By Cassandra Garrison TAPACHULA, Mexico (Reuters) -On a scorching afternoon in the rural heartland outside Mexico's southern city of Tapachula near the Guatemala border, rancher Julio Herrera calls his herd back from an afternoon of grazing.

(Reuters) -The U.S. Department of Agriculture will spend up to $750 million to build a facility in Texas that produces sterile flies to fight the flesh-eating livestock pest New World screwworm, Secretary Brooke Rollins said on Friday.

Mounted patrol officers, known as tick riders, who typically patrol the southern border to protect cattle from fever tick, will also now serve as the first line of defense against screwworm.