Black twig borer, Xylosandrus compactus has been identified as a serious insect pest in mahogany nurseries.
Nature of damage
The larvae feed on young tender leaves and other soft tissues of the terminal portion of the host seedling. They skeletonize the leaf or sometimes entire leaf is eaten.During sever infestations, tender part of most seedlings in the nursery was damaged by the larval feeding.
As a result repeated defoliation and damage to the apical shoot, the affected seedlings exhibit symptoms of die-back in tips and several axial buds start growing and this gives a bushy form to the crown of the seedling.
Infections could be easily noticed due to the presence of webbed frass with dried veins of the leaves made by larvae on the foliage. Larvae are nocturnal feeders.
Description of the pest
Larvae are about 3.5 to 4.5cm long when full grown. The color is dull brown in the older larvae with dark lateral strips on the both surfaces.
When about to pupate, the larvae rappel to the ground and pupate on the ground litter.Pupa is reddish brown in color and 2cm long. Pupation takes place within 5-8 days. The moth is brownish grey in color and 1.5-2cm in wingspan. The moth is nocturnal and hides in the vegetation during the day time.
Economic importance
A heavy defoliation reduces the vigor of the seedlings, thereby making it more susceptible to other pests especially for black twig borer damage. Then reduces the quality of seedlings.
Management
Hand collection of larval webs and destroying them will often provide satisfactory control in nurseries.
Any foliar spray used to control lepidopteron larvae can be applied to minimize the damage. Spraying the insecticide to the foliage at the beginning of first signs is most effective.
The Larva
The Pupa
Adult moth
The Leaves damaged by larvae
Typical Leaf web made by larva
Early stage of attack
Bushy appearance of crown due to larval feeding
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