Certified Professional Horticulturist (CPH) Practice Exam

A customer brings in a leaf from their hibiscus plant with a sticky substance and louse-like insects. What pest might this indicate?

1. Lace bugs

2. Aphids

3. Scale

4. Mealybugs

The correct answer is: Aphids

The presence of a sticky substance on the leaf, known as honeydew, along with louse-like insects, strongly indicates an infestation of aphids. Aphids are small, soft-bodied insects that feed on plant sap, and they often excrete honeydew as they feed. This sticky residue can attract other pests and lead to a sooty mold on the leaves, further indicating their presence. While other pests, such as mealybugs and scale, can also produce honeydew and cause similar symptoms, aphids are generally more associated with soft, louse-like appearances and are known for their rapid reproduction and ability to form large colonies on plants. Lace bugs primarily feed on the underside of leaves but do not typically create the same sticky residue, and scale insects, while louse-like, are usually found in protective shells and may not produce significant honeydew compared to aphids. Understanding these characteristics helps in identifying and differentiating the specific pest affecting the hibiscus plant.