If you live in the Southeast (even as far north as North Carolina and north Georgia) and love your lawn, please scout for fall armyworms (FAW) daily.
Fall armyworms are not indigenous to our area and cannot overwinter here. They are the larval of a subtropical moth that migrate up here from the gulf coast and tropics. Their arrival is usually around midsummer, so be on alert for FAW activity every year from July until first frost.
"Armyworms" get their name from their behavior of moving across lawns in an army-like fashion; they aren't really worms at all - they're caterpillars. We'll explain everything you need to know about FAW in this blog, including how to get rid of them.
Fall Armyworms in New Sod
Fall armyworms love new sod above everything else, but they will eat established sod too.
Their culinary propensity for new sod makes it appear that these creatures arrived with new sod, but lawn care experts and extension specialists are familiar with this problem and know that FAW are already on site before new sod is laid.
New sod is like a fresh buffet spread out before them.
NC State University writes about FAW damage in new sod. See fourth paragraph under "Damage."
Fall Armyworm life cycle - Explained
Insect life cycles involve a lot of metamorphosis. This is what it looks like to be a fall armyworm:
eggs > larvae > pupae > moths
Eggs are laid in shrubs adjacent to turf or in unexpected places like sides of building, fences, posts, signs, old cars, and I've even seen a picture of their egg masses on a flag. They are found in unlikely, inhospitable places such as on a black post, as shown in the picture.
We rarely see them in our production fields because with hundreds of acres of tightly mowed turf there is nowhere suitable for them to lay their eggs.
FAW Larvae /Caterpillars - The Damaging Phase
When eggs hatch, out comes the larvae that goes hog wild on your lawn. The "larvae" are really the "worms" which are really "caterpillars."
These caterpillars are the damaging phase.
Fall armyworm pupa (top) and larva (bottom).
Cutworm (big one on the left) for comparison with a fall armyworm (small one on the right).
FAW can be identified by the upside down V on their heads and the alternating bands along the body.
The larvae become the pupae, which are non-damaging, but they are ugly, cockroach-colored things that bury themselves into the soil.
The pupae "pupate" into moths, which are considered the adults, and it's the moths/adults that have the babies. The moths lay a new round of eggs and the cycle repeats itself. Sooooo, if you've had fall armyworms once, look for them twice. We hate it too.
How do I know if I have fall armyworms?
- If your sod has become discolored or looks like it has been exposed to frost, you possibly have them. The damage often begins on the edge of the lawn and moves across.
- A large number of birds in a turf area may be a sign of armyworms since they are an excellent food source for birds.
- Notice how you don't see them everywhere at once on your lawn. They march across from one side of the lawn to another because they hatch from eggs that were deposited adjacent to the lawn. If the FAW came with the sod, they would be everywhere at once eating sod.
- Test for armyworms with a soap flush that brings them to the surface so you can see them. We've explained the flush test here: Soap Flush Test for Pests
FAW damage across a Tall Fescue lawn, a favorite of fall armyworms.
Treating Fall Armyworms
There is no "over the counter" preventative treatment available to homeowners for FAW in the egg, pupa, or moth stages.
However, insecticide is available to homeowners for treating when they're in the larva/caterpillar stage, which is when they are doing their damage.
- There are an abundance of insecticides available on the market that treat armyworm infestations. Many of our stores carry products (please call ahead to confirm we have them in stock.)
- Liquid insecticides are best if you are combatting an infestation. We recommend two treatments: one in the evening and one the next morning
- If you're laying new sod, we have a fertilizer/insecticide combo we recommend. It's 5-10-30 with Acelepryn systemic insecticide to give preventative control for fall armyworms in the larva/caterpillar stage.
- Repetition: Treat more than once. Just because the armyworms have gone to pupae stage does not mean they are gone. They will mature, lay eggs, hatch, and infest your yard again. Be vigilant and treat multiple times according to the insecticide instructions in order to break the armyworm life cycle.
- Time of Day: Early morning or late afternoon is the best time because the armyworms are active. If applied mid-day and the armyworms may be below the surface of the new turf and the application will not be as effective.
- Act Immediately: When you see a sign of them, treat your lawn immediately because they can do terrible damage within 24 hours.
- Stock Up: If you live in an area prone to infestation, stock up on insecticide and be prepared to defend your yard with treatment when necessary.
- Read the Label: Make sure to read all insecticide instructions carefully and apply at the application rate recommended on the product label for the pest you are targeting.
It's always sad when a customer calls about FAW. Here's a picture of a beautiful lawn that was attached by FAW three weeks after being installed. The new sod is the brown section; the green section was laid two month earlier. The FAW troops attacked the new sod first, from the perimeter, moving inwards.
Our Stores carry FAW insecticide, but if you don't live near us please contact your local garden center. In the case of the customer's lawn above, Scott at our Gwinnett, GA store told me, "We spoke on the phone at about 4:20pm one afternoon [we close at 5:00pm], so I told him to run to someplace that's open this evening. It made more sense to get them treated immediately than to wait until we opened the next day."
When the Battle with Fall Armyworms is Over
The good news is that, in most cases, a warm season type of lawn will recover. FAW don't eat stolons and rhizomes of warm season turf and growth will resume from those resilient plant parts.
Steps to Help Your Lawn Recover from FAW Damage
- After you've applied your insecticide treatments, we recommend applying starter fertilizer (5-10-30) (without Acelepryn) to your lawn ASAP to give it a boost in regrowing.
- Continue to water your lawn each morning for several days, also to boost regrowth.
While warm season grasses, given proper care, will typically recover from FAW damage, damage to tall fescue is often much more significant.
Tall Fescue simply does not have the same tolerance to FAW activity, particularly if it is not very well established. As a result, FAW damage in tall fescue often requires overseeding or re-sodding in order to repair the damage. A new lawn can go from fine one day, to a complete loss in a little as 24 to 48 hours. Tall fescue users cannot take the FAW threat too lightly.
We are here to help you if you have any questions about diagnosis or treatment.