Litchi Pests

Identification

• The lychee webworm is among the likely pests of litchi trees. Other common pests include the corky bark, a barkmining insect, and the citrus root weevils. The citrus root weevils damage trees by infesting the roots.

Description

• The lychee webworm is a moth that only has the litchi tree as its primary host. The moth is a native of the Caribbean and starts to develop its presence in the tree in November. The larval stage of the barkminer is a boring pest that eats its way into the bark. The citrus root weevil larvae damage the roots of tree and increase the susceptibility of trees to fungal infections. Mature weevils are less damaging to tree health.

Damage

• Trees infested with the lychee webworm display wilting and dying terminal shoots during February. The fruit has very fine bored holes or tunnels and there are webs on the infested tree areas. Corky bark feeding creates 6- to 18-millimeter, round, brown lesions on bark. The lesions have a corklike appearance. Roots weevil larvae feeding on roots eventually girdles and kills roots. Tree health suffers as the nutrient and water conducting ability of the tree is affected. Root rot fungi such as rhizoctonia and phytophthora are likely to infect roots through damage done by root weevils. Root weevil adults feed on foliage, leading to the notched and ragged edges on leaves. This damage is, however, minimal as compared to the roots damaged by the larvae.

Control

• Use pesticides with the active ingredient imidacloprid, rotenone, spinosad or azadirachtin for the effective control of the lychee webworm and citrus root weevil in litchi trees. Control is not recommended for corky bark as the pests do not cause any significant economic damage to trees.