Laboratory Bioassay for Resistance in Corn to Fall Armyworm (Lepidoptera: Noctuidae) and Southwestern Corn Borer (Lepidoptera: Pyralidae)

Abstract

Inbred lines of corn, Zea mays L., were evaluated for resistance to leaf feeding by the fall armyworm, Spodoptera frugiperda (J. E. Smith), and southwestern corn borer, Diatraea grandiosella Dyar, in field and laboratory experiments. For the laboratory bioassays, diets were prepared from lyophilized whorl tissue of field grown plants of resistant and susceptible corn inbred lines. To prepare the diets, 11 g lyophilized tissue was stirred into a mixture of 250 ml distilled water, 2 g agar, 12.5 mg gentamicin sulfate, 132 mg sorbic, and 528 mg ascorbic acid that had been heated to 82°C and poured into 30-ml plastic cups. Cups were infested with two neonate larvae each. Fall armyworm larvae reared for 10 d on diets containing tissue of resistant inbred lines weighed 60% less than those reared on diets containing susceptible inbred tissue. Southwestern corn borer larvae reared for 14 d on whorl tissue from resistant inbred lines weighed 50% less than those reared on susceptible tissue. The laboratory bioassay satisfactorily differentiated among resistant and susceptible corn inbreds.