Bermuda Grass is easily the primary forage crop in the country, and not a crop we need to have a new pest. The Bermuda Grass Stem Maggot (BGSM) has become a major pest, although many folks may not be aware of it, the Bermuda Grass Stem Maggot is not really new anymore. The BGSM first appeared in the U.S. in Georgia in 2010, and quickly made its way to Texas and Brown County by 2015. It is now widespread throughout Central Texas.
BGSM damage looks much like frost damage on your Bermuda. The tips will turn brown and look like they have had a light frost. On infected plants, if you pull the top leaf or two it will slip out very easily, and you can see the damage at the base of these leaves on the stems. This damage is a result of the BGSM fly laying eggs on the bottom side of the leaf, once hatched the maggot will go to the node, burrow itself inside the stem and feed on the vascular tissue, causing death to the top one to three leaves.
What are the treatment options and are they viable? We still do not have a good grasp on actual yield reduction on fields in Brown County, however, Georgia studies have shown yield reductions can exceed 50%, so treatment certainly is feasible depending on the stage of growth of your grass, and the intensity of the infestation. Due to the insect having multiple generations during a growing period, control can be difficult. A current recommended treatment consists of two separate applications of a pyrethroid insecticide. The first application should be made 7 days following hay harvest. The second application should be made one to two weeks following the first application. If your field has no history of the stem maggot then do not spray. There will be more recommendations for control as we learn more about the insect.One interesting bit of information about the Bermuda stem maggot is that it seems to prefer finer stemmed Bermuda Grass over those that are more coarse stemmed. Bermuda Grass like coastal, common or Alicia will have a higher incidence of infection than Tifton-85. But, this does not mean damage cannot occur in the coarse stemmed Bermuda varieties, we saw many infestations in T-85 last year. Like most other insects the BGSM seems to prefer the highly managed irrigated fields. On fields that are being grazed, the BGSM is not such an issue as the cattle will usually remove the top leaves where the BGSM would lay its eggs.
