Fall Armyworms: Pest Control for Larvae and Moths

College Station has frequent fall armyworm problems. With our warm and humid climate and local agricultural fields, fall armyworm moths can quickly find places on your lawn to lay their eggs. Once the larvae hatch and feed you’ll see the reason that they’re named after army soldiers. The most effective pest control solutions involve a deep understanding of the enemy and all the techniques that you can use to clear them from your property. If you suspect you’ve been having issues with fall armyworms, read on to discover how to treat them at every stage of development.

Identifying Fall Armyworms

Image Source: Texas A&M Agrilife Extension

Fall armyworms share some similar traits with other pests across your lawn, like sod webworms. We actually wrote an article on the differences and similarities between the two pests which you can read here. You’ll note that, despite the similar name and look of damage, fall armyworms have some key distinctive traits that you can look for to identify them as the main issue.

Their larvae are long, thin caterpillars with greenish-brown bodies. The heads have a distinct “Y” shaped marking that sets them apart from other larvae. Growing between 1 and 1 ½ inches, they also are pretty large compared to other larvae. On your lawn, you should be able to see them feeding on grass if you investigate. When they grow into moths, they have wings ranging in color from white to tan to brown and long wings. Fall armyworm moths are very strong fliers and will travel miles for appealing lawns on which to lay their eggs. When they hatch, especially in late summer and early fall they will start to eat away at your lawn. They reproduce quickly and can have multiple generations within one growing season, especially if the conditions are ideal for them.

Image Source: Smithsonian Magazine

Signs of damage come from the larvae eating away at the stems of a lawn’s grass. Blades will have a jagged or bitten edge and can quickly brown. This results in brown patches sprouting across your lawn. Unlike with other pest species, armyworms move quickly and precisely. Instead of random or irregular patches of damage, they will usually spread uniformly from one corner of your lawn to the next in an even progression. It’s also important to note that they can strip lawns in a matter of days, depending on the severity of the infestation. The damage might look like it’s something else like drought, but once you recognize the telltale signs you need to act quickly. Once the infestation gets severe, it can destroy the grass on your lawn for good.

Treating Fall Armyworm Larvae

Image Source: Texas A&M Agrilife Extension

When it comes to treating them before they grow into moths, there are a few ways you can kill them or halt their growth before they eat your whole lawn.

Pesticides

It might seem like pesticides are the only tip that people recommend for pest control. This can be annoying, both for application and if you prefer more natural forms of lawn care and pest control. However, with how much damage a severe infestation can do, it’s possible it might be the only form of treatment for fall armyworm larvae.

Make sure to read the directions on the packaging and choose a brand that notes specifically targeting fall armyworms while also being relatively safer towards beneficial bugs. The best times to apply are when they are most active with feeding, which is the late afternoon and early evening. They are generally nocturnal, so review the weather and make sure that the applied product will not be washed away with rain during the night. Fall armyworms are also generally more active with humid but mild temperatures.

IGRs

Instead of killing them off, IGRs work to prevent future infestations and slowly kill off a current one. IGRs, known in full as insect growth regulators, disrupt the development of larvae into moths and slowly destroy them as they grow and progress. They do this by disrupting key stages of development, like molting and the pupal stage that leads them to hatch. Not only does this kill armyworms before they grow into moths, but some forms of IGRs can keep eggs from hatching as well, nipping the next cycle in the bud. 

For your pesticide or treatment, look for IGRs in the ingredients and apply as directed. Know these will not kill on contact, so severe damage might still progress. However, this is able to interrupt the cycle without harming beneficial bugs like ladybugs and lacewings. Also, if you’ve had multiple infestations of fall armyworms, adding IGRs can not only help to kill them in the future but also will ensure that the larvae don’t develop a resistance to your pesticide.

Nematodes and Bacillus thuringiensis (Bt)

We also discussed this when it comes to treating sod webworms, but Bt nematodes are an effective, natural way to kill off fall armyworms as well. The same species of nematodes are great at destroying fall armyworms from the inside out after eating. They also spread out in your soil after killing their host, which helps to prevent future infestations in the coming seasons. You can find these in similar areas to where you buy pesticides and apply them according to the packaging.

Your Hands (yes, really)

The above solutions focus on a severe infestation and how to treat a huge issue. You might even need multiple application of these methods, depending on the severity and any other eggs laid in the cycle. However, as noted above, these are big larvae that are quite noticeable on the lawn. Can something be done against them in the early stages?

