Ag Weather Forum

The U.S. livestock industry is on the watch -- and then some -- over the threat of the New World screwworm and its potential to migrate from Mexico north into Texas. Projects have been approved and millions of dollars in funding allocated to control this parasite and keep it from spreading if it appears in Texas.

One detail that will be closely tracked as we move closer to the end of the year and toward winter is the temperature forecast for the southern United States, specifically Texas. The reason for this detail is the parasite dies out in even chilly weather. A fact sheet on New World screwworm by Kansas State University in June 2025 summarizes the temperature scenario for the parasite this way:

"The New World screwworm is not tolerant of cold weather. Adults do not survive air temperatures below 20 degrees Fahrenheit. Larvae dropping from the host between 15 to 20 degrees Fahrenheit usually die. Pupation does not occur in dry soil when the mean average daily temperature is below 46 degrees Fahrenheit."

However, the DTN winter 2025-26 outlook indicates temperatures in the southern U.S., specifically in Texas, are not likely to drop to the threatening cold level for the New World screwworm. Temperatures throughout the southern U.S. are forecast to be from 1-2 degrees Fahrenheit above normal. The normal overnight lows during the meteorological winter months of December, January and February range from the mid-40s to mid-50s Fahrenheit in southern Texas. So, the forecast gives a notable suggestion that conditions would not be life-threatening to any NWS flies or larvae, should they manage to enter Texas or any other southern state.

Of course, a re-occurrence of the bitter 10-day cold wave that spread across Texas back in 2021 could certainly hinder any NWS larvae survivability. The NOAA National Centers for Environmental Information (NCEI) noted the cold wave covered the entire state during the Feb. 11-20 period. "Every county in the state as far south as the Rio Grande River and northeastern Mexico was placed under a Winter Storm Warning, with many experiencing wind chill values below zero," the NCEI summary of the Great Texas Freeze said. Such temperatures would be well below the New World screwworm survival threshold of 45 F.

At this time, however, the forecast indicates temperatures will track toward being favorable for New World screwworm survivability, should the parasite show up north of the U.S.-Mexico border.

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Want to know more about the winter ahead? Join DTN's Winter Weather Webinar on Wednesday, Oct. 22 at 11 a.m. CDT. You can sign up for free here: https://www.dtn.com/….

More DTN coverage of the New World screwworm threat is available here: https://www.dtnpf.com/….

Bryce Anderson can be reached at bryce.anderson@dtn.com

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