Saltcedars, Tamarix spp., exotic, invading deciduous shrubs or small trees from Asia and the Mediterranean area, have become the most damaging weeds of riparian areas in the western USA. We and our cooperators have obtained highly successful initial control of saltcedar by introducing the north Asian leaf beetle (Diorhabda sp., China/Kazakhstan ecotype) at five sites north of the 38th parallel, but they failed to establish farther south. In 2001, we discovered southern-adapted Diorhabda beetles on saltcedar and began testing them. In 2004, we released 2408 Greek beetles at Big Spring, TX; by September 2004, they had defoliated two trees, by 2005, 210 trees (0.8 ha) and by 2006, 7.3 ha of the saltcedar stand and 1.4 ha at Cache Creek, California, and had begun defoliating saltcedar at Pecos and Imperial, TX. The Uzbek beetles are increasing rapidly at Lake Meredith, TX and Fukang, China beetles at Artesia, NM, but the Greek and Tunisian beetles have not established near Kingsville in south Texas. We have revised the taxonomy of the five Tamarix-feeding Diorhabda ecotype/sibling species and predicted their climatic affinities in North America, correlated depletion of stored carbohydrates by beetle defoliation with plant death, developed pheromone attractants, remote sensing, improved release methods and a model of beetle dispersal and estimated possible damage to beneficial T. aphylla (Linnaeus) Karsten (athel) in the open field.
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.
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