The bermudagrass stem maggot (Atherigona reversura), a pest of bermudagrass forage in Texas has been reported in multiple counties since 2012. The bermudagrass stem maggot is native to south Asia (from Japan westward to Pakistan) and was first reported in the United States in Georgia in 2010. This pest only infests bermudagrass and stargrass (Cynodon spp.). The fly (yellow with black head) lays its eggs within the stem of the bermudagrass plant. Once the egg hatches the larva, or maggot, (white with black head, 1/8” – 3/16” long) moves to the last plant node and consumes the plant material within the stem. This stem damage results in the death of the top two to three leaves while the rest of the plant remains green. This gives a stand of bermudagrass the appearance of frost damage. The amount of damage seems to be dependent on growing conditions as well as the point during regrowth when the flies lay their eggs. If there are good growing conditions with good soil fertility and moisture the loss seems to have minimal impact on dry matter yield. However, if forage production is limited by poor soil fertility and dry soil conditions more damage can result. The shoot stops elongating as a result of the insects damage. In response the plant may grow another shoot from a lower node of the damaged shoot. This new shoot can also be attacked by later generations of the bermudagrass stem maggot.
Most producers will typically see the resulting damage before finding the pest. Producers are less likely to see damage in a grazing pasture since livestock will keep forage grazed down.
Management recommendations for hay meadow damage are to harvest hay as soon as possible to reduce the yield impact. 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 a harvest, it is also likely that the crop will not add a significant amount of yield. The damaged crop should be cut and 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 dry matter.
A foliar application of any pyrethroid (beta-cyfluthrin, cyfluthrin, lambda-cyhalothrin and zeta cypermethrin) insecticide labeled for bermudagrass can control the bermudagrass stem maggot. However, guidelines on the economic return on controlling this new pest and timing of and frequency of insecticide treatments have not been clearly defined.
Vanessa Corriher-Olson, Forage Extension Specialist, Soil & Crop Sciences, Overton, TX
Texas A&M AgriLife Extension Service, Texas A&M University System