Small larvae skeletonize the lower leaves. Large larvae feed over the whole plant. Severely damaged plants are very ragged in appearance. Larvae are yellow, oval, soft-bodied, grublike insects with darker, branched spines. Adults and larvae feed on the underside of leaves and eat the softer leaf tissues.
Damaged leaves appear netlike.
Mexican bean beetles attack soybeans throughout the season, but most damage occurs in August and September. Yellowish-buff to reddish beetles which usually have black margins and four distinct black spots on the back. Beetles eat small rounded holes in the leaves. Unexpanded leaves are favored, and damage is often more alarming than serious since holes expand with leaf growth. Beetles frequently skin pods in late season and scar the developing seed within.