Effect of Gamma Irradiation on Coconut Leaf Beetle, Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae)

Abstract

The effect of irradiation on the fecundity, egg hatchability, and longevity of the coconut leaf beetle (CLB) – Brontispa longissima (Gestro) – was studied using different doses of gamma radiation ranging from 20–50 Gy for pupa and adult males, and 20–40 Gy for adult females. The fecundity and fertility of adults decreased with irradiation dose. The pupae were more sensitive to irradiation than the adults based on LD50 values after 14 d. Adult females were more sensitive to irradiation than males based on fecundity and egg hatchability. No eggs were hatched at 40 Gy in irradiated females (IF) mated with unirradiated males (UM) and at 50 Gy in unirradiated females (UF) mated with irradiated males (IM), albeit with a significant effect on longevity at this dose. Using 45 Gy for mating competitiveness studies at a ratio of 1:15:1 (UF: IM: UM), wild females’ acceptance of IM was high based on the relative sterility index (RSI) value of 0.66.

Evaluation of Some Dicotyledonous Seed Extracts Against Coconut Leaf Beetle, Brontispa Longissima (Gestro) (Coleoptera: Chrysomelidae) and Sublethal Effect to an Endoparasitoid

“…Among the insect pests associated with coconut, Cocos nucifera L., the coconut leaf beetle (CLB), Brontispa longissima (Gestro) is one of the most serious in Southeast Asia and in the Philippines (Liebregts et al 2006;Chiki et al, 2009;Yebron and Batalon 2011;Obra et al, 2020). CLB is a leaf beetle that feeds on young leaves and destructive on both seedlings and mature coconut palms (Lu and Peng, 2017).…”

“…The egg are brown, flat and are laid singly or in groups of two to four on the still folded heart leaves (Lever, 1979 ). Eggs are incubated for about 3-7 days and the larvae undergo six larval instars on a period of 23-54 days (Obra et al, 2020). The pupal period is 4-6 days.…”

“…Diflubenzuron, carbaryl and carbofuran were found to have secondary exposure toxicity problem (Cruz et al, 2017). In addition, chemical resistanceof CLB is now widespread in coconutgrowing countries of Southeast Asia (Food and Agriculture Organization, 2007;Lin et al, 2012;Obra et al, 2020). Use of botanicals is still regarded as important component of Integrated Pest Management Programme (IPM) (Isman, 2006).…”

“…Botanicals can reduce cross-resistance Isman 1995, Leatemia andIsman 2004b), is target-specific (Du, et al, 2011), environmental-friendly (Vijayaraghavan et al, 2010) and act synergistically (Berenbaum, 1985). There is a vast array of plants which can serve as an endless source of ecologically-sound and safer pest control materials (Javier andBrown 2009, Lv et al, 2012;Mazid et al, 2011). Two potential plant species which may serve such purpose are at is Annona squamosa L.…”