can cause a beautiful lawn to be reduced to a nightmare, the good news is this guide can help you to detect early signs and apply the right treatments so that your lawn can recover. If you are having issues with this turf pest we are here to help you, why let these worms reduce the beauty of your lawn? with this guide, you can win the war on fall armyworms.


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About the author

+ posts

Norman loves being in the garden, both at home and for his job....
he is 'Natures Little helper' being outdoors, growing his vegetables and flowers from an early age.
Now having spent over 22 years in the profession he want to give some of his knowledge to others...
his vast array of hints and tips you will find scattered over this site will help you no end growing plants in your garden.

2 thoughts on “Controlling Fall Armyworms On Turf”

  1. Fall armyworms can indeed wreak havoc on lawns, and it’s essential for homeowners and turf managers to be equipped with knowledge on how to identify, manage, and ultimately overcome this pest issue. To that point, could you share a photo (or link) of what they physically look like? The detailed explanations are helpful, but a photo would remove any doubt about what I’m looking for. 

    The descriptions of fall armyworm biology, signs of damage, and various control methods are incredibly valuable, so just hoping to learn more. Thanks for the recommendations for specific products and the emphasis on following manufacturer instructions for effective control!

    • These worms can do such damage to lawn turf grass, this guide will help you to have much success. I will see if I can get a photo to you. All the best and have a good day!!


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