Physiological time model for predicting adult emergence of western corn rootworm (Coleoptera: Chrysomelidae) in the Texas High Plains.
ABSTRACT Field observations at three locations in the Texas High Plains were used to develop and validate a degree-day phenology model to predict the onset and proportional emergence of adult Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) adults. Climatic data from the Texas High Plains Potential Evapotranspiration network were used with records of cumulative proportional adult emergence to determine the functional lower developmental temperature, optimum starting date, and the sum of degree-days for phenological events from onset to 99% adult emergence. The model base temperature, 10 degrees C (50 degrees F), corresponds closely to known physiological lower limits for development. The model uses a modified Gompertz equation, y = 96.5 x exp (-(exp(6.0 - 0.00404 x (x - 4.0), where x is cumulative heat (degree-days), to predict y, cumulative proportional emergence expressed as a percentage. The model starts degree-day accumulation on the date of corn, Zea mays L., emergence, and predictions correspond closely to corn phenological stages from tasseling to black layer development. Validation shows the model predicts cumulative proportional adult emergence within a satisfactory interval of 4.5 d. The model is flexible enough to accommodate early planting, late emergence, and the effects of drought and heat stress. The model provides corn producers ample lead time to anticipate and implement adult control practices.
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ABSTRACT: Mechanistic models for predicting species’ distribution patterns present particular advantages and challenges relative to models developed from statistical correlations between distribution and climate. They can be especially useful for predicting the range of invasive species whose distribution has not yet reached equilibrium. Here, we illustrate how a physiological model of development for the invasive Argentine ant can be connected to differences in micro-site suitability, population dynamics and climatic gradients; processes operating at quite different spatial scales. Our study is located in the subalpine shrubland of Haleakala National Park, Hawaii, where the spread of Argentine ants Linepithema humile has been documented for the past twenty-five years. We report four main results. First, at a microsite level, the accumulation of degree-days recorded in potential ant nest sites under bare ground or rocks was significantly greater than under a groundcover of grassy vegetation. Second, annual degree-days measured where population boundaries have not expanded (456–521 degree-days), were just above the developmental requirements identified from earlier laboratory studies (445 degree-days above 15.9°C). Third, rates of population expansion showed a strong linear relationship with annual degree-days. Finally, an empirical relationship between soil degree-days and climate variables mapped at a broader scale predicts the potential for future range expansion of Argentine ants at Haleakala, particularly to the west of the lower colony and the east of the upper colony. Variation in the availability of suitable microsites, driven by changes in vegetation cover and ultimately climate, provide a hierarchical understanding of the distribution of Argentine ants close to their cold-wet limit of climatic tolerances. We conclude that the integration of physiology, population dynamics and climate mapping holds much promise for making more robust predictions about the potential spread of invasive species.Ecography 01/2010; 33(1):83 - 94. · 5.12 Impact Factor
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ABSTRACT: The sum of effective temperature (SET) of adult Western Corn Rootworm (WCR) occurrence was determined based on several criteria. The risk of WCR occurrence was mapped, and the areas of continuous reproduction of WCR in the Czech Republic were identified. The daily soil SET, until the initial adult WCR occurrence was observed, ranged from 414 degree days (DD) when the lower threshold temperature (LTT) 12.5°C at 0.02 m depth to 719 DD (LTT of 10°C at a depth of 0.05 m). The daily air SET ranged from 415 DD (LTT 12.5°C at a height of 2 m) to 726 DD (LTT of 10°C at a height of 0.05 m).Plant Protection Science 01/2013; 49(2):89-97.
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ABSTRACT: BACKGROUND: Diabrotica speciosa (Germar) is an important pest in South America. Both the adults and the larvae are polyphagous, and its most susceptible host is maize. Factors behind the appearance of adults in the field and geographical variations in voltinism are unknown. This hinders the chances of implementing rational control strategies. RESULTS: This study compiles field collection data from four agricultural regions of Argentina to examine the number of generations and phenology of D. speciosa in the field. These data are correlated with climatic data in order to provide evidence of regional variations and probable environmental causes for the appearance of adult generations in the field. Results indicate that temperature has an important role in the appearance of new generations in the temperate distribution areas of D. speciosa, but not within its subtropical range, where teneral adults appeared all year round. CONCLUSION: Results suggest that the emergence of adults may be elicited by weekly average temperatures above 13 °C. In the temperate distribution areas of D. speciosa there could be at least three generations a year, and in the subtropical region at least five. No obvious or discrete voltinism pattern could be observed for D. speciosa in southern South America. © 2013 Society of Chemical Industry.Pest Management Science 01/2013; · 2.74 Impact Factor