What is a common sign of an insect infestation beneath an interiorscape plant?

Choosing "dark and sticky areas" as a sign of an insect infestation beneath an interiorscape plant is correct because this phenomenon is often a result of the presence of certain pests, particularly sap-sucking insects such as aphids, whiteflies, and mealybugs. These insects feed on plant sap and excrete a sugary substance known as honeydew. When honeydew accumulates on surfaces beneath the plant, it can create dark, sticky areas by attracting sooty mold, which thrives on the honeydew and gives a dark appearance to the surfaces underneath the infested plants.

In contrast, the other options do not typically indicate an insect infestation. Brightly colored leaves might suggest healthy foliage or possibly certain types of fungal infections. Soft soil texture could indicate overwatering or root rot rather than a pest issue. Dry leaf edges are usually symptomatic of environmental stress from factors like low humidity, underwatering, or nutrient deficiencies, rather than a direct sign of an insect infestation. Thus, recognizing dark and sticky areas is an important indicator for diagnosing pest problems in interiorscape plants.