Substantial rains, like those much of the state has recently had from hurricanes and tropical storms, often trigger armyworm outbreaks. The perception that armyworms are worse this year is probably because dry weather seems to inhibit their reproduction. Farmers are delaying wheat planting to avoid the pests.
Intense armyworm infestations continue to consume pastures and hay meadows, but there's no indication that population counts are any larger than in previous years, according to a Texas AgriLife Extension Service expert.
"I don't think they're worse, but it's probably more intense (sudden) onset," said Dr. Allen Knutson, AgriLife Extension entomologist.
Substantial rains, like those much of the state has recently had from hurricanes and tropical storms, often trigger armyworm outbreaks, he said. The perception that armyworms are worse this year is probably because dry weather seems to inhibit their reproduction.
"There was a long period of time when it was dry and there was no armyworm activity. Then all of sudden, here they are in large numbers," he said.
Knutson said no one really knows why armyworms burst forth in large numbers when it rains following a dry period. But the theory is that eggs and small larvae survive when the humidity is high and plant growth is lush.
"We know the (armyworm) moths are moving up from South Texas all summer long and no doubt laying eggs, but the eggs and small larvae just don't survive when it's hot and dry," he said.
Now that conditions are ripe for their survival, armyworms will be active and require spraying until the first cold weather comes in, Knutson said.
"It'll take a freeze to actually kill them because they're not cold-tolerant, but certainly cooler weather will slow their development," he said. "We still are weeks and weeks away from that, so there's lots of time for armyworms to do damage. It's too early to hope that weather is going to slow down the infestations."
Armyworms are not only damaging existing pastures, they are also delaying planting wheat for grazing and small grains for winter pastures, according to AgriLife Extension agent reports.
Armyworms can strip a field of newly emerged small grains overnight, Knutson said.
"Wheat producers are considering sowing early for grazing, but most are worried about armyworms," said Steven Sparkman, AgriLife Extension agent for Hardeman County, west of Wichita Falls. "I think it is unsafe to sow at this time."
"Some producers have begun sowing wheat, but most are holding off another week or two due to reports of armyworms to the north, especially in Oklahoma," said Heath Lusty, AgriLife Extension agent for Jack County, northwest of Fort Worth.
"What the armyworms hadn't gotten last week, they are getting this week," said Josh Blanek, AgriLife Extension agent for Somervell County, south of Dallas. "But if the armyworms aren't eating your grass, you're probably in pretty good shape after the good rains."