Evaluating maize for allelochemicals that affect European corn borer (Lepidoptera: Crambidae) larval development

European corn borer (ECB), Ostrinia nubilalis (Hubner), larvae develop resistance to management protocols in laboratory and field environments. Laboratory bioassays, tissue elemental analyses, and field resistance evaluations were conducted on ear tissues of maize, Zea mays L., to (i) identify genotypes and tissues which affect ECB development, (ii) isolate tissue extracts detrimentally affecting larvae, (iii) determine if high performance liquid chromatography (HPLC) absorption peaks are associated with biological activity, (iv) determine if ferulic acid and p-coumaric acid affect ECB larvae, and (v) determine if laboratory and field resistance are related. Tissue and genotype did not affect larval survival. Silk tissue from W182E, 'Apache', MN 3153, and MN 276 reduced 10-d larval weight, increased time to pupation, reduced pupal weight, and increased time to moth emergence compared with kernel tissue, which did not differ from the cellulose control. Methanol fractions of silks reduced 10-d larval weight, but not larval survival, compared with the cellulose control. No methanol fraction of silks, except from MG 15, reduced 10-d larval weight as much as nonextracted Apache silk, suggesting that some allelochemicals were not captured or were lost during extraction. HPLC analysis detected three to four large peaks only found in active methanol fractions. Ear tissue element levels, except for manganese (r = -0.70), were not associated with decreased 10-d larval weight. Larvae reared on diet containing ferulic acid (2.61 and 1.67 mg/g) or p-coumaric acid (<0.20 mg/g) had 10-d weights similar to the control. Laboratory and field resistance were not correlated, suggesting that multiple resistance mechanisms exist in maize. The identification of allelochemicals affecting ECB larvae will allow breeding programs to select resistant maize genotypes.