One thing I really enjoy on a nice weekend drive is to see all the Seminole County countryside. There are so many different crops growing at once and almost none of them look the same. My little girl is getting to the age where she loves to tell me what a crop or animal is as we pass by. “There’s corn daddy” or “look daddy, cows” or some other thing little kids love to point out. What I like to see is the bermudagrass hay fields. Bermudagrass is a staple in the agriculture community and fed to livestock all across the southeast. Seminole County produces about $650,000 worth of hay each year, with bermudagrass being a good chunk of that. Our bermudagrass hay has a major enemy though; the bermudagrass stem maggot.
The bermudagrass stem maggot is an invasive pest from southeast Asia and is a relative of the common house fly. In its native land it’s not considered a pest or a beneficial insect. It normally feeds on wild, non-agronomic vegetation that is of no concern. So, when researchers found this pest in Georgia in 2009, attacking bermudagrass hay, there was no real course of action. With very little research on how to control the fly, and no known natural enemies, the fly for the most part has been able to destroy hay and lawns across the southeast.
I worked on several studies with the stem maggot over my three years at UGA. We did life cycle studies, soil pupation work and also the effects of harvesting on fly populations. We compared grazed bermudagrass pastures to hay production fields to monitor the difference in populations over a growing season. The pastures would serve as a somewhat “control” since the flies had constant sources of fresh grass growth to live and reproduce. We tracked their populations against the populations in the harvested fields to show the impacts harvesting had.
The main take away from our study was that harvesting hay did have an overall impact on populations and damage. When farmers were able to harvest their hay in a timely manner, roughly 5-6 weeks, the flies were not able to reach population and damage levels the pastures did. However, when hay fields were not harvested properly, the flies had the opportunity to continuously reproduce and increase overall damage. And when we get to the last cuttings of the year, you could see a huge population and the last harvest (or so) could be significantly impacted.
The next time you here a farmer talking about seeing stem maggot damage, ask them when they cut hay last. If it has been awhile, you’ll know that what’s to come won’t be any better. And if you do think you have high levels of the fly, please give me a call at the extension office. We can monitor your populations and help keep this pest at bay for now. Thank you for reading and stay safe out there.