Spraying to control weed and insect pests has grown from babyhood to manhood in about 5 years. Chemical sprays are the "ace in the hole" a farmer has at his disposal.
Gunderson, Harold and Sylwester, E, P.
"Spraying Grows Up,"
Iowa Farm Science: Vol. 5
, Article 8.
Available at: https://lib.dr.iastate.edu/farmscience/vol5/iss12/8