When treating Bronze Birch Borer, which larval stage should be targeted?

• A. Young larvae
• B. Adults
• C. Pupae
• D. Eggs

Answer: (A)

Target the young larval stages because these early grubs are feeding in the outer bark and cambial region, where most insecticides and systemic treatments can reach them. Killing larvae at this stage stops the damage before the larva tunnels deeper into the sapwood, making control easier and more reliable. Eggs are laid on the bark and don’t feed, adults are mobile and less reachable with sprays, and pupae are sheltered under the bark, so they’re harder to affect with in-tree treatments. Once larvae grow larger, they bore deeper and become much harder to eliminate, which is why the best time to treat is when larvae are still young.