The injury is not serious and is often mistaken for a disease.
Japanese beetle feeds on weigela.
Pesticides may not be effective if beetle populations are high. The grubs in the lawn can be controlled with pesticides or milky spore disease. Inspect the stems of unhealthy-looking plants to see if scales are present. Overwintering stages can be controlled with sprays of dormant oil. The preferred method of control involves regular inspection for early detection then spraying with dormant oil.