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Frequency and Timing of Fungicide Applications for the Control of Gray Leaf Spot in Maize

January 1997 , Volume 81 , Number  1
Pages  41 - 48

J. M. J. Ward , Cedara Agricultural Development Institute, Private Bag X9059, Pietermaritzburg 3200, South Africa ; and M. D. Laing and F. H. J. Rijkenberg , Department of Microbiology and Plant Pathology, University of Natal, Private Bag X01, Scottsville, 3209 South Africa



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Accepted for publication 15 August 1996.
ABSTRACT

Timing and frequency of fungicide treatments for management and control of gray leaf spot of maize, caused by Cercospora zeae-maydis, were quantified with the logistic model and area under disease progress curve (AUDPC). Control was most effective when spraying commenced as disease severity levels reached 2 to 3% of the leaf area blighted and when lesions were restricted to the basal five leaves of the maize plant. Highest grain yields were achieved with treatments providing disease control until the crop was physiologically mature. To provide this length of control, the frequency and number of fungicide applications varied with the stage of host development when disease was first apparent; with early infections, more fungicide treatments were necessary to provide protection until physiological maturity. Yield responses to fungicides appeared to be a function of the growth stage of the host when sprays were initiated, the amount of disease at spray date, the length of fungicide control, and effective control through to physiological maturity.



© 1997 The American Phytopathological Society