LARVA SURVIVAL PENETRATING THE SCLEROTIC LAYER INSIDE THE COCOA POD
Authors: Meriam M.Y.
Journal Issue: Malaysian Cocoa Journal, Volume 14/2022
Keywords: Cocoa pod borer, larva, survival, sclerotic layer, cocoa pod husk, sclerotic layer
Published On: 10/05/2022
Abstract
Cocoa Pod Borer (CPB), Conopomorpha cramerella (Snellen) (Lepidoptera: Gracillariidae) is the most damaging pest of cocoa in Malaysia and other growing areas in the South East Asia region and in Papua New Guinea. Infestations by this pest, if left uncontrolled, may result in total yield loss or causing severe economic loss. Host plant resistance is one of the useful components in Integrated Pest Management (IPM) of this pest. In some of the cocoa clones may have smooth pod surface and hard sclerotic layer (SCL). There is a report mention that no evidence of resistance to CPB due to smooth pod surface. There is a report on larval mortality is higher with cocoa clone with hard SCL. This study was carried out to determine the percentage of larval survival from egg stage up to adult stage penetrating the SCL of the cocoa pod. This study was carried in the natural field condition by using the fresh cocoa pod which hanging up at the cocoa pod. The objective of this study is to evaluate the percentage of larval survival from egg stage up to adult stage penetrating the SCL of the cocoa pod. The study was conducted at Cocoa Research Station Quoin Hill in year 1993. Green matured cocoa pod under natural field condition were cage randomly with gravid female CPB for an eggs. Cocoa pod were checked daily for CPB egg and marked as a cycle using a soft needle. Cocoa pod contain CPB egg were protect from egg laying with other CPB, from rainfall using a plastic sheet and using a wire mesh cage to protect from infected from the mammalian pest. The CPB eggs were examined daily for egg hatchability. Every five (5) day interval, the cocoa pods were dissected stage by stage using disruptive method to examined the larva survival inside the cocoa pod. The places or sites and portions of the cocoa pod where the larvae penetrated were examined by peeling the epicarp of the cocoa pod husk. Every inches of the cocoa pod as draw in diagram in Plate 2 was examined for the existence of CPB larva. The number and the stage survival of larva inside the cocoa pod were recorded. The same process in year 1993 was repeated with new female of CPB in year 2017. The same procedure of study was carried out once again at Cocoa Research and Development Centre, Tawau, Sabah. Result from this study showed that when the larva spent 10 day time inside the cocoa pod, nearly 2 (two) % of the larva capable to emerged as an adult. Result from this study also showed that when the larva spent up to 30 days inside the cocoa pod, only 16 % of the larva capable to emerge to an adult stage. Result from this study also showed that in range of nearly 2 (two) % up to 16.0 % of the larva which hatched from the CPB egg were capable to penetrate inside the cocoa pod and tunnel out from the cocoa pod through in and out from SCL layer of the cocoa pod and became an adult.