Both corn earworms and tobacco budworms feed on soybeans. The two caterpillars look almost identical but are actually different species. Pyrethroids will control corn earwom but not tobacco budworms. Caterpillar-specific products (Blackhawk, Intrepid, Prevathod) are effective on both caterpillar populations. Determining what kind of insect populations you have is critical to choosing the right tool for the job.
This video, produced by the NC Small Fruit and Tobacco IPM team will help you determine which species you have.