If you’re a Florida resident, you know just how hard it is to keep your lawn alive. From one season we have mild weather and no rainfall. In the next, temperatures will regularly reach over a hundred degrees and state-sized storms will drench them through. Being a species of turfgrass in Florida isn’t easy. That becomes doubly true when you take into account the Florida Fall armyworms that are creeping their way across the state. That’s why they’re going to be our subject for today.
Florida Fall Armyworms: Overview
In the southeast, fall armyworms are an unfortunate fact of life. This chronic pest can cause severe damage to grass and other kinds of turf. The adults of this species are an ash-grey moth with a small wingspan. They’re grey, active in twilight, and are nectar feeders. The females lay eggs at night in masses of several hundred, meaning that this infester can become saturated in an acre of grass in no time at all. Female adults prefer to lay their eggs on tree trunks, fence rails, and the underside of tree limbs. However, they’ll lay directly on the grass if they need to. All of the eggs will hatch within two to four days at roughly the same time.
What emerges are tiny, light-colored larvae with black heads. They’ll spin down to the ground on silken webs and immediately begin to feed. As they grow, they darken in color and develop noticeable stripes. When fully grown, the larvae may be larger than adults and vary in color from light green to almost black with stripes running along the body. They can also be easily identified by an inverted “y” shape on their head capsules.
Under summer conditions, caterpillars feed for around fourteen days, with most of the feeding done in the last four when the caterpillar is fully grown. The fully-grown larvae then burrow into the soil to form pupae, emerging as adult moths in around ten days during the summer.
Armyworm Damage
The fall armyworm eats grass of all kinds.
Florida fall armyworm damage varies widely in how it appears. The severity and look of it depends on the type of grass they’ve infested and your management practices. In fields that are closely grazed by cattle, the grass may seem to thin out and develop brown spots. If you’re not used to fields, you can see similar damage sometimes on golf courses. These spots appear to be brown or burned out. This is because the armyworm larvae chew off the tender foliage, which means that this pest often resembles simple drought damage at first.
In pastures or actual hayfields, almost all tender green material will be destroyed. This pest is ravenous and numerous and will leave only a few tough stems protruding from the soil. Brown patches can appear in a field like this and quickly spread outwards. Established, healthy grass will likely survive an infestation, but the complete defoliation caused by a large infestation can damage and leave grasses vulnerable to perishing in other ways.
Damage from Florida fall armyworms on newly established grass is much more severe. Winter annuals, tall fescue, or orchardgrass are all at increased risk. Seedlings of these plants are small when armyworms reach their seasonal highs. This means these crops can be stunted or killed if armyworms are successful in their infestation.
Behavior
The armyworm is in the same family as the more notorious pest, the cutworm. They damage grass in a similar way, by chewing on plant tissue. This pest is most active early in the morning, late afternoon, and early in the evening. However, on tall and unmowed grass you can see them eating throughout the day. In freshly mowed or grazed grass, however, they spend the heat of the day deep in the sod.
The damage from this pest also appears almost overnight. That’s because young armyworms’ don’t eat much. Nearly all damage caused by Florida fall armyworm caterpillars that are near adulthood. Over those four days of feeding I mentioned above, the caterpillar eats more than it did in its younger stages put together. Another reason the damage can seem so sudden is because that the larger worms will migrate to more abundant food sources. Defoliated fields by older generations will push them outwards, where they’ll graze, pupate, and move on almost as suddenly as they appear.
What can I do about Florida Fall Armyworms?
Unfortunately, once you notice a brown patch of grass it’s probably too late. Armyworms, at that point, have likely already burrowed beneath the surface of your lawn and have begun to pupate. Wait to reseed your lawn, and contact a pest control specialist asap. As a layman, you’re going to be dealing with management, not elimination. This will not be a pest that you’re going to be able to get rid of on your own.
Instead, look for even earlier signs. For example, a large number of birds foraging in your yard may mean that they’ve found a significant food source- such as white grubs or the armyworm.
Further north, all you’d really have to do at that point is wait for the cold. This is a pest that dies en masse with the frost. However, down in Florida, you’re likely going to have to contact a pro like I mentioned above. You can try to use your own insecticides, however, that’s a risky proposition. This is a fast-breeding insect, which means it can develop resistance or an immunity within a few generations.
Not only that, but if you use broad-spectrum pesticides you’re putting your own health at risk. These are widely known to be damaging to human health, and you can expose plenty of non-armyworm insects. This includes things like predatory insects, which help control the pests, as well as pollinators like bees and butterflies. Not only that, but improper use that doesn’t kill an armyworm can end up killing the predator that will come along to eat it. So like I said, be safe and stick with letting the pros handle it.