Danvers Mail

Armyworms Invasion

Armyworms have invaded hay fields all across Central Illinois, and many local farmers took action against the insect this past week. The armyworms, which are fall armyworms or scientifically named spodoptera frugiperda, invade in late summer or early fall. They are unable to survive the cold winter months. The fall armyworm prefers drought-like conditions. They are usually most active early in the morning and late in the afternoon. 

Armyworms have shades of brown, green, and black on their body and a distinct white line that forms the letter “Y’ onto their face. Behind the white line that creates a “Y”, there are three white stripes that run down the back of the caterpillar. At first they are very small and will cause little plant damage, causing them to go unnoticed. Once the larvae have fed for 2-3 weeks, they start to leave a big impact. The oldest caterpillars can eat as much as all of the other ages combined in four days of feeding. The one to one and a half inch long insect has a large appetite and lots of armyworm friends that do too. Armyworms can damage entire fields in a very short amount of time, and they are able to move over to the next crop after they have left their mark. In a hay field, all green material may be removed because of the armyworms, to where they leave only tough stems that are a few inches long. Brown patches will appear in the field and can increase in size quickly.

Once an armyworm larva is done feeding, it tunnels into the soil and enters into the pupal stage. After about 10 days, the pupal stage is complete, and the larva appears as a moth. The moth has a dark gray pair of wings with a pattern of dark and light areas. The moths are active at night to feed on nectar. They deposit egg masses to repeat the armyworm life cycle. One female moth can deposit up to 2,000 eggs. This cycle will repeat three or more times per year, meaning there can be three or more generations of armyworms per year if not prevented.

2021 has been a “breakout” year for the fall armyworm. A “breakout” year happens when an unusually high population of the insect survives the southern winter and makes its way north. Danvers farmer, Dan Craig, explained that he has never had to deal with an armyworm infestation in his 15 years of farming. Craig was scouting his hay fields and found one field with 75% damage and armyworms in other fields. He decided to spray every acre of alfalfa he has and some bean fields to protect the undamaged crops from the armyworms. Another local farmer, Carl Neubaurer, reported his experience this week with the armyworm problem. Neubaurer first heard about the prevalence of armyworms in Central Illinois from agronomist reports and fellow growers. He first heard the news on Wednesday night. He checked his fields first thing Thursday morning and found a large number of the insects. He plans on spraying all of his fields as precaution. Neubaurer’s reasoning for this is, “The significant thing in alfalfa this year is that the weather has prevented us from getting a good amount of quality hay. We didn’t want to take the risk of armyworms making us lose more than we already have.”

The spraying process for armyworms is similar to other chemicals that are commonly sprayed on crops. Craig explained that the timing of spraying is really important. He stated, “You have to be worried about the harvest interval once you apply the chemical. If it is too close to when you need to harvest, you reduce the chemical to not interfere with the harvest timing. So, you select the chemical based on when your harvesting window is going to be.”

This isn’t just a problem for farmers. Homeowners that have gardens should be on the lookout for this problem too. Certain species have a distinct taste for a certain plant or vegetable, but some will eat anything red, yellow, or green. You may find armyworms hiding under plants or garden debris during the day. A garden dust or insect garden spray (spinosad) can be beneficial in fighting the insects, but there are other, more natural ways to combat your problem. Most importantly, armyworms are able to do a lot of damage in a short amount of time, so if you have an armyworm infestation is it important to act fast.