Be on the lookout.
University of Arkansas Extension is advising forage producers to watch for damage from an insect that’s been recently discovered in Arkansas. Atherigona reversura, more commonly called the bermudagrass stem maggot (BSM), is the larva of a fly in the Muscidae family that’s commonly called the “shoot fly.” It’s about an eighth of an inch and colored yellow with four prominent black spots on its abdomen. University of Arkansas Extension Entomologist Dr. Kelly Loftin said the insect is native to southeast Asia; it was first detected in Georgia in 2010, and has spread throughout the southeastern U.S. It was found last July near Magnolia, Ark., and has since been confirmed in at least 25 Arkansas counties, and is believed to infest the entire state. The only forage grasses known to be susceptible to maggot feeding by BSM are bermudagrass and stargrass (Cynodon spp.). Loftin said information on control of the pest and the economic threshold of damage is limited. “Most work that has been conducted has been done in Georgia, and some work in Alabama,” he said, “so there’s quite a bit left to learn about this pest and how much damage, if any, it does…and how best to control it, if we need to control it.”
The fly lays its eggs near a node on the shoot; the larvae migrate into the node, and will kill the top two or three leaves. It’s specific to bermudagrass, and researchers at the University of Georgia say it does more damage to varieties with fine stems, like common, Coastal, Alicia and Cheyenne II. Even if actual damage to the stand is minimal, the dead top leaves produce an unsightly bale which is sometimes rejected by buyers in the horse hay market. The limited research has found pyrethroids applied at the lowest labeled rate are the most cost-effective means of control. “They’ve also found that either poor soil or poor nutrients and poor moisture can lead to a bigger issue, because it slows the growth of the plant, so it can have more of an impact on that situation,” Loftin said. The maggot is of less concern in bermudagrass that is moderately grazed, since the cows consume the larvae and eggs in the top growth; for the same reason, turfgrass sees little damage because the frequent mowing interrupts the fly’s 21-25 day life cycle from larva to adult. Loftin said if damage is found, producers should cut hay again if feasible 1-3 weeks after a harvest.
Although BSM is unlikely to be transported in cut hay – the maggot needs moisture and will die as the hay dries – Loftin warned producers to watch for another, more familiar pest that may be hitchhiking on baled hay. He said during last year’s drought many producers had hay shipped in from fire ant infested areas, under conditions that may have contributed to the spread of the exotic, imported pests. “Hay that’s actually stored in contact with the soil can become infested with entire fire ant colonies,” he said. “That’s not uncommon, and that’s why we all got concerned.”
Loftin said hay brought in from Louisiana and Mississippi, and likely from South Arkansas, carried the pests, and hay growing areas of Mississippi are known to be infested with black imported fire ants, hay from Alabama is of less concern, because that state has established a permit system where hay bales are certified to be fire ant free. “Today, we’re not aware of any new infestations resulting from infested hay, but we can’t let our guard down,” Loftin said. “We need to keep looking.”
