Maize Silk pH as an Indicator of Resistance to the Corn Earworm (Lepidoptera: Noctuidae)

To investigate whether the pH of maize, Zea mays (L.), silks could serve as a useful screening criterion for resistance to the corn earworm, Heliothis zea (Boddie), the relationship between silk pH of six maize genotypes and damage resulting from artificial infestation of ears with corn earworm larvae was determined. Higher mean pH values generally corresponded to reduced corn earworm damage. Silk pH of all entries increased as silks matured. When silk pH and corn earworm damage were determined in four cycles of selection of a maize population which had undergone recurrent selection for corn earworm resistance, a significant linear relationship between pH and cycle of selection was observed. Significant correlations were observed between silk pH and corn earworm damage and between the percentage of plants with nonbrowning silks and corn earworm damage. There appears to be only limited potential for using silk pH or the nonbrowning silk trait as the sole screening criterion for corn earworm resistance, but when combined with other criteria, they will contribute to increased corn earworm resistance screening sensitivity.