Citrus trees are at risk of sustaining damage by scale insect infestations. Scale insects damage citrus trees by extracting vital fluids from the tree, resulting in poor fruit quality and tree health.
According to the Texas Agricultural Extension Service, two varieties of scale insects primarily affect citrus trees. Armoured scale insects have a covering over their body that can be removed. Soft scale insects do not have this covering and they excrete a sticky substance known as honeydew.
Armoured scale insects include the purple scale, glover scale and the citrus snow scale, states the University of Florida. Soft scale insects that commonly attack citrus trees include the soft brown scale, cottonycushion scale and the Caribbean black scale.
The symptoms of scale insect infestation in citrus trees include leaf drop, discolouration of leaves, fruit that fails to colour and the death of twigs and branches. Heavy scale infestations can kill citrus trees.
The University of Florida states that chemical intervention is necessary when scales cause damage to plants and fruit. In many cases, natural predators keep scale insect infestations to a minimum in citrus trees.