Sometimes the burs are called field sandburs, Southern sandbur or simply sandbur.
From the chron.com
One such eradication was that of sandbur, Cencrus echinatus, an introduced grass on Laysan.
From the en.wikipedia.org
More examples
Grass of the eastern United States and tropical America having spikelets enclosed in prickly burs
Cenchrus is a genus of about 25 species of grasses in the family Poaceae. Common names include buffelgrasses, sandburs, and sand spur. Some botanists include the genus within the related genus Pennisetum.