Fighting Back Against the Armyworm

Ever hear of a bug called the armyworm? A type of caterpillar pest, these worms can not only damage corn and grain crops, but also adversely affect household lawns. The good news is that you can keep armyworms at bay by mixing up the grass in your front yard.

Mixing and Matching

This new development is the result of a recent study, published in the journal Environmental Entomology, which concluded that combinations of various grasses made life very difficult for armyworms. For their report, the authors analyzed six different types of St. Augustine grass. For those who aren’t botanists, St. Augustine grass is a very popular type of turfgrass species. It is a cultivar plant, meaning that it has been produced through selective plant breeding, and can be found in Florida and the Gulf Coast states.

For their study, the authors first tried out six different types of St. Augustine grass, seeking to determine if any could successfully repel armyworms. These tests revealed that none of these grasses could keep lawns worm-free. However, the story was quite different when these grass varieties were mixed together in various combinations. The armyworms steered clear of these mixed lawn samples, preferring instead to invade lawns made of single grass varieties.

An Unexpected Result

So how did the researchers test their worm larvae? One test involved feeding the worms single cultivar samples; follow-up tests altered this approach, changing the type of cultivar feed to the larvae every two days. A third experiment allowed the worms to choose their preferred grass type in controlled environments.

Other testing focused on the number of eggs laid by worms in different types of cultivar samples. The effectiveness of the mixed grass varieties surprised even the study authors. “We were most surprised by how clear the effect of cultivar diversity was on fall armyworm host selection and feeding,” stated senior author Ethan Doherty, a biological scientist at the University of Florida’s Indian River Research & Education Center. “The insects had a consistent preference for the cultivar monoculture plantings, and we saw that the effect of cultivar diversity became increasingly more pronounced as diversity increased from two to four cultivars. We didn’t expect such a clear result.”

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