Corn Hybrids for Late Planting in the Southeast

Abstract

Delayed planting dates in the U.S. Southeast often result in insect and disease problems on corn (Zea mays L.). The objectives of this study were to determine the effects of corn hybrid (type) and planting date on yields and the extent of injury resulting from insects and pathogens. Tropical, Bt (Bacillus thuringiensis var. kurstaki Berliner), and non‐Bt corn hybrids were evaluated for grain and silage yields and insect damage at planting dates from March to August from 1998 to 2001. Averaged across years, corn silage yields were greatest at March and April planting dates (16.1 Mg ha−1) and least from July (6.1 Mg ha−1) and August (4.5 Mg ha−1) planting dates. Silage yields of tropical corn were 26 and 17% higher than non‐Bt and Bt hybrids, respectively, because of less yield reduction at later planting dates. Corn grain yields were greatest at the March planting date (9.6 Mg ha−1) and least at July and August planting dates (0.9 and 0.4 Mg ha−1, respectively). Grain yields of tropical corn were 15 and 10% higher than those of Bt and non‐Bt, respectively. Fall armyworm (Spodoptera frugiperda J.E. Smith), corn earworm (Helicoverpa zea Boddie), and southern corn rust disease (Puccinia polysora Underw.) ratings had negative correlations with corn yields. Insect damage was below 6% for Bt hybrids and above 11% for non‐Bt hybrids. Tropical corn had higher silage and grain yields and better silage quality and disease resistance than either Bt or non‐Bt hybrids.