FORAGE YIELD LOSSES IN HYBRID PEARL-MILLET DUE TO LEAF-BLIGHT CAUSED PRIMARILY BY PYRICULARIA-GRISEA

The effects of leaf blight, caused primarily by Pyricularia grisea, on forage yield and digestibility of pearl millet hybrids were evaluated in 1990, 1991, and 1992. A range of disease severities on Pyricularia -susceptible hybrid Tifleaf 1 and on the resistant, near-isogenic hybr id Tifleaf 2 were established by inoculation with P. grisea or by appl ication of chlorothalonil. Even with irrigation, no appreciable leaf b light developed in the dry 1990 season. In 1991 and 1992, disease seve rities (percentage of foliage with chlorosis and necrosis) in individu al plots ranged from 3 to 35%. Leaf blight severity in 1991 and 1992 w as negatively correlated (P < 0.01) with green plot yield, dry matter yield, and digestible dry matter yield. In vitro dry matter digestibil ity was unaffected by disease, and the response of dry matter concentr ation was inconsistent between years. Within the range of severities o btained, digestible dry matter yield decreased linearly with increases in leaf blight severity. Based on observed leaf blight severities of the Pyricularia-resistant Tifleaf 2, the regression equations estimate that minor pathogens that contribute to the leaf blight complex may r educe digestible dry matter yield of this hybrid by as much as 19%.