The larval parasitoid Asecodes hispinarum Bouček 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 308C) and at fluctuating temperatures from 25 to 358C (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 288C, but none emerged at 308C 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.

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The coconut hispine beetle, Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae) is a serious pest of coconut palm. In this study, we developed an artificial diet for B. longissima so that the beetle could be used as a host for rearing two of its parasitoids, Asecodes hispinarum Boucek (Hymenoptera: Eulophidae) and Tetrastichus brontispae Ferrière (Hymenoptera: Eulophidae). The new artificial diet represents an improvement of our previous diet, which we used as a control. When beetle larvae were reared on the new diet, which contains cysteine but not cellulose powder and has twice as much coconut leaf powder as in the control, the adult emergence was 71% (approximately 2 times that in the control). We also examined the suitability of beetles fed on the new diet as hosts for the larval parasitoid A. hispinarum and the pupal parasitoid T. brontispae. The percentage of wasps that emerged from hosts that were fed the new diet was higher than that from the control-fed hosts. The new diet allowed both A. hispinarum and T. brontispae to produce adult wasps of the next generation, whereas the control only allowed T. brontispae to produce the next generation. These results suggest that the new diet is suitable for B. longissima and will facilitate mass-rearing of A. hispinarum and T. brontispae.

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