Rufous scale

Systematic position. The Rufous scale (Selenaspidus articulatus) is a member of the order Hemiptera and the family Diaspididae. It is recognized as a significant agricultural pest worldwide, particularly in subtropical regions, where it poses a continuous threat to various plant species by sucking plant sap and weakening host vigor.

Host plants. The primary hosts for this pest include a wide variety of citrus trees such as oranges, lemons, and limes. Additionally, it has been recorded on other evergreen plants, including coffee, ornamental palms, and various tropical shrubs, which facilitates its spread in diverse botanical environments and nursery settings.

Biology and life cycle. The life cycle consists of the egg stage, the crawler (nymphal) stage, and the adult stage. The crawlers are the only mobile stage and are responsible for the dispersal of the population to new leaves and trees. Once settled, they secrete a waxy scale that covers their body, providing protection from environmental stressors and many contact pesticides.

Damage and economic importance. The Rufous scale causes injury by feeding on the sap of leaves, young twigs, and fruit. Symptoms include chlorotic spots, deformation, and defoliation. On fruit, the presence of the scale often creates unsightly spots, leading to rejection during the grading process and significant economic losses for commercial citrus growers.

Control measures. Effective management requires an integrated approach. This includes strict quarantine measures to prevent the spread of infested nursery stock, mechanical pruning of heavily infested branches, and the use of horticultural oils to smother the scales. Chemical control is most effective when timed precisely to target the mobile crawler stage, while biological control using parasitic wasps also plays a vital role in maintaining population levels.