Natural resistance of native and commercial maize to fall armyworm, Spodoptera frugiperda, and corn earworm, Helicoverpa zea, and their relationship with ear rot.
Maize (Zea mays L.) is the most representative crop of Mexico, mainly because of its social, cultural, and economic importance. The objective of this research was to identify genotypes with natural resistance to damage by fall armyworm, Spodoptera frugiperda (J.E. Smith), and corn earworm, Helicoverpa zea (Boddie), and their relationship with ear rot caused by Fusarium spp. Link (Nectriaceae). Samples were collected from September to November 2019 from hybrids and native maize in nine plots in Puebla and Morelos states. Ear rot pathogens and Lepidoptera found in plots were morphologically identified; ear rot incidence, severity, and damage caused by the pests were evaluated. Data of ear rot, leaf damage, and ear damage were adjusted by arcsine square root and analysis of variance (ANOVA), and means were compared by a Tukey multiple range test (p = 0.05). Fusarium spp. was found with 15.04 to 32.01% severity; damage by fall armyworm and corn earworm ranged from 23.63 to 46.96%, with galleries as long as 4.77 cm. The amount of ear rot was proportional to damage by Lepidoptera, demonstrating relationship between injury by these insects and ear rot severity caused by Fusarium spp. in hybrids and native cultivars in different areas, cultural practices, and production systems. Genotypes more resistant to damage by pests were Black Native from San Miguel, Teotlalco, Puebla; Pioneer 30F35 from Contla, Puebla; Pioneer P4028W from Tetelilla, Morelos; and Pioneer P4028W from Tepalcingo, Morelos.