Pear yellow scale

Systematic position: The pear yellow scale (Diaspidiotus pyri) is classified within the order Hemiptera and the family Diaspididae. It is a highly specialized armored scale insect that causes significant damage to orchards by colonizing the woody parts of fruit-bearing trees.

Host plants: The primary host is the pear tree (Pyrus), but the pest is also commonly found on apples, quinces, plums, apricots, peaches, and various almond species. It prefers to colonize the trunks and scaffold branches of trees, though in severe cases, it can spread to fruits and leaves.

Biology and life cycle: The species completes one generation per year. It overwinters as first-instar nymphs (crawlers) protected by scales on the tree bark. As sap circulation begins in the spring, the nymphs continue their development into adults. The emergence of new crawlers typically occurs in early summer, at which point they disperse to find suitable feeding sites to establish new colonies.

Nature of damage and harmfulness: The scale insect feeds by piercing the plant tissue and sucking cell sap. This feeding process leads to the formation of reddish spots, bark cracking, and localized necrosis. Heavy infestations cause general tree decline, branch dieback, reduction in vigor, and a significant decrease in overall fruit production and tree longevity.

Control measures: Integrated pest management (IPM) is essential for effective control. Cultural practices such as pruning out infested branches, cleaning dead bark from trunks, and maintaining tree health are critical. Chemical control should be timed with the crawler emergence phase using systemic insecticides or horticultural oils during the dormant season to target overwintering stages.

• Regular orchard inspections to detect early signs of infestation.
• Sanitary pruning of severely affected limbs to reduce population pressure.
• Application of horticultural oils during the dormant period.
• Use of targeted insecticides during the crawler emergence peak.