Southwestern corn borer growth on laboratory diets containing lyophilized corn husks

Southwestern corn borer (Diatraea grandiosella Dyar) is a serious pest of corn (Zea mays L.) in the southern USA, Lack of reliable techniques for evaluating resistance after anthesis is a major problem. The objective was to develop a laboratory bioassay for evaluating southwestern corn borer larval growth on diets comprised primarily of lyophilized husks of corn inbred lines, Diets were prepared by adding 15 g of lyophilized husk tissue collected within 3 d after silk emergence to a mixture of 250 mL distilled water, 2400 mg agar, 12.5 mg gentamicin sulfate, 132 mg sorbic acid, and 528 mg ascorbic acid. Larvae were weighed after feeding on the test diet for 21 d. Larvae fed diets containing husks of different inbred lines varied significantly. Because southwestern corn borer larvae that infest corn plants at or after anthesis feed initially on husks, this bioassay is a potentially useful technique for identifying resistant germplasm.