Forbes scale

Systematic position: Forbes scale (Diaspidiotus forbesi) is a member of the order Hemiptera and the family Diaspididae. It is a well-known armored scale insect that acts as a significant pest in commercial orchards and home gardens.

Host plants: This pest is a polyphagous insect that primarily attacks pome and stone fruits. Common hosts include apple, pear, plum, cherry, peach, and apricot trees. It can also be found on various ornamental shrubs and small fruit bushes, often causing severe physiological stress to the plant.

Biology and lifecycle: The insect overwinters as first or second instar nymphs attached to the bark of branches and trunks. As sap flow begins in spring, the nymphs continue their development into adults. Depending on local climatic conditions, the pest can complete one or two generations per year, with the crawler stage being the main dispersal phase.

Nature of damage: Forbes scale feeds on plant sap, causing general decline, bark cracking, and premature leaf drop. Heavy infestations can lead to limb dieback. Furthermore, feeding on fruit results in the characteristic development of reddish-purple spots, which significantly reduces the marketability and quality of the harvest.

Management and control: Effective control requires an integrated approach. Cultural practices such as pruning out infested branches and maintaining tree health are essential. Chemical control is most effective when targeting the crawler stage using systemic insecticides or by applying dormant oil sprays in early spring to smother overwintering nymphs.

• Regular orchard pruning and canopy thinning.
• Removing and burning heavily infested branches.
• Using pheromone traps for timing crawler emergence.
• Biological control using parasitic wasps and ladybeetles.