THE INFLUENCE OF TEMPERATURE ON DEVELOPMENT AND REPRODUCTION OF THE EGG PARASITOID GONATOCERUS ASHMEADI

• Author(s): Leopold, Roger; Chen, Wenlong; Morgan, David;
• Abstract: The effect of temperature on the development and reproduction of Gonatocerus ashmeadi (G. ashmeadi )Girault was studied in environmentally-controlled chambers set at 12C, 16C, 20C, 24C, 28C and 32C. Our results showed that the parasitoid developed the fastest at 28C. The parasitoid took 27.1 days at 16C and 9.5 days at 28C to complete the development from egg to adult. The embryonic stage was 6.3 days at 12C, about 2 days at 16-20C, and 1 day at 24-32C. At 16-32C, the length of the first instar larval stage was about 1 day, but 6 days at 12C. The development of the second and third instars also varied with temperature. At 16C, the second and third instars were approximately 2 and 3 days in length, respectively, and 1 and 1.5 days at 28C. Continued exposure to 32C arrested the development of the third instar larvae. Prepupae developed faster as temperature increased, but slowed down when held at 32C. Pupae also developed faster as the temperature increased, but without slowing at 32C. Linear regression analysis showed that the threshold temperature for development was 5.5C, 3.4C, 8.3C, 5.2C, and 5.4C for embryos, first, second, third instar larvae, prepupae and pupae, respectively. The lower temperature threshold was 8.2C for egg to adult development. A total of 219.2 degree days above the minimum temperature threshold were needed to complete the development from egg to adult. Temperature also affected the emergence pattern of the G. ashmeadi adults. At 16C and 20C, adult emergence lasted 10 days and 5 days at 28C and 32C. The maximum emergence occurred on the first day of emergence at 20-32C while the emergence peaked on the second day at 16C. At 28C and 32C, about 92 and 88% parasitoids emerged within the first two days. At 20C and 24C, nearly 84 and 85% parasitoids emerged within the first three days. Temperature did not influence the sex ratio of the emerging G ashmeadi, but significantly affected the longevity of both sexes. At 16C, the life spans of female and male adults were 27 and 19 days, respectively, while at 28-32C, their life spans ranged from 6 to 8 days. The maximum lifetime fecundity of the female parasitoid occurred at 24C, with an average total of 105 eggs deposited. High temperature shortened parasitoid longevity and reduced lifetime fecundity. At 24C and 32C, G. ashmeadi deposited >10 eggs/day. At 16C and 20 C, parasitoid oviposition was 3 and 7 eggs/ day, respectively.
• Publication Date: Dec 2005
• Journal: 2005 Pierce's Disease Research Symposium