Which insect feeds on both cotyledons and developing bean leaves in soybean fields?

The bean leaf beetle is known for its feeding habits on soybean plants, specifically targeting the cotyledons and young developing leaves. This beetle poses a significant risk to soybean crops, especially in the early growth stages. The damage caused by the bean leaf beetle can lead to reduced plant vigor, stunted growth, and decreased yields, which is critical for soybean production.

In contrast, while the green cloverworm does feed on soybean leaves, it primarily targets mature foliage rather than the cotyledons and young leaves specifically. The two-spotted spider mite is an arachnid that feeds on the plant’s leaves but does not specifically target cotyledons. The seedcorn maggot is focused on feeding on seeds and seedlings, primarily impacting crop establishment rather than feeding on the foliage.

Thus, the bean leaf beetle is the primary insect to consider when looking at damage from cotyledons and developing leaves specifically in soybean fields. This makes it the correct choice in this context.