18 NEBRASKA CATTLEMAN October 2026 N W S PAIGE HEREL | NEBRASKA DEPARTMENT OF AGRICULTURE In June 2026, the rst U.S. case of New World screwworm (NWS) was detected in a 3-week-old calf in Texas. This detection comes after a year of close monitoring across the border in Mexico as well as the release of sterile ies to mitigate the harsh impact of this pest. NWS is a pest that can cause extensive damage to livestock. NWS ies lay their eggs in wounds or small cuts as well as the umbilical area in young calves. The larvae then burrow (like a screw) into the living esh, typically causing serious and potentially deadly damage. Adult screwworm ies are about the size of a common house y, with orange eyes and a metallic blue or green body and three dark stripes along their back. NWS infestations are most common in livestock, pets, wildlife and occasionally birds, but is rarely found in people. The entire life cycle of NWS can be as fast as 21 days. After the female y – which mates only once in her lifetime – is fertilized, she searches for open wounds or ori ces on a host, then lays her eggs. After 12 to 24 hours, the eggs hatch and the larvae take ve to seven days to grow. During this time, they tear into their host’s esh, feeding until they are fully developed. When they are ready, the larvae drop from the host and bury themselves in the ground to pupate. This is where they will transition into pupae for six to eight days before emerging as an adult y and starting the cycle over again. NWS has been found in the United States since 1842 and previously posed a serious threat. In 1957, the U.S. Department of Agriculture (USDA) started an eradication program after the development of the sterile insect technique in the 1940s. NWS was originally eradicated in 1966. In 2016, this technique was also used in a small outbreak in Florida, eradicating it by March of 2017. The sterile insect technique involves releasing sterile male ies into the a ected region. These males mate with females that then lay unfertilized eggs. As the adult ies die o , there aren’t any to replace them and, eventually, the species dies o altogether in that region. The bene ts of this technique include not using chemical pesticides and it poses no risk to humans, livestock or pets. USDA is working diligently to keep this pest at bay. Part of their long-term response involves several di erent investments. One of the most recent being $25 million put toward the opening of a new sterile- y-dispersal facility in Arizonia. Additional investments include modi cations to the Metapa, Mexico fruit y facility to produce sterile NWS male ies, as well as the construction of another sterile y production facility at Moore Airbase in Edinburg, Texas. While NWS is a signi cant concern to the United States and the livestock industry, NWS has historically not established itself this far north. Nebraska has the advantage of winter weather that will kill the y. The adult y will decrease activity when temperatures fall below 70 degrees, and the pupae will die in the soil before transforming into a y when the temperature drops below 42 degrees. Prevention begins with inspection, protection and treatment. It’s important to inspect livestock PRODUCTION Graphic courtesy of USDA.
RkJQdWJsaXNoZXIy NTMxNTA5