They are using arsenic filled pesticides, like we once used in the USA (may be different products but same results).
Leach and Lipp reported the first arsenical crabgrass control
using lead arsenate in 1927. He further reported the Ohio Agricultural Experiment Station performed extensive studies using arsenates for crabgrass control from 1930 to 1947; reporting crabgrass control from one application of lead arsenate, 35 pounds per 1000 square feet, lasted 10 years.
An article in a 1950 Denver Post recommends mixing five pounds of arsenate of lead with two cubic feet of sand and scattering it over the infested area to eliminate "night crawlers" (Partridge, 1950). In 1953 a Denver Post advertisement indicates arsenate of lead kills crabgrass and nightcrawlers, and can be mixed with fertilizer.
Interestingly enough, rice from India is high in lead and arsenic. https://www.consumerreports.org/cro/magazine/2015/01/how-much-arsenic-is-in-your-rice/index.htm
They are using arsenic filled pesticides, like we once used in the USA (may be different products but same results).
http://www.aaem.pl/pdf-74715-12551?filename=The%20history%20of%20arsenical.pdf