Krista C. Shellie

Heating Rate and Induced Thermotolerance in Mexican Fruit Fly (Diptera: Tephritidae) Larvae, a Quarantine Pest of Citrus and Mangoes

Abstract A bioassay and graduated temperature water baths were used to document the induction of thermotolerance in third-instar Mexican fruit fly, Anastrepha ludens (Loew). The 99% lethal time dose for larvae exposed to 44°C core temperatures in artificial fruit is 61.5 min when a slow heating rate (120 min ramp) is applied, but only 41.9 min when a fast heating rate (15 min ramp) is applied. In electrophoretic profiles a heat inducible protein of molecular weight 32 kDa was detected in 76% of the larvae exposed to the slow ramp treatment, but only 42% of the larvae in the fast ramp treatment. Results from this research demonstrate that thermotolerance can be induced under conditions used to commercially disinfest fresh produce and highlight the necessity for specifying heating rates in quarantine treatment schedules.

Muskmelon (Cucumis melo L.) fruit ripening and postharvest quality after a preharvest spray of aminoethoxyvinylglycine

Abstract Aminoethoxyvinylglycine (AVG) at 60, 130, or 260 mg l −1 was applied to plots of ‘Primo’ and ‘Mission’ muskmelon 18 or 12 days prior to harvest. Melons were harvested twice from each plot and quality attributes evaluated at harvest or after cold storage. Melons harvested from plots sprayed with AVG had lower rates of ethylene production at harvest and after cold storage than melons harvested from control plots. Melon ethylene production after storage varied inversely with AVG application rate and was consistently lower when AVG was applied 7 days after full net. No difference was observed in flesh firmness, soluble solids, fresh mass or incidence of decay at harvest or after storage in melons harvested from plots sprayed with AVG. Uniformity of melon maturity within a plot was not enhanced by AVG, and plots treated with AVG required sequential harvests similar to control plots. Applications of 260 mg l −1 of AVG did, however, delay initial development of an abscission zone. Plots sprayed with 130 or 260 mg l −1 AVG developed a dose- related, leaf chlorosis readily visible 4 days after spraying. Plants with leaf chlorosis were rated equal in vigor to plants without leaf chlorosis.

Wine grape cultivar influence on the performance of models that predict the lower threshold canopy temperature of a water stress index

Abstract The calculation of a thermal based Crop Water Stress Index (CWSI) requires an estimate of canopy temperature under non-water stressed conditions (Tnws). The objective of this study was to assess the influence of different wine grape cultivars on the performance of models that predict Tnws. Stationary infrared sensors were used to measure the canopy temperature of the wine grape cultivars Malbec, Syrah, Chardonnay and Cabernet franc under well-watered conditions over multiple years and modeled as a function of climatic parameters – solar radiation, air temperature, relative humidity and wind speed using multiple linear regression and neural network modeling. Despite differences among cultivars in Tnws, both models provided good prediction results when all cultivars were collectively modeled. For all cultivars, prediction error variance was lower in neural network models developed from cultivar-specific datasets than regression models developed from multi-cultivar datasets. Overall, the cultivar-specific models had less prediction error variance than multi-cultivar models. Multi-cultivar models generally resulted in prediction bias whereas cultivar-specific models eliminated the prediction bias. All predictive models had an uncertainty of ±0.1 in calculation of the CWSI despite significantly different prediction error variance between models.