Evaluation of Germplasm Lines of Maize for Resistance to Fall Armyworm1 and Southwestern Corn Borer2 Leaf-Feeding Damage

Maize (Zea mays L.) is an economically important crop with worldwide production of 1,162 billion tons in 2020. Larvae of fall armyworm, Spodoptera frugiperda (J.E. Smith), attack all above-ground parts of maize plants from the seedling stage to maturity, while southwestern corn borer, Diatraea grandiosella Dyar, feed in plant whorls, on developing ears, and tunnel in stalks. The objective of this study was to evaluate germplasm lines developed by USDA-ARS but not released, for leaf-feeding damage by fall armyworm and southwestern corn borer and compare damage to maize lines previously released. The maize lines were planted in replicated experiments in the field. Plants were artificially infested at the whorl stage of growth, and leaf-feeding damage by fall armyworm or southwestern corn borer neonates was evaluated 14 days after infestation. Leaf-feeding damage scores differed significantly among the lines for both insect species in 2020 and 2021. From the 13 non-released "Mp" lines evaluated, damage scores for combined years ranged from 2.37 (Mp97:155) to 3.14 (Mp68:616) for fall armyworm and 3.42 (Mp97:155) to 4.64 (Mp97:161) for southwestern corn borer. Non-released "Mp" lines had better than moderate resistance to leaf damage by fall armyworm and moderate resistance to southwestern corn borer. The lines could be useful for producing breeding crosses with other resistant lines or with lines that have other desirable traits.