Editor’s note: The following information is supplied by Wayne Dellinger, Union County Extension Educator, Agriculture and Natural Resources.
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The fall armyworm has taken over many fields and lawns across Ohio and, more recently, Union County.
Identified by daytime feeding and a very distinct inverted “Y” in their heads, the insects were named because of their tendency to move in masses rapidly across areas, feeding on more than 80 different crop species.
They are not new to the area, but every three to five years the area experiences a larger outbreak.
Armyworms are not native and do not overwinter here so they must travel from the south, where they enjoy the warmer weather year-round.
The insects being seen right now are the second generation of this year’s population. They most likely came in on a southern storm front or the jet stream.
If Union County has a warm fall season, a third generation could emerge.
Fall armyworms arrive in the area as moths that lay egg masses of 100-500 eggs on leaves that hang over turf areas. If a suitable host is not located, they will lay egg masses on blades of grass.
These eggs hatch in five to seven days and then take three to four weeks to complete their larval, or caterpillar, stage.
This is the period when the damage is done to crops and turf.
If the food source is used up for the caterpillars, they then turn carnivorous, and the larger larvae eat the smaller larvae to complete their cycle. Then they dig into the soil and pupate for about two weeks and emerge as moths again.
In lawns, the damage occurs when the canopy, or blades, are removed and the crown and roots are exposed.
The crown is the portion of the grass right at ground level that is the growing point for the plant. Once it is exposed to direct sunlight, the plant will likely die.
If the canopy is removed, it is recommended to irrigate and fertilize to keep the crown from dying and to get the plant growing again.
If the canopy is not lost but caterpillars are observed, insecticidal treatments are effective.
Pyrethroid applications are somewhat effective but there is some resistance developing in this year’s emergence. If resistance is noticed, Acelepryn or Tetrino would be effective. Azadirachtin products are also effective but may be difficult to locate.
If the insecticidal treatment is effective, fertilizing would be the next step to help the grass recover.
Lawns or turf areas that are lost to the fall armyworm should be reseeded with a slit/slice seeder. A turf-type tall fescue is recommended. Most of these produce alkaloids that are toxic to armyworm.
In agronomic situations, the fall armyworm will damage corn by entering the ear and feeding on the silks and kernels as they develop. Insecticidal control once they are inside the ear is much more difficult. Many hybrids of corn are labeled for armyworm control.
Major damage may occur in forages where the threshold for insecticidal treatments is two to three caterpillars per square foot.
In forages, an alternative to insecticide application would be to mow immediately. Once the grasses are cut, they are less attractive to the armyworm. Regrowth should be closely monitored.
While soybeans are not the food of choice for fall armyworms, the Union County Extension Office has received reports of them moving from hayfields to soybean fields once the hay is mowed. They were observed feeding on the pods of the beans rather than the foliage. Soybeans earlier in maturity should be monitored for any activity.
For more information, please call Wayne Dellinger at the Union County Extension Office at 937-644-8117 or email dellinger.6@osu.edu.