What symptoms would indicate the presence of soybean aphids in a field during flowering?

The presence of soybean aphids in a field can lead to distinct symptoms that are characteristic of their feeding habits and the secondary effects on plants. Stunted growth, sticky leaves, and the presence of black sooty mold are all indicative of an aphid infestation.

Aphids, including soybean aphids, feed on the sap of soybean plants. This feeding can result in stunted growth because the plant is deprived of vital nutrients and energy needed for healthy development. As they feed, aphids excrete a substance known as honeydew, which can cause sticky leaves. The honeydew provides an ideal environment for the growth of sooty mold, a fungal growth that appears as a black coating on the leaves. This mold can further impair photosynthesis by blocking light absorption.

In contrast, other options describe symptoms that can arise from various plant stress factors but don't specifically link to soybean aphids. General decline in plant health could stem from numerous issues, stunted growth with sticky leaves and black sooty mold is a direct indicator of aphid activity, making it the most relevant choice in recognizing their presence in a soybean field during flowering.