Artificial diets for rearing the coconut hispine beetle,Brontispa longissima(Coleoptera: Chrysomelidae), and their suitability to two specialist parasitoids

Abstract

The coconut hispine beetle, Brontispa longissima (Gestro), is a serious invasive pest that infests young unopened fronds of coconut palms (Cocos nucifera L.) in Southeast Asia. We previously developed the first artificial diet for rearing B. longissima larvae, which contained a leaf powder of young coconut fronds. Because the fronds are required for healthy growth of coconut palms, it is necessary to reduce their use for rearing the beetles. In this study, we tested two new artificial diets for the beetle larvae, which contained the leaf powders of mature coconut leaves or orchard grass (Dactylis glomerata L.). Brontispa longissima successfully developed from hatching to adulthood on both the mature coconut leaf diet and orchard grass diet. The beetles reared on the mature coconut leaf diet and orchard grass diet developed faster than those reared on the young coconut leaf diet. Fecundity and egg hatchability of beetles did not differ among the three diet treatments. We then examined the suitability of beetle larvae or pupae reared on each diet as hosts for two specialist endoparasitoids, Asecodes hispinarum Boucek and Tetrastichus brontispae Ferriere. The survival rate from oviposition to adult emergence for A. hispinarum was 43.8% in hosts reared on a young coconut leaf diet, 77.1% on a mature coconut leaf diet, and 85.7% on an orchard grass diet. For T. brontispae, the survival rate was 70.0% in hosts reared on the young coconut leaf diet, 38.1% on the mature coconut leaf diet, and 66.7% on the orchard grass diet. Our results indicate these artificial diets can be useful for rearing B. longissima and its two parasitoids, helping to reduce the costs of mass rearing these insects.

A Comparison of Artificial Diets for Mass Rearing <I>Brontispa longissima</I> (Coleoptera: Chrysomelidae) as Hosts for the Larval and the Pupal Parasitoids

“…In the present experiment, the proportion of sixth-instar larvae with Diet C was lower than with the control diet. These indicate that Diet C is less optimal than fresh coconut leaves as food for B. longissima, but Diet C nonetheless enhanced the survival rate compared with the other diets in this study (Table 2) and with our previous diets ( Table 2; Ichiki et al 2009Ichiki et al , 2011.…”

“…The artiÞcial diets were prepared by modifying the diet reported by Ichiki et al (2009). Ichiki et al (2011) developed two artiÞcial diets made from mature coconut leaf powder and orchard grass powder as the main ingredients, but the survival rates of beetles that were fed these diets were lower than those that were fed the diet made from young coconut leaf powder reported by Ichiki et al (2009). Therefore, we used the diet developed by Ichiki et al (2009) as the control in the current study.…”

“…Thus far, we have developed three kinds of artiÞcial diets: these use the young coconut leaf powder, mature coconut leaf powder, and orchard grass (Dactylis glomerata L.) leaf powder as the main ingredients. However, the survival rates of the beetles reared on those diets were only 30 to 52% (Ichiki et al 2011). In addition, none of the diets allowed both A. hispinarum and T. brontispae to reproduce effectively, although each diet allowed one of the two species to emerge from Ͼ60% of the hosts.…”

“…Unfortunately, it is difÞcult to obtain sufÞcient quantities of fresh coconut leaves for use in massrearing programs. For this reason, we have tried to develop an artiÞcial diet for B. longissima to serve as an alternative food source (Ichiki et al 2009(Ichiki et al , 2011. Thus far, we have developed three kinds of artiÞcial diets: these use the young coconut leaf powder, mature coconut leaf powder, and orchard grass (Dactylis glomerata L.) leaf powder as the main ingredients.…”

Suitability of Monocots for Rearing Alien Coconut Pest Brontispa longissima (Coleoptera: Chrysomelidae)

“…More convenient plants will be needed for mass rearing of B. hngissima. Ichiki et al (2009) reported an artificial diet containing dried coconut leaf powder for B. hngissima, and 40% of larvae reared on the artificial diet grew to the adult stage. However, if continuously reared on this artificial diet, the adults did not lay fertile eggs.…”