Q: What is this white powdery stuff on the trunk of my citrus tree?
A: This pest is called citrus snow scale and believe it or not – it is an insect. Citrus snow scale attaches to the trunk and sometimes when populations are extremely high, it can be found on leaves and other parts of the citrus tree. The insect feeds on the plant juices diminishing the nutrients available to the tree. The insect reproduces in large numbers to cover the trunk tissue where it resembles “snow.” Armored scales are distinguishable from soft scales by the removable cover or ‘armor’. As crawlers, the females of snow scale insert their long mouthparts into suitable hosts and never move again. The immature males become immobile once they begin feeding and remain immobile until they emerge as winged adults. In severe infestations, the bark of the trunk or limb can split, making the tree vulnerable to fungal disease. Citrus snow scale has a tendency to pile up on top of one another making chemical application difficult to reach the bottom layer. Consider brushing the stems and branches with a soft toothbrush or larger soft brush first to remove some of the layers of the scale. Then apply insecticidal soap or all season horticulture oil. More than one application will be required.