"So, if you don't find them when they are still really tiny, by the time you get to them with a sprayer, they've already done the damage," Kesheimer said. While the caterpillars feed for up to two weeks, they do their worst, most damaging work rapidly in their last few days as caterpillars. "Another good thing to do is go out in the morning when it's still wet and walk through a field, and if you get worms on your boots, think about treating that field," Kesheimer added. That's why entomologists recommend scouting early in the morning or just after dusk, preferably with a sweep net. In the heat of the day, they also huddle near the thatch layer - where grass meets the ground - and only venture out to eat the top of plants when it's cooler. Part of the problem is that armyworms start off incredibly small, with the initial instars measuring less than one sixteenth of an inch, Kesheimer explained. "Growers can look at a field on Friday, and it looks fantastic, and by Sunday, it's completely gone," Kesheimer said. "That helped them expand their range and move farther and farther," Kesheimer said.Ĭommon to this year's armyworm damage were farmers who were stunned by the insect's rapid devastation, which can occur seemingly overnight. shores - just as armyworms were reaching epidemic levels in the South. Things quieted in July, but August brought five storms to U.S. "Two - Claudette and Elsa - had long tracks through the U.S.," Baranick noted. One storm developed in May, with four making landfall throughout June. "This year, we saw a bunch of tropical storms form early on," he added. The country has seen 20 named storms, with seven hurricanes this season, above the yearly average, Baranick noted. "Since adults are migratory, they are flying north, but they also use winds and storms to move around," Kesheimer explained. Throw in an active tropical storm and hurricane season, and the stage was set for armyworms to wreak havoc across a broad geographic range. "They feed faster, they reproduce faster and their life cycle shortens a little," she said. Like all insects, armyworms are cold-blooded, which means they are more active in warmer weather, Kesheimer noted. Starting in June, much of the U.S, especially the northern and western regions, saw above-average temperatures, with the country clocking its hottest summer on record overall this year. "So, we can have five to seven generations in a single season, if the weather is right," Kesheimer said of Alabama growers.Ī hot summer probably didn't help, added DTN Ag Meteorologist John Baranick. Armyworms are blessed with a rapid generation turnover - they can lay eggs, hatch, feed, mature, mate and lay eggs again in a matter of weeks. "We had a warm winter across the South, so more of them survived and got off to an early start, so we started the year with higher numbers," she said. Normally it overwinters in South America or the southernmost regions of Texas and Florida, and adult moths must slowly make their way north each spring, Kesheimer explained. That's unusually early for the insect, which cannot tolerate cold winters. The first red flags of the season were the armyworms spotted in the Midsouth as early as May, eating their way through pastures and hay fields. Growers would do well to invest in a sweep net, get up to speed on local moth monitoring networks and study the identification and management of this pest for next season, she said. "But if you look at what those storm components were - a warm winter, lots of tropical storm systems and potential spray failures - those are going to become more common moving forward and chances are that they will line up again before the next 50 years. "We had the perfect storm of events that led to this snowballing effect that let them take over the entire country," Kesheimer said. This year's fall armyworm epidemic - the worst in nearly five decades by some entomologists' estimates - may be ending, but this level of armyworm infestation could happen more frequently in the years to come, warned Auburn University Extension Entomologist Katelyn Kesheimer. (DTN) - October holds the promise of cold weather, first frosts and, for many, the blessed end of the march of the fall armyworms, a season-long invasion that plagued farmers, ranchers and homeowners across the country this year.īut don't let that welcome chill comfort you too long. (Photo courtesy Katelyn Kesheimer, Auburn University) Here's why it happened and why it could happen again soon. A sweep net filled with fall armyworms was a common sight this year, after the worst armyworm epidemic in decades plagued grain farmers, forage growers and homeowners around the country.
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