Bermudagrass Stem Maggots are here and already causing damage. If you have not yet applied a pyrethroid to help control flies be sure to scout hayfields and make sure you are not too late. Once the damage is visible it is typically too late to control them for that cutting. Below are some photos taken in Ben Hill and Irwin County hayfields with noticeable damage. Frosted brown tips that pull out of the stem are positive ID of BSM damage.
To better understand control methods, let’s look at the life cycle of the BSM. The maggot which caused the damage is actually the larval stage of the BSM fly. There is no way to control the maggot so instead we control the adult fly and break the life cycle. The fly lays her eggs in fields with bermudagrass. Two to three days later, the maggots hatch and bore into the bermudagrass leaf whorl. After the larva has damaged the grass, it crawls out and goes into the ground to pupate. Approximately 7-10 days later, it emerges from the ground as an adult fly. (This is why spraying after damage is noticed may not be as effective. )
An insecticide application is recommended 7-10 days after cutting to control the adult flies that are emerging to reduce populations of the BSM in your bermudagrass hayfield. If there are other fields nearby that have shown damage, a second spray 7-10 days after the first may be needed to control the BSM.
The recommended chemical control options are various pyrethroids for example: Lamda-cyhalothrin, Bifenthrin, Zeta-cypemethrin, and Cyfluthrin. This is not the complete list of pyrethroids just some examples.
Patchy growth, no growth, or stunted growth have been some common occurrences in hayfields I have checked recently. Hayfields with adequate potassium applications are still showing signs of potassium deficiency. A lot of that seems to be our late cold spells followed by many cool nights and then dry periods. The cold weather has also allowed rye grass patches to persist later into the season and compete with Bermuda grass for nutrients. Recommendations from Forage Specialist dr. Lisa Baxter are to apply half of the recommended Potassium now and the rest later in the season based from your soil samples. Hopefully now that we are having some warm weather and a little rain hayfields will improve.