Here are the 1950 recommendations for controlling second-brood corn borers and the results of second brood borer control studies in 1948 and 1949.
Blickenstaff, C. C. and Fronk, W. D.
"Watch Out For Second Brood Borers,"
Iowa Farm Science: Vol. 5
, Article 2.
Available at: https://lib.dr.iastate.edu/farmscience/vol5/iss2/2