Integrating Growth Regulators, Fungicides, and Cultivars to Manage Late Leaf Spot in Peanut.

Crop protection strategies focused on minimizing quantitative crop losses offer a promising way to manage late leaf spot (LLS) and improve pod yield. To that end, we evaluated the physiological and yield response of peanut cultivars with different LLS resistance levels to an ethylene inhibitor (1-Methylcyclopropene; 1-MCP) and fungicide application. A study was conducted evaluating three peanut cultivars with variable resistance levels to LLS (Carver, York, Georgia 06G) under 1-MCP and fungicide sprayed and nonsprayed conditions in the field at Citra, FL. Data were collected on disease severity using the Florida 1-10 visual rating scale,  leaf area index (LAI) , leaf photosynthesis (A_sat) , and final pod yield. Progress of LLS severity on peanut canopy was slower in York and Georgia 06G compared to Carver under both fungicide sprayed and nonsprayed conditions. Application of 1-MCP did not slow the disease progression or reduction in leaf area loss in all the cultivars. Leaf area index had cultivar x fungicide interaction, whereby only Carver showed increase in LAI under fungicide sprayed compared to nonsprayed conditions. Photosynthesis data indicated a trend towards greater relative reduction in A_sat at a given disease severity in York and Georgia 06G compared to Carver. However, no differences in A_sat were observed with the application of 1-MCP. Final pod yield also indicated no 1-MCP effects; however cultivar x fungicide interaction showed increase in yield with fungicide application in Carver only. Results indicated that 1-MCP application did not result in yield benefits across all cultivars and the use of LLS resistant cultivars combined with fungicide application remains the best option to manage LLS and improve yields.