Model Description

The Oklahoma Pecan Nut Casebearer Model is a tool that has been developed to aid growers in proper timing of scouting for pecan nut casebearer (PNC). The Model calculates base 38F degree days from a start date that is unique to each location. The model was originally developed by entomologists at Texas A&M University in 1983, but has been field tested and verified under Oklahoma conditions during 1996-1997.

As just mentioned, the Oklahoma PNC Model is based on degree days, which are a measure of heat accumulated above a given temperature threshold from a specified start date. This particular model uses 38F as the temperature threshold for PNC development. The daily PNC degree days are calculated by:

[daily high temperature + daily low temperature]/2 - 38,

where negative values are not allowed. The degree days are calculated using weather information from the Oklahoma Mesonet, the state's automated weather station network.

For each Mesonet site, degree days are accumulated from a unique date that is based on the climatological (30-year) average of annual frost-free (32F) days at that site. According to the model, a degree-day total of 1831 indicates the date of first significant entry by PNC into the nuts. Additionally, based on our field observations, we recommend the following actions:

For insecticide treatment guidelines, the grower should consult the OSU extension publication on pecan nut casebearer.

In addition to the Site-Specific Interactive Model section, the Oklahoma Pecan Nut Casebearer Model web page features other sections. The Most Recent Output section displays the number of base 38F degree days which occurred over the last 24-hour period at every Mesonet site and the total accumulation of scab hours since each site's start date. For a time history of a specific Mesonet site, go to the Seasonal Output section to see daily model output at that site since its start date (daily base 38F degree days and total accumulations since the start date).