Apple scale

Systematic position: The apple scale (Diaspidiotus marani) belongs to the order Hemiptera and the family Diaspididae. This pest is a specialist that primarily affects the bark of woody plants, specifically apple trees, and is characterized by the presence of a tough, protective wax shield that makes it difficult to manage during the stationary adult stage.

Affected crops: The primary host plant is the apple tree. The pest tends to cluster on trunks and scaffold branches. While it prefers apple trees, it can occasionally be found on other related fruit species within the Rosaceae family. Persistent infestations lead to significant loss of vigor in the host plant.

Biology and life cycle: The insect overwinters as a fertilized female hidden beneath a waxy shield on the bark. In spring, females lay eggs, which hatch into mobile larvae known as "crawlers." These crawlers disperse across the branches, locate suitable feeding sites, and eventually settle, losing their mobility and secreting a protective covering that characterizes their life stage.

Damage and harmfulness: Damage is caused by the insect piercing the bark with its stylet to feed on plant sap. Heavy infestations result in bark cracking, reduced vigor, and stunted growth of shoots. Over time, the tree's health declines significantly, leading to decreased yields and susceptibility to secondary pests and various pathogenic fungi.

Protection measures: Effective management requires a multifaceted approach focused on both mechanical and chemical control:

• Scraping away dead or loose bark during dormancy to remove overwintering sites.
• Applying dormant oil sprays to smother overwintering females.
• Targeting the "crawler" stage with systemic or contact insecticides when they are most vulnerable.
• Encouraging natural predators such as ladybugs and parasitoid wasps to reduce overall pest population density.