Well FRASS, what is eating my crop!?!

This year, farmers across Ohio have been reporting some serious infestations of Armyworm. Armyworms overwinter in the southern US and adults begin to migrate North in April and May. Females like grassy areas to lay their eggs and this often means infestations in an area can begin in your cover crops (maybe already planted to corn), wheat, and possibly other small grain, fields. Once larvae hatch, they will feed for around three weeks, and according to reports from Kansas State University each larvae can feed up to 43 linear inches of wheat leaves in 1 night. If populations reach high enough levels and are left unchecked in your wheat this can cause issues in neighboring corn fields. Scouting in you cover crops, wheat, and corn fields should begin early in May and continue throughout the season. The earlier you start scouting the better because 1) smaller caterpillars are easier to kill and 2) larvae nearing maturity (1¼ inch or more in size) have already done most of their feeding. The larvae picture below is close to 2 inches long. Some tips to remember for scouting in both small grain and corn fields:

The best time to scout is during the cooler parts of the day, at dawn and dusk. Like us, armyworms don’t like the heat of the day and will take shelter in the corn whorls, under debris in the field, or at the base of the plants. As you scout start at the bottom of the plant and work up, making sure to focus on those areas, as they might not be noticeably feeding on the foliage.There are thresholds for both Wheat and Corn.

In wheat, the threshold for treatment is when there are 2 to 5 larvae per linear foot (see picture above, armyworm are circled in red). The lower numbers are commonly used as a base when wheat prices are higher. If armyworm larvae have reached maturity (1¼ inch or more in size) treatment in typically not economical because their feeding is slowing as they prepare to pupate.

In corn, as you scout early, if armyworm feeding damage is found on 15 to 20% this could be the first signs of a problem and fields should be checked regularly. As the season progresses, if defoliation is increasing then treatment may be warranted if larvae less than 1¼ inch long are found on 30% of plants with 5 to 6 extended leaves OR when 1 larva is present on 75% of plants. If left unchecked, yield loss can occur if defoliation is near the ear zone before hard dent.
The last thing to consider before treatment is size of the armyworm. If the armyworms are bigger than 1¼ inch (as seen above) they have completed most of their feeding. Treatment is not considered profitable at that point, because the damage is already done.

If you decide to use an insecticide, Fastac® CS is an effective tool with excellent knockdown and residual.
Frass happens, but it doesn't have to happen in your field. Contact your local BASF Rep to learn more.