Ants marching up and down the trunk of an otherwise healthy-looking fruit tree? Branches or stems that look bumpy and shiny, as if coated with sugar water? These clues often point to a scale insect infestation.
- What are scale insects? These bugs are named for their shell-like, waxy protective covering. The small, inconspicuous pests that vary in color, shape, and texture by species.
- Why scale insects are a problem
- They feed by sucking plant juices
- Excess sap is excreted as honeydew, a sticky, sugary substance
- Ants feed on honeydew and actively protect scale insects
- Honeydew encourages sooty mold, a black fungus that coats leaves and reduces photosynthesis
- Types of scale insects
- Soft scale
- Rounded, convex covering that doesn’t detach
- May look waxy, cottony, or powdery
- Produces large amounts of honeydew
- Armored scale
- Tiny and flat with a hard, shield-like cover
- Cover can be separated from the insect
- Does not produce honeydew
- Correct identification is important because treatments differ
- Soft scale
- Plant damage to watch for
- Curled, yellowing, or wilting leaves
- Premature leaf drop
- Blemishes or discolored spots on fruit, leaves, or twigs
- Heavy infestations weaken plants and increase susceptibility to disease and other pests
- Management strategies
- Maintain healthy plants with proper irrigation and care
- Encourage natural enemies (parasitic wasps, beetles, lacewings, mites)
- Plant nectar- and pollen-producing flowers nearby
- Disrupt ants by:
- Pruning infested branches
- Removing weeds and plant bridges
- Applying sticky barriers like Tanglefoot
- Using ant baits when necessary
- Chemical control
- Most effective during the crawler stage
- Apply horticultural oil during dormancy or when crawlers are active
- Ensure thorough coverage of all above-ground plant parts
Click here to learn more about managing scale.