Grain Sorghum Yield and Susceptibility to Insects as Affected by Early Season Growth

Abstract

AbstractVigorous and uniform seedling emergence and growth are considered essential for profitable crop production. The objective of this note is to document the effect of nonuniform growth, apparently caused by differences in planting depth, on the susceptibility of grain sorghum [Sorghum bicolor, (L.) Moench] to Heliothis zea (Boddie) in a production environment. Observations were made within an 8‐ha field near Florence, SC, where differences in productivity among 17 soil map units representing seven soil series classified as Ultisols were being determined. The center two rows of each six‐row planting configuration grew more slowly than and reached the boot and bloom growth stage approximately 7 to 10 d after the outside rows. During early grainfill this delayed growth and development resulted in more than 90% infestation of the center rows by Heliothis zea compared with less than 10% infestation in the outside rows. Differential growth and subsequent Heliothis damage to the crop were similar across all soil map units. Average grain yield was reduced from 3110 to 1640 kg ha−1, apparently because deeper seed placement slowed plant growth and development enough that there was subsequent synchronization between a third generation Heliothis flight and flowering. This demonstrates that nonuniform plant growth and seasonal insect populations can reduce yield by nearly 50% in the Southeastern Coastal Plains.