A new pest, the bermudagrass stem maggot, has been detected in seven Texas counties in the Gulf coast region and a pair of entomologists with Texas AgriLife Extension are warning forage producers to be aware of the dangers the pest presents to growers.
Robert Bowling, Texas AgriLife Assistant professor and Extension specialist in Corpus Christi, reports the Bermudagrass stem maggot, Atherigona reversur, is native to several Asian countries. In 2010, it was reported damaging bermudagrass from three counties in Georgia. This invasive fly quickly spread across the southern U.S. and, in 2013, was first reported infesting bermudagrass in Texas.
"The adult BSM is a small yellowish fly with dark eyes. It lays eggs on the bermudagrass stem near a node. The immature (maggot or larva) stage is yellowish and grows to about one-eight-inch long," Dr. Bowling noted in a South Texas entomology update earlier this month. "Larvae are generally hard to find because they frequently have left the stem by the time plants show symptoms of damage."
Pest specialists note there are multiple generations of BSM each summer, so scouting regularly for the maggots can help management and control efforts.. Bowling says the BSM lifecycle lasts about 3 weeks, but it could be as short as 12 days.
"It is the immature BSM that is responsible for damage to bermudagrass. The larva will work its way toward a node shortly after hatching from the egg. As the larva develops it will burrow in the shoot and begins feeding, causing leaves above the feeding site to wither and die," he warns.
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Bermudagrass damaged by BSM will have a frosted appearance. Shoot elongation stops as a result of the insect’s feeding. The plant may grow another shoot from a lower node of the damaged shoot. However, the new shoot can be attacked by later generations of the bermudagrass stem maggot.
Jason Ott, Texas AgriLife Extension agent in Nueces County, reports BSM have been detected in Lavaca, Waller, and five other Texas counties so far this year. He says bermudagrass damaged by BSM will have a frosted appearance.
"Early harvest is suggested when infested fields are within seven days of the normal harvest stage. Heavily infested fields should be harvested earlier. Baled grass should be removed from the field to limit subsequent infestations of BSM," Ott warned forage growers in a bulletin issued this week.
"Although all bermudagrass varieties are reported to be susceptible to BSM, coarse stemmed varieties often have fewer affected stems. Research from Georgia and Japan suggests thicker-stemmed varieties such as Tifton 85, Coastcross-I, Tifton 68, and others, have fewer stems affected by the damage as a proportion of the number of stems per unit area when compared with finer textured varieties."
Bowling indicates infestations are usually worse in late summer. The severity of damage to bermudagrass often is dependent on the point during regrowth when the flies lay their eggs. Conditions favoring rapid pasture growth rates, i.e. good soil and moisture conditions, may delay damage and loss of the last one to three leaves seem to have a minimal impact on yield. Conversely, producers have reported major yield losses during poor growing conditions.
Infested fields should be treated with a foliar-applied insecticide within a few days following harvest. A second application may be warranted in cases of severe infestations. Relatively low rates of pyrethroid insecticides should provide effective control of adults helping to limit reinfestation. Read and follow label directions carefully as pre-harvest intervals will differ among pyrethroid insecticides.
For more information about BSM in bermudagrass and possible reports of infestations in your county, contact your county agent of the nearest Texas AgriLife research station in your area.