“…European corn borers can be reared on a meridic diet for 1 to 14 generations without loss in virulence; virulence starts to break down by the 17th generation and by the 34th genera tion, larval survival is so low on field corn that relative resistance ratings of corn genotypes can not be made (Huggans and Guthrie, 1970;Guthrie and Carter, 1972;Guthrie et al, 1974;Rathore and Guthrie, 1973).…”