Yes, in fact, something can be done. If you notice a small number of fall armyworms on your lawn, whether for the first time or after an old infestation, treatment can be as simple as picking them up. Like with pesticides, the best times to look for the larvae are the early afternoon and evening on cooler days. You could also draw them to the surface of the lawn with the soapy water test, which we outline how to do in this article on chinch bugs. When you see a larvae, pick them up and place them into a container of soapy water. Once you are sure they are dead, you can dispose of them. Hand-picking like this likely will require you to check every few days. It’s also not as practical if you have a large infestation. However, especially if you want to avoid pesticides on your lawn, it can be a simple and clean way to take care of a small infestation.

Treating Fall Armyworm Moths

Image Source: Texas A&M Agrilife Extension

When it comes to using pesticides on moths, make sure to read your insecticide directions carefully. While some of the active ingredients are effective against both the larvae and the moths of fall armyworms, some work specifically for one stage of development. It’s also important to consider placement differently. Instead of looking for where damage is or where you can see larvae, apply where your grass is extra long or where there has been debris or thatch buildup. Moths want to look for attractive patches to lay their eggs, and otherwise might not interact with damaged sections of your lawn.

There are also a few different measures you can take to keep the moths away from your lawn. 

Beneficial Birds

You may notice more birds poking around your lawn when it is infested. This is not only a good sign that a problem is starting to get severe but can help treat the problem in the long run. Invest in bird feeders or houses to promote their presence on your lawn. They will prey on the larvae and the moths as they come to your lawn to lay eggs. This helps to solve the problem of future generations laying more eggs.

Light Traps for Moths

Other traps for moths will work on fall armyworms once they reach their adult stage. A light trap in the right spot will draw in the moths before they get the chance to lay eggs on your lawn. After they are zapped, this will help to prevent the new generations from spawning across your lawn.

Preventing Fall Armyworms

It’s important to note that these methods, regardless of how effective they are for you personally, might still need to be applied multiple times during a season. Because of the possibility of other moths laying their eggs on a weakened lawn and the multiple generations in one reproductive cycle, it’s easy for fall armyworms to hatch after treatment or reinfest your lawn. To prevent your lawn from being infested or reinfested, here are some good things to do for your lawn and grass.

Good Lawn Health Standards

A healthy and clear lawn is not very appealing to pests. While they want to eat healthy grass, a healthy lawn is resistant to their attempts to host and they will easily be picked off by beneficial bugs for resources or space. This means that employing good lawn care and maintenance practices is the best way to keep pests off of your lawn.

Dethaching, aeration, and mowing your lawn to an appropriate height are all especially effective against fall armyworms. Fall armyworms love extra-long grass and thatch because debris gives them places to hide above the soil when they are not actively feeding. Aeration also helps your lawn’s roots to grow thicker and stronger to be more resistant to pests. Mow your grass to an appropriate height for its type, especially for warm-season grasses that fall armyworms target.

Watering is also something important to track for your lawn. While a dried-out lawn is weaker and more susceptible to pests, fall armyworms love humid conditions and overwatered grass. Make sure that, if you are manually watering your lawn, that you are not overwatering your lawn. After a storm, keep track of your lawn if you have had issues with fall armyworms, as post-storm conditions are the ideal conditions for fall armyworms and their moths might have been driven to your location.

Fertilization for Pest Control

After an infestation, helping your lawn to heal will do a lot with your preventative treatments to keep fall armyworms away for good. This is where fertilizer can help to give your lawn a nutrient boost and grow back faster. Providing a chance for your remaining grass to bounce back is easier than resodding or planting your lawn and allows your lawn to avoid the stage of trying to reintegrate with your soil. Make sure fertilizer is not high in nitrogen, which could provide tender growth and more pests to visit.

The Local Pest Control Experts

Between preventive treatment, lawn care after damage, pest control, and identifying the source of lawn damage – there’s a lot to juggle when handling an infestation on your own. For any stage of the pest control process, The Fertilizer Guy can be of service to you! Fertilization and every stage of pest control, from identification to prevention, is our specialty. We’ve served the College Station and Bryan areas for years, so we also know local conditions and what to expect on your lawn. For help of any kind or more information, contact us today!