Managing Sclerotinia Blight in Peanut: Evaluation of a Weather-based Forecasting Model to Time Fungicide Applications in Texas

Aim: To evaluate fungicide regimes were applications were made according a weather-based disease advisory compared to current application timings.

Study Design: Randomized complete block with four replications.

Place and Duration of Study: Studies were conducted during the 2008, 2009 and 2010 growing seasons on a producer farm located near Seminole Texas, Gaines County in fields with a history of Sclerotinia blight.

Methodology: Fungicide applications were made using a weather-based spray advisory model with varying Five-day risk index (FDI) thresholds that were calculated from daily average soil temperature, rainfall/irrigation and growth development. Five FDI treatments, a calendar-based and symptom-based (positive controls), as well as a non-treated (negative control) were evaluated. The cultivars Flavor Runner 458, Tamrun OL 02 and/or Tamrun OL07 were utilized in this study based on their differing reactions to Sclerotinia blight. Disease control, yield and quality for these timings were compared to the calendar-based and symptom-based programs, as well as the non-treated control.

Results: Appreciable levels of Sclerotinia blight were observed in 2008 and 2010. The application of fungicides led to a decrease in disease incidence compared to the non-treated control; however, few differences were observed among fungicide treatments. Overall, higher yields were achieved when fungicides were applied according to the calendar-based program. Similar yields were generally achieved for the lowest of the FDI thresholds evaluated and yields were generally lower when applications were delayed due to higher FDI thresholds. Grades were not affected by fungicide treatment; however, differences between cultivars were observed. Flavor Runner 458 consistently had higher grades than Tamrun OL07; however, Tamrun OL07 has improved resistance to S. minor.

Conclusion: Results from these studies suggest that the weather-based spray advisory model evaluated herein was not effective at improving upon the efficacy of fungicides for control of Sclerotinia blight in peanut. Moreover, applications for control of the disease in Texas should be made approximately 70 to 75 days after planting with a sequential application being made 28 to 30 days later.