Lounsbury scale

Systematic position. The Lounsbury scale (Rolaspis lounsburyi) is classified within the order Hemiptera and the family Diaspididae. As a member of the armored scale group, it is an economically significant pest, primarily impacting evergreen crops in subtropical climates.

Host plants. This pest shows a strong preference for citrus species, including lemons, oranges, and mandarins. In addition to commercial citrus crops, it can infest various ornamental plants, making it a persistent challenge in both commercial orchards and residential landscapes.

Biology and life cycle. The life cycle of Rolaspis lounsburyi begins with egg-laying, followed by the emergence of the first instar nymphs, commonly known as crawlers. The crawlers are the only mobile stage and are responsible for dispersal across the host plant. Once they settle and feed, they secrete a hard, protective waxy cover, becoming stationary for the remainder of their development.

Nature of damage and economic impact. The insect causes damage by feeding on plant sap from bark, leaves, and fruit. Symptoms of an infestation include chlorosis, wilting, stunted growth, and in severe cases, the death of individual branches or the whole plant. The presence of these scales on fruit skin significantly decreases marketability and poses a major threat to the profitability of citrus production.

Control measures. Managing Rolaspis lounsburyi requires a strategy that targets the vulnerable crawler stage while managing established populations.

• Application of contact insecticides specifically timed with the crawler emergence period.
• Use of narrow-range horticultural oils to suffocate the insects under their scales.
• Systemic insecticide treatments applied through soil or foliar sprays.
• Rigorous monitoring and removal of heavily infested plant materials.
• Biological control measures, including the introduction of natural predators or parasitoids where applicable.