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Methods – temperature dependent development PowerPoint Presentation
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Methods – temperature dependent development

Methods – temperature dependent development

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Methods – temperature dependent development

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  1. Temperature dependent development, cold tolerance, predicted numbers of generations/year and predicted areas of establishment

  2. Methods – temperature dependent development • insects reared from egg to adult at 16, 20.5, 25.5, 29, 33, 34, and 36oC at 14:10, 60-70% RH • recorded days to molting • analyses: • linear regression to calculate degree day requirement and lower development threshold. • non-linear regression to estimate upper lethal threshold • use of historical weather data to map predicted numbers of generations/year across North America

  3. Results

  4. Effect of temperature on survival

  5. 13.4 Linear model DD = 1/slope = 355

  6. 0.07 All immature 0.06 0.05 0.04 Developmental Rate (Days 0.03 0.02 0.01 0.00 15 20 25 30 35 Temperature ( o C) 34.8 Non-linear model

  7. Predicted number of generations/year

  8. But......... • Map prediction assumes continual development throughout the year as long as temperatures are above the lower threshold • We know that this is not true due to reproductive diapause during the winter • Based on sampling data in Saint Lucie Co., we believe that diapause is initiated by mid November and ends in mid April. During this period, about 796 DD are accumulated. • Thus, the map overestimates the number of generations/year in St. Lucie Co. Florida by about 2.2 (796/355).

  9. Methods – cold tolerance • young adults held at 0, 5, and 10oC for 0.5, 1, 2, 4, and 8 days. • after chilling period, adults placed at room temperature and status (alive/dead) assessed after 24 hours

  10. Results – cold tolerance

  11. 100 0oC 80 60 Percentage survival (%) 40 20 0 0 1 2 3 4 5 6 7 8 9 10 Days

  12. Ltime90 ≥ 10 days at 0oC Ltime50 ≥ 4 days at 0oC Limitation of prediction: - we used summer insects - diapause insects may be more cold tolerant