Assessing activity of the pecan nut casebearer, Acrobasis nuxvorella, (Lepidoptera: Pyralidae) in Oklahoma using synthetic pheromone and simulation models

Scope and method of study. The purpose of this study was to evaluate a variety of tools that will enable Oklahoma pecan growers to make decisions about managing the pecan nut casebearer. Two existing biological models (Texas and Georgia) for predicting first entry of PNC larvae into fruit were field evaluated at seven sites using weather data supplied by the Oklahoma Mesonet. A new PNC pheromone was evaluated in two trap types and its efficacy compared to blacklights. The pheromone was also evaluated at three different heights in the pecan canopy to determine its affect on male PNC numbers. Final damage counts and two-day oviposition and larval damage counts were taken at the three heights to assess any height and/or pheromone effects. Data were analyzed using t-tests, SAS PROC MIXED, GLM, and REG.; Findings and conclusions. The Texas model was consistently late in predicting the entry date for 1996 although three of the sites were within one day of the observed entry. The Georgia model was consistently early in predictions for 1996. Both models showed mixes of over and under predictions for 1997. Because the Texas model appears more stable over time, degree-day thresholds from it were established for PNC activity in Oklahoma. A new PNC pheromone was evaluated in Pherocon® II and IIID traps, and compared to blacklight catch. Results obtained from trapping the spring emergent generation revealed the Pherocon® II mean catch was significantly greater than the Pherocon® IIID or blacklight catch. Although the Pherocon® II trap appeared to catch more moths in the second and third flight periods, no significant differences were observed between means of tamp types in the F1 and F2 generations. Capture of PNC was evaluated based on height of pheromone traps. A direct relationship was found between height of the trap and moth catch. No significant trends in damage by height were observed in 1996. Damaged clusters in 1997 were significantly different at each height with increasing damage from the bottom to top of the pecan tree.