Diaspidiotus scales

The genus Diaspidiotus belongs to the Diaspididae family, commonly known as armored scale insects. These pests are highly specialized feeders that use their needle-like mouthparts to extract sap from the phloem of host plants. Their hallmark is the protective waxy shield they construct over their bodies, which acts as a barrier against predators and chemical pesticides.

These insects primarily target fruit trees, including apples, pears, peaches, and plums, as well as many ornamental shrubs and trees. Their presence is often detected by the discoloration of bark or fruit, and in severe infestations, they can cover the entire surface of branches and trunks, giving them a gray, crusty appearance.

The lifecycle of Diaspidiotus species typically involves overwintering as nymphs under the protective shield. In spring, when temperatures rise, the insects resume feeding and eventually mature. Females produce mobile first-instar nymphs, known as crawlers, which emerge from beneath the shield to find new feeding sites on the host plant or disperse to other plants.

Damage caused by these scales is significant and multifaceted. By removing plant fluids, they cause general debilitation, reduced vigor, and stunted growth. Furthermore, the toxic saliva injected during feeding causes distinct necrotic lesions or red spots on fruit, rendering them unsalable, and can lead to the death of small twigs and branches.

Control strategies require a well-timed approach, focusing on the crawler stage when the insects lack the heavy protective shield.

• Use of dormant oil sprays to smother overwintering nymphs.
• Application of selective insecticides during the crawler emergence period.
• Pruning and removing heavily infested wood to reduce local populations.
• Monitoring using pheromone traps to time treatments accurately.