WASHINGTON, D.C.: President Donald Trump’s administration warned over the weekend that it might limit livestock imports from Mexico if Mexico doesn’t do more to fight a dangerous pest called the New World screwworm.

U.S. Agriculture Secretary Brooke Rollins sent a letter to her Mexican counterpart, saying she would block animal imports if the problem is not fixed by April 30. Rollins posted the letter on the social media site X.

She said Mexico has only allowed planes to spray for the past six days a week and has added heavy taxes on airplane parts needed for the spraying.

This warning comes as the U.S. is already in a global trade fight, with Trump raising tariffs on Mexico and other countries.

Screwworms are harmful insects that can infect livestock, wildlife, and sometimes people. Their larvae burrow into the skin of living animals, often causing serious or deadly injuries.

Before the pest was found, Mexico was the U.S.’s biggest cattle supplier. Last month, the U.S. imported 24,000 cattle from Mexico, down from about 114,000 a year earlier.

The U.S. had stopped Mexican livestock shipments in November when the screwworm was discovered but allowed them again in February under new health rules.

Fox News was the first to report on Rollins’ letter.