Fall can bring cooler weather and rain as cold fronts blow in. Unfortunately, early fall rains are a prime breeding ground for fall armyworms. Armyworm larvae hatch after fall rains and their sheer numbers can overwhelm and damage your lawn within days, making them the insect that causes the most damage to home landscapes. Each lifecycle from egg to adult takes approximately 28 days which means that several generations of armyworms can grow and do damage during the fall months with cooler temperatures. Armyworms attack many different types of plants. In home landscapes armyworms are attracted to warm-season turfgrasses, especially bermudagrass.
Unfortunately, the issue with identifying and treating armyworms is that most homeowners don’t notice the damage until it is done, when the larvae are mature and have finished feeding. Take note of damaged areas in your lawn that are off-color or that turn brown as the armyworms start by damaging strips of leaf tissue until they have destroyed entire leaf blades. Armyworms are most active early in the morning or late in the evening, but they can feed throughout the day. Mother Nature tries to control these outbreaks; as these armyworm caterpillars mature, you may notice many bird species move in, especially blackbirds and grackles. These bird species can eat whole populations of this pest within minutes so capitalize on this natural predator if you can. Wasps, flies, and ground beetles also consume large numbers of pupae and larvae.
If you identify the problem early, before armyworms have decimated your turf, products containing Bt (Bacillus thuringiensis) including DiPel and Thuricide work well if applied before extensive damaged is done. This biological product is not harmful to animal and insect predators; however, always read and follow the product label and instructions for application details.