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Temperature dependent development, cold tolerance, predicted numbers of generations/year and predicted areas of establishment. Methods – temperature dependent development. insects reared from egg to adult at 16, 20.5, 25.5, 29, 33, 34, and 36 o C at 14:10, 60-70% RH recorded days to molting

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


Methods temperature dependent development
Methods – temperature dependent development numbers of generations/year and predicted areas of establishment

  • 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


Results
Results numbers of generations/year and predicted areas of establishment


Effect of temperature on survival
Effect of temperature on survival numbers of generations/year and predicted areas of establishment


13.4 numbers of generations/year and predicted areas of establishment

Linear model

DD = 1/slope = 355


0.07 numbers of generations/year and predicted areas of establishment

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


Predicted number of generations year
Predicted number of generations/year numbers of generations/year and predicted areas of establishment


But......... numbers of generations/year and predicted areas of establishment

  • 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).


Methods cold tolerance
Methods – cold tolerance numbers of generations/year and predicted areas of establishment

  • 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


Results cold tolerance
Results – cold tolerance numbers of generations/year and predicted areas of establishment


100 numbers of generations/year and predicted areas of establishment

0oC

80

60

Percentage survival (%)

40

20

0

0

1

2

3

4

5

6

7

8

9

10

Days


Ltime numbers of generations/year and predicted areas of establishment90 ≥ 10 days at 0oC

Ltime50 ≥ 4 days at 0oC

Limitation of prediction:

- we used summer insects

- diapause insects may be

more cold tolerant


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