Fall Armyworms March Across Ohio

From friend and colleague, Ron Wilson

Sep 3, 2021

OSU Extension county offices across the state are receiving e-mails and phone calls about Fall Armyworm (Spodoptera frugiperda, family Noctuidae) causing substantial injury to turfgrass. Thus far, it appears that fall armyworm is the dominant culprit rather thanYellowstripedArmyworm (S. ornithogalli) and Common Armyworm (Mythimna convecta).

Fall and yellowstriped armyworms are semi-tropical species that “fly” north each season. We often get both species in Ohio in August and September when they replace black cutworms that most superintendents see on their greens and tees. Both species also attack field crops, especially corn and small grains.

Every few years (usually 3-5 years), we get a massive buildup of these pests in the southern and transition turf zones. Reports of heavy armyworm activity have been coming out of Oklahoma to North Carolina for the last two months.

We believe adults from those outbreaks were picked up in the storm front that came from the south across much of Ohio about four weeks ago. The adults of these moths have been known to travel 500 miles, even more, in 24 hours. They can get into the jet stream and move vast distances, then drop down to find suitable host plants.

Adults tend to lay eggs on the flat leaves of trees and flowers that overhang turf, especially turf that has been recently fertilized. Each adult female can produce an egg mass that contains 100 to 500 eggs. The females are also attracted to night lights, and they will attach their egg masses to the light posts! If there are large areas where no plants or structures are overhanging the turf, the females will lay strips of eggs on grass blades.

The eggs hatch in 5-7 days and the larvae usually take three to four weeks to complete their 5-6 larval instars. The mature larvae dig into the thatch or upper soil and pupate without making a cocoon. The pupae take about two weeks to mature. So, the complete life cycle takes about 50-60 days.

Direct Control

Armyworms are so named because of their habit of movingen masseto greener pastures once they’ve depleted their food supply. It is not uncommon for the caterpillars to move from field crops into nearby turfgrass.

Once they move into turfgrass, the caterpillars will continue feeding until there is no more food or they complete their development, whichever comes first. If the plant food is exhausted, the armyworms will become meat-eaters with the larger caterpillars eating the smaller caterpillars to complete their development.

Turf that has had the canopy removed by the caterpillars will have the crowns and upper roots exposed to direct sunlight. The crown rests on the soil surface and is the growing point for both blades and roots. On sunny days, the area where the crowns are located can easily reach 120 to 130-degrees F which will “cook” them or dehydrate them. Loss of the crowns means the loss of the entire turfgrass plant; the turf is dead.

Thus, the first step in protecting the turfgrass plants is to kill the caterpillars before they completely devour the turfgrass canopy. This involves the direct application of insecticides.

Most turf managers are appearing to have success with their pyrethroid applications. However, we are getting reports from the agricultural markets that pyrethroids are not working well, so alternative chemistries should be considered.

Ron Wilson

Fall ArmyWorms Video

Sep 4, 2021

Dr. Dave “Bug Doc” Shetlar, Joe Boggs and Curtis Young released a BYGL Alert for the critters with recommendations on control and management of damaged turf. 

View the video here:  https://bygl.osu.edu/node/1859

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