In the Tampa Bay area, one of the most prevalent turf damaging insects we see is the lawn caterpillar, also commonly referred to as worms or caterpillars.  Lawn caterpillars are regularly found damaging St. Augustine, Zoysia, and Bermuda grass.  This article covers a basic understanding of the insect, identifies what worm damage looks like, and explores its relationship to and implications in the lawn.

Understanding the Lifecycle

As turf-damaging moths fly over the lawn and landscape, they drop tiny eggs onto the grass canopy.  These eggs hatch into small caterpillars, and they begin to feed on the grass leaf blades.  Eventually the worms pupate into moths, and the circle of life continues.

Identifying the Problem

Up close, the damage associated with lawn caterpillars is very easy to identify.  If you look at the edge or margins of the leaf blade, you will see what appear to be bites taken right out of them.  Sometimes you will notice what appear to be “shotgun holes” in the leaf tissue.  This is where the leaf blade was fed upon when the leaf was closed.  From afar the worm damage, in general, can give the lawn a dry, hazy, patchy, and even defoliated appearance.  Should you see these signs, a closer inspection while down on your hands and knees should quickly confirm or deny the presence of worms.  Although you may or may not actually find worms (some hide deep in the thatch layer and their color is often the same as that which they eat), the presence of chewed leaf margins is enough to confirm the recent activity of worms. In the most severe cases, worms can defoliate a lawn with amazing speed;  however, if the damage takes place at a time when the lawn is actively growing, complete recovery can be achieved in 1-2 weeks.  Study the pictures included here, and you should be able to identify the damage should you encounter it on your own lawn.  For further confirmation, you can flood a suspected area with 1-2 oz. of dish soap (like Lemon Joy) in 2 gallons of water.  This drench solution will drive insects upwards and make them move around more vigorously, thereby making them easier to find.

Pictured above: Damage from worms feeding on the margins of St. Augustine grass leaves.

Treatment

Controlling active worms can be achieved, provided you can get a suitable active ingredient in place and keep it there for about 24 hours.  The worms themselves are very susceptible to most common insecticides.  The trick is in getting the material down in sufficient volume (a hand-held sprayer may not be sufficient).  In some cases, the amount of worm feeding may not even warrant a treatment as it is so limited, and actively growing grass usually has the ability to outgrow mild levels of worm feeding.

Turf Recovery

The actual damage from worms is rarely a death sentence for a healthy turf grass since the damage is to the foliage or leaves of the plant and leaf regeneration is ample during the growing season.  Slower-growing turf types will take longer to grow out of the damage than will quick-growing types.

Pictured above: A dwarf variety of St. Augustine grass with active worms feeding inside the white box.

Often people think that moths flying over the lawn at randon times of the year indicate that there are worms feeding on the lawn.  This is not necessarily the case.  There are untold varieties of moths found outdoors and not all of them are implicated in damaging grass.  Furthermore, it is possible that moths you see today are not an indication that there are worms actively feeding or that there are enough worms feeding to justify a treatment.  If the moths you see today are the culprits that damage turf, remember that eggs they lay will need time to hatch prior to feeding.

-- Green Solutions Lawn Care & Pest Control is an award-winning provider of lawn care and pest services in the Tampa Bay area. Our staff boasts two university educated turf agronomists and a university educated horticulturist. We offer fertilization, weed, insect and disease control programs for residential and commercial clients. We also offer general household pest control services. We have developed “GREEN” options for most of our services.  We happily provide free estimates.

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