What manifestation indicates a sap-feeding insect infestation on plants?

A sap-feeding insect infestation typically leads to wilting and leaf drop due to the insects extracting vital nutrients and moisture from the plant. When these insects, such as aphids or spider mites, feed on the sap, they disrupt the plant’s ability to transport water and nutrients effectively. This can cause the leaves to lose turgor pressure, leading to wilting. As the situation worsens, plant tissues may die off, resulting in leaf drop.

The other options do not directly relate to the effects of sap-feeding insects. Drooping flowers could be a sign of various stress factors, such as insufficient water or light, and are not specific to sap-feeding damage. Dark soil may indicate poor drainage or soil health issues rather than an insect infestation. Yellowing leaves can result from several factors, including nutrient deficiency or overwatering, but do not specifically indicate sap-feeding insect activity. Thus, wilting and leaf drop best capture the manifestation of a sap-feeding insect infestation.