Forage producers around the state are battling fall armyworms and taking protective measures to defend high value pastures and fields for hay and grazing, according to Texas A&M AgriLife Extension Service experts.
David Kerns, Ph.D., AgriLife Extension’s statewide integrated pest management coordinator and associate department head for the Texas A&M Department of Entomology, said he’s seen reports about spotty outbreaks of fall armyworms in parts of Texas earlier than usual. He said the localized nature of those infestations in rice fields and improved pastures like Bermuda grass suggests environmental conditions were right for populations to flare up.
When it comes to armyworms, Kerns said every year is different, but population spikes and the potential for infestations are directly linked to rainfall.
“Outbreaks are always tied to precipitation,” he said. “Wet weather during the summer promotes grass growth in the landscape, and healthy pastures provide habitat for their populations to build.”
In recent weeks, however, AgriLife Extension agents in counties around the state have reported fall armyworms in standing pasture, early winter wheat fields and landscapes. Forage and cattle producers are monitoring their numbers closely or initiating control regimens.
Damage to standing forages and emerging wheat has been reported from North and East Texas to the Coastal Bend and the South Plains regions.
Fall armyworms on the march
Fall armyworms are extremely damaging to forages and got their name because they appear to march army-like across hay fields, consuming the grass in their path.
Vanessa Corriher-Olson, Ph.D., AgriLife Extension forage specialist in the Texas A&M Department of Soil and Crop Sciences, Overton, said she has been busier than usual fielding calls and holding presentations for producers at the request of AgriLife Extension agents who are receiving calls. She highly recommends producers who value forages to be on alert and prepared to initiate control regimens.
Fall armyworms are green with brown or black colorations and can be identified by the white inverted Y on their head. They can grow up to 1.5 inches in length when mature.
Fall armyworm moths can lay up to 2,000 eggs that hatch in two to three days, according to a 2021 report, “Fall Armyworm Control in Pastures (PDF),” by AgriLife Extension entomologists.
The pest’s name is also indicative of its active season, and activity typically begins to increase between July and September, Kerns said. The pest can persist until frost.
Whether producers hope to make one more cutting of warm-season hay or establish good stands of cool-season forages like ryegrass or winter wheat, Corriher-Olson said they should be ready to act against fall armyworms as soon as the pests near threshold.
She recommends producers scout for fall armyworms in the morning.
Armyworm presence may be evident in emerging winter forages, but in taller forage canopies. Kerns recommends using a canvas drag net to sweep through the standing grass in multiple locations in each field or pasture.
“Scouting for armyworms should be a part of your daily routine, especially if you have standing forage that you will be relying on for winter feeding and grazing,” Corriher-Olson said.
Be on the lookout, stay prepared
Corriher-Olson said some forages may need more attention than others.
“There is a lot of overseeding to be done and young winter wheat and ryegrass out there now,” she said. “Those seedling annuals are much more sensitive to fall armyworm damage than our warm-season perennials. If Bermuda grass is eaten, it can bounce back, but if those fledgling winter annuals that are a few inches tall are eaten back to the root before they’re well-established, you’re likely going to need to replant.”
Producers with high-value irrigated forages should consider fall armyworms a constant threat because the consistent moisture creates the right conditions for population booms, Corriher-Olson said.
Kerns said pyrethroid-based pesticide applications are typically the go-to control method because they are low cost, but they are not 100% effective, especially when armyworm populations are high. Pyrethroids don’t last long on the crop they protect, and rain can wash the spray away.
For longer residual control he recommends a mix of pyrethroid and products with the active ingredient diflubenzuron or chlorantraniliprole. Diflubenzuron will not work on bigger worms, but its residual sticks around and will knock back younger caterpillars and hatchlings. Products with chlorantraniliprole offer long residual control of all sizes of worms and is rainfast. Other products containing methoxyfenozide will provide moderate residual control but are susceptible to washing off during rainfall.
“Mixing products is just a good strategy, especially under high pressure,” Kerns said. “That may also be a good strategy to defend early stands of winter wheat and ryegrass between now and the first frost.”
Panhandle
The weather was hot, dry and windy. Harvest of feed grain and forage crops continued. Most cotton fields had reached 65% or more open bolls, and some growers started applying harvest aids to expedite harvest. Others were allowing more time for maturity of upper canopy bolls. Emergence of early planted small grain crops appeared to be making good progress with expanding leaf width and length dimensions contributing to canopy that was quickly filling space between seed rows. Improvements in soil moisture would help germination and emergence. Rangeland and pastures were going dormant. Overall soil moisture was very short to adequate. Pasture and range conditions were very poor to fair, and crop conditions were poor to good.
