Model Description

The Oklahoma Pecan Scab Model is a tool that has been developed to aid growers in proper timing of fungicide application for pecan scab. Using data from the Oklahoma Mesonet, the state's automated weather station network, the Model calculates daily "scab hours" for all Mesonet sites. A scab hour is defined as one hour with relative humidity of 90% or higher and temperature of 70F or higher. Research at pecan field sites using Mesonet weather data has shown that the total scab hours in the 14 days preceding a scab rating was critical in correlating disease development.

The Model assumes that a correctly applied scab fungicide protects the crop for two weeks following application. When the customer clicks on a Mesonet site, the Model calculates the number of scab hours at that site that have occurred in the unprotected part of the last 14 days. If no fungicide application date was entered, the model uses March 15 as a default. Knowing the scab hours (given by the model) and the susceptibility of the pecan cultivar, the grower can decide whether to spray or not. The threshold for highly susceptible pecan cultivars is 10 scab hours, for moderately susceptible cultivars is 20 scab hours, and for natives and less susceptible cultivars is 30 scab hours.

The Oklahoma Pecan Scab Model is updated daily using weather data from the past 24-hour period ending at 5:00 a.m. CDT. Model results are available at this web site by 6:30 a.m. CDT each morning. Finally, the Model will operate from March 1 through August 31.

In addition to the Site-Specific Interactive Model section, the Oklahoma Pecan Scab Model web page features other sections. The Most Recent Output section to displays number of scab hours which occurred over the last 24-hour period at every Mesonet site and the total accumulation of scab hours since March 1. For a time history of a specific Mesonet site, go to the Seasonal Output section to see daily model output at that site since March 1 (daily scab hours and accumulated scab hours since March 1).