What are Urons?

I was reading a tech manual today, and came across the chemical group called "Urons".

What are Urons?

Urons is an abbreviations of Phenylurea herbicides: 

"Substituted phenylurea herbicides are a group of pesticides used for general weed control in agricultural and nonagricultural practices – for example, along railroads, utilities' rights-of-way, and in industrial areas."

Boom. 

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