By Chris Tyson
Bermudagrass Stem Maggot Damage
Last week, I found some Bermudagrass Stem Maggot Damage in a Bermudagrass hay field. Luckily, it had already been cut and we saw the damage in a narrow strip where the cutter missed. You can see what the damage looks like in the picture above. The top 2 blades of grass on the stem turn completely brown. When you see this over a whole field, those brown blades at the top will give the grass a “frosted” appearance.
Here’s another shot of the damage from Bermudagrass Stem Maggot.
Here is some control information from Dennis Hancock and Will Hudson, UGA Forage Specialists:
Harvest management is an option for mitigating the damage caused by bermudagrass stem maggot. If damage is found within 1 week of the normal harvest stage, proceed to harvest the crop as soon as weather conditions allow. Once the damage becomes apparent, the crop is unlikely to add a significant amount of yield. If damage is observed within 1 to 3 weeks after the previous harvest, it is also likely that the crop will not add a significant amount of yield. The damaged crop should be cut and (if the yields are substantial enough to warrant) baled and removed from the field as soon as weather conditions allow. Leaving the damaged crop in the field will only compete with any attempts by the plant to regrow and decrease the opportunity that the next cutting will have to accumulate mass.
Control of bermudagrass stem maggot can also be achieved through the foliar application of relatively inexpensive insecticides. Current recommendations are to treat after a cutting if damage levels are high. Best results have come from treating twice, once a few days after baling the previous crop as the grass begins to resprout, and again 5-7 days later. The lowest labeled rate of any pyrethroid insecticide that is approved for hayfield application has been effective. No differences have been noted among the brands or active ingredients. There is no residual activity with these insecticides beyond a few days after application but the infestation levels that cause concern usually build later in the season. So far a single round of treatments has lasted through the rest of the growing season. Considerable reduction in damage can be seen after a single application as the grass regrows, and for late season that may be a more cost-effective option.