Egg Cluster Characteristics of Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidea) in Sri Lanka under Laboratory Conditions

Abstract

Purpose: Spodoptera frugiperda is a recently introduced alien invasive pest in Sri Lanka which can be a threat to many crops including maize, paddy, sugarcane, green gram, vegetables and fruits. Identification of this pest at the egg stage is important in controlling the larval stages of development. Therefore, the present study was conducted to record the morphological and morphometric characters of the eggs of S. frugiperda for accurate identification at the initial stage. Research Method: Thirty-six egg masses of laboratory reared S. frugiperda were observed and measured under a dissecting microscope. Position of the egg clusters on plant, characters of the egg cluster and eggs, number of eggs per egg cluster and diameter of eggs were recorded. Findings: The study revealed that the female S. frugiperda laid eggs mainly on the underside of the leaf blade as clusters containing 9 – 200 (73 ± 7) eggs. Eggs were mostly arranged as single layers and when arranged in multiple layers, the bottom layer had a larger number of eggs than the upper layers. Most of the egg clusters were irregular in shape and some were covered with hairs. Eggs were spherical and initially creamy white in colour that gradually turned light grey when about to hatch. The diameter of eggs ranged from 0.38 mm to 0.55 mm. Originality/value: The study documents the morphological and morphometric characters of S. frugiperda eggs for accurate identification. Early detection of the insect pest facilitates the management of their population before causing an economic damage.