Influence of a Disease Complex on Yield and Quality Components of Silage Corn 1

In 1969 severe leaf blighting was observed in hybrid corn (Zea mays L.) trials. This blight was attributed to Phyllosticta sp. and was accompanied in later stages by both stalk rots [Diplodia zeae (Schw.) Lev. and Gibberella zeae (Schw.) Fetch] and European corn borers (Ostrinia nubilalis Hubner). In 1970 corn hybrids were affected by southern corn leaf blight (Helminthosporium maydis Nisik. and Miyake). Paired samples of diseased and relatively nondiseased plants were taken in both years, were fractionated, and were evaluated for quality components. The Phyllosticta sp.-stalk rot disease complex reduced dry matter yields, while both percent cell wall constituents (CWC) and acid detergent fiber (ADF) were significantly higher — and therefore cell solubles correspondingly lower in the diseased fractions compared to the nondiseased fractions. Similarly, nitrate-N (NO₃-N) levels were significantly higher in the diseased fractions compared to the nondiseased fractions. When all fractions were compared, there was no significant difference between diseased and nondiseased samples on the basis of crude protein or ᵢₙ ᵥᵢₜᵣₒ dry matter digestibility (IVDMD). In 1970 diseased fractions were significantly lower in percent crude protein and IVDMD and higher in percent acid detergent lignin, ADF, and CWC than nondiseased fractions.