Effects of constant and fluctuating temperatures on development of the coconut hispine beetle,Brontispa longissima (Coleoptera: Chrysomelidae) and two species of parasitoid

Abstract

The larval parasitoid Asecodes hispinarum Bou?ek has been used to control the coconut hispine beetle, Brontispa longissima (Gestro) in Vietnam. Although A. hispinarum has succeeded in suppressing B. longissima in southern Vietnam, biocontrol has not succeeded in central Vietnam. One factor underlying this failure might be the high temperature during the hot season. In the present work, we examined whether A. hispinarum parasitises the beetles within the range of temperatures that occur during the hot season in central Vietnam and we evaluated the potential use of the pupal parasitoid Tetrastichus brontispae Ferrière. Development of the beetle and two parasitoids was investigated at two constant temperatures (28 and 30°C) and at fluctuating temperatures from 25 to 35°C (corresponding to temperatures during the hot season in central Vietnam). B. longissima reached adulthood in all the temperature treatments. More than 70% of A. hispinarum emerged from hosts at 28°C, but none emerged at 30°C or under fluctuating temperature conditions, indicating that A. hispinarum cannot be used as a biological control agent in central Vietnam. However, T. brontispae could reproduce the next generation at all temperatures. These results suggest that T. brontispae is a potential agent for continuous biological control of B. longissima in central Vietnam.