Scale Insects on a Red Mangrove leaf

Scale insects are notorious pests found on a variety of plants in both indoor and outdoor settings. Generally, scale insects encompass two groups: armored scales and soft scales. Both types feed on plant sap so when in high densities, they may cause yellowing of leaves and often premature leaf abscission. A major difference between the groups is that soft scales produce a honeydew like substance that serves as an excellent nutrient source for fungi growth. As a result, the presence of soft scales often elicits sooty mold to develop, which is relatively harmless to plants. Armored scales, however, do not produce any honeydew like secretions.

I suspect that the scale we found on red mangrove leaves is the Coconut Scale (Aspidiotus destructor), a species that is regularly reported on mangroves. This species of scale is in the armored scale group so it does not produce honeydew like secretions. In high densities the coconut scale can cause yellowing and leaf drop of infested plants and may lead to dieback.

Though we have not seen many areas with high densities of this scale, keep an eye out for them as you complete surveys as they could contribute to yellowing leaves and premature leaf dropping!