Certified Professional Horticulturist (CPH) Practice Exam

Which of the following is a likely consequence of allowing the honeydew-like sticky substance produced by sucking insects to remain?

1. Shiny yellowish patches enhanced by sun damage

2. Yellowing and dropping of the leaves at various levels of the plant

3. Black coating on leaves caused by sooty mold

4. Webbing in the axis of larger leaves and small branches

The correct answer is: Black coating on leaves caused by sooty mold

The production of honeydew by sucking insects, such as aphids and whiteflies, leads to specific ecological consequences due to the substance's characteristics. One significant consequence is the development of sooty mold, which thrives on the honeydew that accumulates on plant surfaces. This black coating forms when fungal spores settle into the sticky residue. Sooty mold can be detrimental to plants as it covers leaves and reduces photosynthesis by blocking sunlight. In contrast, while shiny yellowish patches may occur due to sun damage, this is not directly linked to the presence of honeydew. The yellowing and dropping of leaves can also happen for various reasons unrelated to honeydew, such as nutrient deficiencies or water stress. Lastly, webbing in the axis of larger leaves and small branches is commonly associated with spider mites rather than directly connected to the effects of honeydew from sucking insects. Thus, the presence of sooty mold effectively illustrates the issues that arise from honeydew accumulation.