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The yellowmargined leaf beetle, Microtheca ochroloma (Stal) (Coleoptera: Chrysomelidae), is an adventive pest of cruciferous crops in the southeastern United States. Despite its pest status, there is limited information about the influence of temperature on development and survival of M. ochroloma. The objectives of this study were to assess the effect of temperature on the development and survival of immature stages, and determine the cold tolerance of immature and adult stages. Development was evaluated at 15,20,25, and 30°C, and cold tolerance was measured at 5,0, and -5°C inside environmentally controlled chambers. Survival of M. ochroloma from egg to adult was ≈80% at 15,20, and 25°C, but only 24% at 30°C. Mean developmental time was longest at 15°C (57 d) and shortest at 30°C (17 d). Leaf area consumed by the fourth instar was 7.4-fold lower at 30°C compared with consumption at 15, 20, or 25°C. The lower developmental threshold varied from 7.3 to 9.8°C and the total degree-days required to complete development from egg to adult was 333. At 5,0, and -- 5°C, the LT90 values for the first instar were shorter compared with all other stadia, suggesting that the first instar is the most susceptible to cold temperatures. Eggs were most cold tolerant, followed by pupae and adults. Based on the LT50 (13d) and LT90 (38d) of eggs at 0°C, the predicted northern distribution of M. ochroloma extends to Kansas, Illinois, Kentucky, and Virginia. [ABSTRACT FROM AUTHOR]

The tropical sod webworm, Herpetogramma phaeopteralis Guenée is a major turfgrass pest in the southeastern United States. We evaluated larval development on five artificial diets and at six temperatures (15, 20, 25, 30, 32.5, 35 ± 1°C) on St. Augustinegrass (Steiwtaphrum secundatum (Walter) Kuntze). Only larvae fed St. Augustinegrass and soy-wheat germ diets completed their lifecycles. None of the artificial diets tested (corn-based, soy-wheat germ, corn cob-wheat germ, corn cob-soy flour, or pinto bean) were suitable for rearing this species, because of high mortality and slower developmental time. Total developmental time (oviposition to adult) on S. secundatum significantly decreased from 47.8 d at 20°C to 21.1 d at 30°C, and then increased to 32.6 d at 32.5°C. Tropical sod webworm failed to complete larval development at 15 and 35°C. The relationship between temperature and developmental rate was described using linear (common and polynomial) and nonlinear models (Briere-1, Briere-2, and Lactin-2). The estimated lower temperature thresholds using a linear model for eggs, first, second, third, fourth, fifth, and sixth instars, prepupa, pupa, and total development were 10.1, 6.9, 12.3, 10.5, 15.3, 13.9, 9.1, 13.1, 12.0, and 13.1°C, and the thermal constant of these stages were 62.9: 66.2, 38.2, 40.3, 24.9, 32.3, 51.9,106.4,109.9, and 370.4 degree-days, respectively. The Briere-1 model provided the best fit with estimated lower, upper, and optimum thresholds for total development of 14.9, 34.3, and 29.4°C, respectively. The developmental requirements of H. phaeopteralis can be used to help predict the distribution and seasonal phenology of this pest. [ABSTRACT FROM AUTHOR]

The leaf beetle Gratiana boliviana Spaeth (Coleoptera: Chrysomelidae) was introduced from South America into the southeastern United States in 2003 as a classical biological control agent of tropical soda apple, Solanum viarum Dunal (Solanaceae). Temperature-dependent development and survival studies revealed that development was completed at temperatures >16°C and ≤34°C. The number of degree-days required to complete one generation was 341 and the estimated lower developmental threshold was 13.37°C. Using nonlinear regression, the upper lethal threshold was estimated to be 34-35°C. Cold tolerance studies revealed that the lethal time for 90% of adults (LT90) was 12.6 days at 5°C and 8.68 days at 0°C. Based on the developmental and cold tolerance data, a map predicting the areas of establishment and number of generations per year was generated, which suggests that the northern extent of the G. boliviana range in the USA will be near 32-33° north latitude. Fewer generations per year in more northern areas of the southeastern USA may decrease the effectiveness of this biological control agent. [ABSTRACT FROM AUTHOR]