Mutants are viable, but may be distinguished from normal plants by FeCl staining: plants able to synthesize benzoxinoids have pale blue color when crushed and treated with FeCl solutions (Hamilton 1964, Simcox 1993 ). Mutations in the bx1 gene reduce the resistance to first generation European corn borer (Ostrinia nubilalis) that is conferred by benzoxazinoids (Klun et al. 1970 ). Bx1 mutant maize deposited less callose in response to chitosan elicitation than isogenic wildtype plants (Ahmad et al. 2011 ). Genetic mapping using recombinant inbred lines derived from maize inbred lines B73 and Mo17 showed that a 3.9 kb cis-regulatory element that is located approximately 140 kb upstream of Bx1 causes higher 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) accumulation in Mo17 than in B73 seedlings (Zheng et al. 2015 ). This genetic variation is also associated with higher corn leaf aphid (Rhopalosiphum maidis) reproduction on B73 compared to Mo17 maize seedlings (Betsiashvili et al. 2014 ). Relative to maize inbred line W22, Bx1::Ds mutant maize plants are more sensitive to corn leaf aphids (Rhopalosiphum maidis)  (Betsiashvili et al. 2014) and beet armyworms (Spodoptera exigua) (Tzin et al. 2017 ). Highly localized induction of benzoxazinoid accumulation in response to Egyptian cotton leafworm (Spodoptera littoralis) feeding is abolished in a maize bx1 mutant (Maag et al. 2016 ).