Why Is My Black Olive Tree Dripping Sap?

Identification

• Black olive tree is prone to the sooty mold caused by infestation from the black scale. The pests are 3/16 inch diameter, convex, hard-shelled black insects. There is a characteristic H-shaped ridge on the back.

Damage

• Black scales attach themselves to stems and foliage and feed on plant fluids. As they feed, they secrete sticky, honeydew-like liquid that starts to drip from the tree onto lower tree areas and ground. This is the sap dripping from the tree. The honeydew invites fungal infection that leads to the growth of sooty mold on the tree. Infestation from the pests and the resulting mold affects the tree's capability to transpire and photosynthesize.

Control

• Preventative measures include thinning the tree canopy to let light and air into tree. Plant the trees in well-ventilated areas. Apply narrow range oil to tree as soon as the insects hatch and are still in their crawling stage.