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Perennial ryegrass and large leafed white clover

Starting in September, many livestock producers, hunters, and wildlife enthusiasts throughout Alabama will begin planting their cool-season annual forages in pastures and food plots. This year, growers should be aware of the above-average infestation of fall armyworms being seen across Alabama and how these infestations could affect their cool-season forages.


Fall armyworm damaged pastureFall armyworms have had a devastating effect on pastures, hayfields, row crops, vegetable crops, and home lawns for much of the summer. Entomologists are indicating that their impacts will likely be felt for many weeks to come and possibly all the way to Alabama’s first frost. These pests feed on a variety of forage crops, but they prefer tender, lush foliage of forage plants and some other crops. Cool-season forage species–such as oats, wheat, rye, ryegrass, and many types of legumes–are ideal hosts for fall armyworms. With the exceptional number of armyworms people are seeing this year, producers should expect damage to any host crop, even the less desirable ones.

Fall armyworms will defoliate perennial forages, but the forage will survive, and regrowth will occur within a few weeks. Unfortunately, many of the cool-season forage crops used in pastures and food plots are annuals and do not have the root structure developed to withstand the attack. Annual plants are young when armyworms strip foliage from the plants down to the terminal bud, and it will often kill the plant entirely.

Management Considerations

There are several management considerations hunters and livestock producers may want to think about before planting winter annuals this year.

Delay Planting Date

As the temperatures lower in the fall, the likelihood of major impacts from fall armyworms declines but does not go away until the first frost. Most hunters will plant their food plots at a time where it would grow to produce adequate volumes of forages to attract wildlife prior to the start of hunting season. Likewise, livestock producers will plant cool-season forages in time for them to utilize by late fall and early winter. This can likely still be accomplished by planting later in the fall when pressures from armyworms have diminished. However, for livestock producers, a delayed planting may push back having forages ready for livestock farther into the year but this may be better than losing an entire stand from fall armyworm attacks.

Scout Frequently for Fall Armyworms

Growers should check fields frequently for fall armyworms until frost. Most fall armyworm damage often seems to appear overnight. High populations can decimate a field in just a few hours, especially when caterpillars are larger. Scouting should be done at least every 2 to 3 days, early in the morning or late in the afternoon when the caterpillars are more active. Look closely at both the plants and on the ground. Early-stage caterpillars are hard to see as they are as small as ¼ inch long and their green and yellow color is camouflaged with the plant colors.

To effectively find caterpillars, people want to be on the ground in the field. Scouting from the roads in trucks and ATVs won’t cut it. Sweep nets are a highly useful tool in finding the presence of  fall armyworms. Many county Extension offices have sweep nets available to loan. The presence of groups of birds in fields is often another indicator of armyworm population. However in years like this with such high populations of armyworms, by the time the birds show up, the damage to the field is already done.

Prepare to Apply Insecticides

Growers that plant cool-season crops should be prepared to apply insecticides if armyworms are found. This is best done with a boom-type sprayer that calibrated to apply accurate amounts of insecticides. Growers should check insecticide availability prior to planting. With the current widespread infestations around the South, insecticides are in short supply. Growers may want to consider securing insecticide prior to planting as a safety measure.

There are several effective products labeled for fall armyworms, but the key is applying when the caterpillars are small. Once fall armyworms get larger (greater than 1 inch), they are harder to kill and cause substantially more damage. Growers should also have their spray equipment calibrated and ready to use at a moment’s notice given how fast armyworms move through fields. See Insecticides for Pasture Control of Fall Armyworms for a list of control products labeled in Alabama.

More Information

In most years, fall armyworm infestations are something that livestock producers have to consider, but not to the extent that they are seeing this year. On the contrary, few hunters and wildlife enthusiasts ever worry about fall armyworms destroying the food plots they plant, but this year is an exceptional year for infestations. By utilizing the considerations mentioned above, growers can help protect their investment in cool-season annuals as well as help ensure the availability of the forages for livestock and wildlife alike.

Information on many of the cool-season annual forages planted in Alabama, is available in the Alabama Extension publication Alabama Planting Guide for Forage Legumes. For hunters, more information about wildlife food plots is available in the publication Plantings for Wildlife.

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