RESUMEN
Field observations from pecan, Carya illinoinensis (Wangenh.) Koch, orchards in Texas were used to develop and validate a degree-day model of cumulative proportional adult flight and oviposition and date of first observed nut entry by larvae of the first summer generation of the pecan nut casebearer, Acrobasis nuxvorella Nuenzig (Lepidoptera: Pyralidae). The model was initiated on the date of first sustained capture of adults in pheromone traps. Mean daily maximum and minimum temperatures were used to determine the sum of degree-days from onset to 99% moth flight and oviposition and the date on which first summer generation larvae were first observed penetrating pecan nuts. Cumulative proportional oviposition (y) was described by a modified Gompertz equation, y = 106.05 x exp(-(exp(3.11 - 0.00669 x (x - 1), with x = cumulative degree-days at a base temperature of 3.33 degrees C. Cumulative proportional moth flight (y) was modeled as y = 102.62 x exp(- (exp(1.49 - 0.00571 x (x - 1). Model prediction error for dates of 10, 25, 50, 75, and 90% cumulative oviposition was 1.3 d and 83% of the predicted dates were within +/- 2 d of the observed event. Prediction error for date of first observed nut entry was 2.2 d and 77% of model predictions were within +/- 2 d of the observed event. The model provides ample lead time for producers to implement orchard scouting to assess pecan nut casebearer infestations and to apply an insecticide if needed to prevent economic loss.
Asunto(s)
Carya , Modelos Biológicos , Mariposas Nocturnas/fisiología , Animales , Vuelo Animal , Larva/fisiología , Nueces , OviposiciónRESUMEN
The cost-reliability of five sampling methods (visual search, drop cloth, beat bucket, shake bucket, and sweep net) was determined for four groups of predatory arthropods on cotton plants in Texas. The beat bucket sample method was the most cost-reliable sampling method for Orius adults, and the beat bucket and drop cloth were the most cost-reliable methods for Orius nymphs. The drop cloth and beat bucket were the most cost-reliable methods for sampling spiders. For sampling adult Coccinellidae, the sweep net and the beat bucket were the most cost-reliable. The visual sample method was the least cost-reliable method for Orius adults and nymphs and spiders. No one sampling method was identified as the optimum method for all four predator groups. However, the relative cost-reliability of the beat bucket method ranked first or second among the five sampling methods and this method was chosen for further evaluation in field studies in Texas and Arizona. The relative cost-reliability of 1-, 3-, 5-, and 10-plants per beat bucket sample varied with predator group, but multiple plant sample units were equal to or more cost-reliable than the one plant sample unit. Fixed sample plans for the beat bucket method were developed for Orius adults, Orius nymphs, spiders, and adult Coccinellidae, and the sum of these groups using the 3-, 5-, and 10-plant sample unit sizes. The greater cost-reliability of the beat bucket sampling method and its ease of use is of particular advantage in assessing predator densities in a commercial cotton field monitoring program.