The Black Olive or Oxhorn Bucida tree, Bucida buceras, is a widespread species found in the south Florida urban forest. Approximately 20% of the total shade trees in public areas of Coral Gables are Black Olive trees.
These shade trees are commonly attacked by two arthropods, an eriophyid mite, Eriophys buceras, and a caterpillar, Garella nilotica. By-products of these pests such as caterpillar frass and mite-induced galls cause severe staining of sidewalks, streets and vehicles underneath the tree canopy.
The staining is so aesthetically problematic that dissatisfied homeowners wish to remove the trees. Residents can remove this staining by scrubbing the affected pavement or structure using a diluted mixture of household bleach and water as a temporary solution.
Studies were conducted by The Davey Institute over a 4-year period in Naples and Coral Gables, Florida to evaluate insecticide treatments against these pests. During 2015 and 2016 in Coral Gables, abamectin trunk injections resulted in excellent reduction in gall formation and staining.
Abamectin trunk injections are proving to reduce the staining to property, and preserve the positive environmental benefits of mature Black Olive trees in the urban forest.
This represents an environmentally rational approach with none of the drawbacks associated with foliar applications or soil drenching.
The City of Coral Gables performs treatment injections of 2000 Black Olive trees every March and April during the peak season for mite and caterpillar activity.
Black olive trees provide shade but also lots of aggravation from the stains left beneath their branches. Rather than chop down the trees, Coral Gables is killing the pests that actually cause the mess.