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Arvin, CA, United States

Son Y.,University of California at Riverside | Groves R.L.,San Joaquin Valley Agricultural science Center | Groves R.L.,University of Wisconsin - Madison | Daane K.M.,University of California at Berkeley | And 3 more authors.
Environmental Entomology

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), vectors the bacterium Xylella fastidiosa that induces Pierce's disease of grape. This study determined the effect of temperature on the feeding activity of H. vitripennis adults and the resulting production of excreta. The Logan type I model described a nonlinear pattern that showed excreta production increased up to an optimal temperature (33.1°C), followed by an abrupt decline near an estimated upper threshold (36.4°C). A temperature threshold for feeding, at or below which adults cease feeding, was estimated to be 10°C using a linear regression model based on the percentage of adults producing excreta over a range of constant temperatures. A simulated winter-temperature experiment using fluctuating thermal cycles confirmed that a time period above the temperature threshold for feeding was a critical factor in determining adult survival. Using data from the simulated temperature study, a predictive model was constructed by quantifying the relationship between cumulative mortality and cooling degree-hours. In field validation experiments, the model accurately predicted the temporal pattern of overwintering mortality of H. vitripennis adults held under winter temperatures simulating conditions in Bakersfield and Riverside, California, in 2006-2007. Model prediction using winter temperature data from a Riverside weather station indicated that H. vitripennis adults would experience an average of 92% overwintering mortality before reproduction in the spring, but levels of mortality varied depending on winter temperatures. The potential for temperature-based indices to predict temporal and spatial dynamics of H. vitripennis overwintering is discussed. © 2010 Entomological Society of America. Source

Wang X.-G.,University of California at Berkeley | Levy K.,University of California at Berkeley | Son Y.,Pierces Disease Control Program | Johnson M.W.,University of California at Riverside | Daane K.M.,University of California at Berkeley
Biological Control

Long-term separation of a host from its native parasitoids may result in divergent thermal adaptation between host and parasitoid. The olive fruit fly, Bactrocera oleae (Rossi), most likely originated from Sub-Saharan Africa, but has since had a long invasion history in cultivated olives that spans geographical barriers and continents. This study compared three major thermal performance profiles (development, survival, and reproduction) across a wide range of temperatures (10-34°C) among a Californian population of the olive fruit fly and two African parasitoids, Psyttalia lounsburyi (Silvestri) and Psyttalia humilis (Silvestri), believed to have co-adapted with the fruit fly in its native range. Temperature ranges for the development and survival were 10-30°C for the fly, 10-28°C for P. lounsburyi, and 14-32°C for P. humilis. There was no difference in any thermal performance measured between two P. humilis populations (Kenya and Namibia) tested. The most suitable temperature ranges for reproduction were 22-30°C for the fly, 18-32°C for P. humilis, and 18-26 °C for P. lounsburyi. The results showed slight differences in the thermal profiles among olive fruit fly and both parasitoids species, with P. humilis being more heat tolerant whereas P. lounsburyi was less heat tolerant than the fruit fly. The results are discussed with respect to thermal co-adaptation and classical biological control of the olive fruit fly. © 2011 Elsevier Inc. Source

Daane K.M.,University of California at Berkeley | Wang X.,University of California at Berkeley | Duerr S.S.,University of California at Berkeley | Kuhn E.J.,University of California at Berkeley | And 2 more authors.
Environmental Entomology

Habrobracon gelechiae Ashmead (Hymenoptera: Braconidae) was studied as a parasitoid of the obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae) in California pistachio (Pistacia vera L.) orchards. Ovipositional behavior, adult longevity and fecundity, and the effects of temperature on developmental time and survival were determined. Habrobracon gelechiae develops as a gregarious, ectoparasitic idiobiont on late-instar C. rosaceana larvae. At 25°C, adult female wasps survived longer when provided honey and water (35.4 ± 4.9 d) or honey, water, and host larvae (34.4 ± 2.4 d) than when provided water (8.9 ± 1.1 d) or no food (5.9 ± 0.8 d). Over the adult lifespan, females parasitized 20.6 ± 2.1 hosts and deposited 228.8 ± 24.6 eggs. The intrinsic rate of increase was 0.24, the mean generation time was 18.15 d, and the double time 2.88 d. At constant temperatures, H. gelechiae successfully developed (egg to adult) from 15 to 35°C. The developmental rate was fit to a nonlinear model, providing estimates of the parasitoid's lower (10.5°C), upper (36.0°C), and optimal (33.3°C) development temperatures. Based on a linear model, 155 degree days were estimated for egg to adult eclosion. Temperature-dependent nonlinear model of survival showed similar shape with the model of development rate. The wasp developed under two diurnal temperature regimes, with 31.0 ± 13.3% survival at low (4-15°C) and 63.0 ± 11.4% survival at high (15-35°C) temperature regimes. The results are discussed with respect to H. gelechiae potential as a parasitoid of C. rosaceana in California's San Joaquin Valley. © 2013 Entomological Society of America. Source

Bruening G.,University of California at Davis | Kirkpatrick B.C.,University of California at Davis | Esser T.,Pierces Disease Control Program | Webster R.K.,University of California at Davis
California Agriculture

An outbreak of Pierce's disease of grapevine in the Temecula Valley in the late 1990s was one in a decades-long series of sporadic appearances of this infection in California. However, the new outbreak was qualitatively different because of the rapidity with which it spread in the vineyard and its appearance almost simultaneously at distant locations. The causative agent of Pierce's disease is the bacterium Xylella fastidiosa, and the distinct characteristics of the Temecula Valley outbreak were traced to the establishment of a new insect vector in California, the glassy-winged sharpshooter. Intensive and collaborative efforts among government agencies, industry and research institutions over 15 years have successfully contained the disease, and given scientists time to discover promising long-term potential solutions through genetic resistance. © 2014, University of California, Oakland. All rights reserved. Source

Son Y.,Pierces Disease Control Program | Nadel H.,University of California at Riverside | Baek S.,University of California at Riverside | Johnson M.W.,University of California at Riverside | Morgan D.J.W.,Pierces Disease Control Program
Biological Control

The effects of temperature on the development (egg-adult emergence) of Gonatocerus morgani Triapitsyn, a newly-described parasitoid of Homalodisca vitripennis (Germar), were determined at 14.8, 18.7, 23.5, 26.9, 28.7, 30.4, 32.8, and 33.8°C in the laboratory. Survival rate (percent adult emergence from parasitized host eggs) varied significantly among the experimental temperatures, with the highest (59%) and lowest (0%) occurring at 30.4 and 33.8°C, respectively. The survival rates (%) were fitted with a polynomial model to describe a temperature-dependent pattern. Developmental rates (1/d) across seven temperatures were fitted with the nonlinear Briere model, which estimated the lower threshold to be 8.06°C, the optimal temperature to be 29.22°C, and the upper threshold to be 33.49°C. A linear model fitted to developmental rates at 14.8-28.7°C indicated that 189.75. degree-days above the lower threshold of 9.71°C were required to complete development. A simulation model of G. morgani adult emergence was constructed to predict daily counts over the entire range of constant temperatures by incorporating the survival rate model, the Briere model, and the Weibull model. In outdoor validation, a degree-day model for predicting adult emergence showed ≤2. d differences between prediction and observation. Based on the observed temperature requirement, the insect could complete thirteen to sixteen generations per year in southern California, depending on weather and location. © 2011. Source

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