Ace the Certified Arborist Test 2026 – Branch Out and Leaf Your Mark!

The presence of sticky residue on leaves is a strong indicator of scale insect activity. Scale insects feed on plant sap, which can lead to the excretion of a sugary substance known as honeydew. This honeydew can accumulate on the leaves and other parts of the plant, creating a sticky film. This residue not only indicates the presence of these pests but can also lead to secondary issues such as sooty mold, which can further harm the plant's health.

The other options, while they may suggest various plant stressors or pests, do not specifically point to scale insect activity. Wilting leaves can be a sign of water stress or root issues. Discoloration of bark may indicate other types of insect activity or diseases rather than scales. Brown leaf edges typically result from environmental stress factors, nutrient deficiencies, or diseases unrelated to scale insects. Thus, the sticky residue on leaves is the most direct and specific sign of scale insect infestation.