Foliar fungicide (pyraclostrobin) application effects on plant composition of a silage variety corn

The objective of this study was to determine the effect of foliar fungicide applied at various times during the growing season of corn on the chemical composition of corn leaves, corn ears, and corn stalks. Treatments were replicated once and assigned to 1 of 8 0.4-ha plots of corn, as follows: control (CON), corn receiving no foliar fungicide application; treatment 1 (V5), where corn received a mixture of pyraclotrobin and fluxapyroxad foliar fungicide (Priaxor, BASF Corp.) corn vegetative stage 5 (V5); treatment 2 (V5 + R1), where corn received two applications of foliar fungicide, a mixture of pyraclotrobin and fluxapyroxad at V5 and a mixture of pyraclostrobin + metconazole foliar fungicide (Headline AMP; BASF Corp.) at corn reproductive stage 1 (R1); and treatment 3 (R1), in which corn received one application of pyraclostrobin + metconazole foliar fungicide at R1. Evaluators at R1 and corn reproductive phase 3 (R3) reported signs of Gray Leaf Spot and Northern Leaf Blight on the foliage. Twenty-four individual corn plants from each treatment were collected at R1 and R3 for weight and length measurement. At each collection, corn was disassembled into leaves, stalks, flag leaf, and ears for chemical analysis. At R3, corn in V5 + R1 and R1 had less yellow leaves than CON and V5 (1.7, 1.5, 0.83 and 0.88 for CON, V5, V5 + R1 and R1, respectively; P = 0.03), and treated corn were taller than untreated (2.5, 2.9, 3.1, and 2.8 m for CON, V5, V5 + R1, and R1, respectively; P = 0.02). Fungicide treated corn stalks had greater lignin content (56, 64, and 50 g/kg DM for V5, V5 + R1, and R1, respectively) compared with untreated (46 g/kg DM; P = 0.03), with the greatest concentration from corn stalks in V5 + R1. Fungicide treated corn leaves had less ADF content (331, 283, and 330 g/kg DM for V5, V5 + R1, and R1; P = 0.01) and NDF content (584, 524, and 554 g/kg DM for V5, V5 + R1, and R1; P = 0.02) compared with untreated leaves (333 g/kg DM ADF; 569 g/kg DM NDF, respectively). In conclusion, results suggest that applications of foliar fungicide at V5 and R1 together may have a synergistic interaction on the fibrous content within the corn leaves, producing a higher quality feedstuff for ruminants when fungal disease is present.