Cover Story

o Fall armyworms overwinter most years in southern Texas and Florida and their northern migration can be influenced by weather patterns. We do not have the ability to accurately forecast fall armyworm problems in advance, so timing-wise they can sometimes surprise us with their damage.

o Not unusual at all. Remember, the adult life stage of a fall armyworm is a moth. Moths are capable of flying large distances in a relatively short period of time. Many insects exhibit flying behaviors associated with both localized (short) and long-term migration. Female moths fly to an area with an abundant food source (fresh, green turf, for example), lay their egg masses on the flat side of a building, fence, sign, or large leaf, and when the eggs hatch, the larvae drop to the turf below and immediately start feeding.

o 2021 had the worst outbreak of fall armyworms on record, in many areas. Fall armyworm populations and damage were on a scale that was very surprising! Areas of the upper Midwest and the Northeast suffered turf damage to both warm- and cool-season turf like they had never seen before. Some of the problems came from populations originating in Texas and some from moths that started out in Florida. These different “sources” potentially exhibit different traits for feeding preferences, like the damage we observed with seedlings and overseedings, and insecticide susceptibility.

o During “normal” years, fall armyworms are more likely to cause issues in turf that has had some mechanical disturbance, like in areas of new construction. They are generally more of a problem in newly-seeded or sodded areas.

o Because fall armyworms can cause a lot of damage in a short period of time, it is best to treat as soon as you notice activity.