Comparisons of Temperature Measurements from Local Weather Stations and the Tomato Plant Canopy: Implications for Crop and Pest Forecasting
| Autor: | Michael P. Hoffmann, L. Theodore Wilson, Frank G. Zalom, Nita A. Davidson |
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| Rok vydání: | 1990 |
| Předmět: | |
| Zdroj: | Journal of the American Society for Horticultural Science. 115:861-869 |
| ISSN: | 2327-9788 0003-1062 |
| DOI: | 10.21273/jashs.115.5.861 |
| Popis: | Additional index words. Lycopersicon esculentum, Heliothis zea, Spodoptera exigua, agrometeorology, degree day models Abstract. Temperatures recorded by weather stations and within the canopy of tomato (Lycopersicon esculentum Mill.) crops were compared in fields near Davis, Calif., during Summer 1983 (60 days) and 1987 (50 days). For both years, the average maximum and minimum temperatures, daily temperature ranges, degree days per day, and total accumulated degree days were compared. In 1983, the mean maximum temperature at the weather station did not differ significantly from that in the canopy, but the mean minimum temperature at the weather station was signifi- cantly lower than that in the canopy. In 1987, the mean maximum temperature at the weather station was significantly higher than that in the canopy, but mean minimum temperatures did not differ significantly. Temperature ranges were significantly narrower for the weather station toward the end of the 1983 season, and significantly wider for the weather station at midseason 1987. Comparisons of degree days per day showed significant differences between means at the weather station and in the canopy in 1983, and among those at the weather station and the two degree day calculation methods used for temperatures recorded in the canopy. Total accumulated degree days based on temperature records at the weather station were lower than those in the canopy in 1983 but higher in 1987. In 1987, the single sine degree day calculation method overestimated degree days compared to the 2-hr triangulation method. The phenology of the tomato crop as predicted by weather station temperatures indicated that tomato maturation was underestimated in 1983 and overestimated in 1987. The rate of development for hypothetical populations of Heliothis zea (Boddie) and Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae) within the tomato crop was again underestimated in 1983 and overestimated in 1987, as based on temperature data of the weather station. The developmental rates of crops, their pests, and associ- ated natural enemies are regulated by the temperatures en- countered through the course of a growing season (Willmer, 1986). As a result, the concept of physiological time (degree days) is now widely used as a driving variable for predictive phonological models used in agricultural systems. The cal- culation of degree days can be accomplished using a variety of techniques, but most assume that the growth rate of the crop or arthropod is linearly related to ambient temperature within the limits of specified lower and upper developmental thresholds (Wilson and Barnett, 1983). One popular method, which uses daily maximum and minimum temperatures, is the single sine method of Baskerville and Emlin (1968). An- other method of calculating degree days is the triangulation or trapezoidal technique (Lindsey and Newman, 1956). Both methods can be adapted for use as 24-hr (single) methods that calculate degree days based on one maximum and one mini- mum temperature per day, or as 12-hr or smaller interval methods if maximum and minimum temperatures are recorded at more frequent intervals. Increasing the frequency at which temperature data are collected will improve the precision of both techniques (Wilson and Barnett, 1983). Fundamental to the accuracy of degree day calculations is the accuracy of the temperature data used. Temperature data may |
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