Which non-target organisms are most at risk from Bti-based larviciding in aquatic habitats and how can risk be mitigated?

• A. Non-target birds; mitigate by timing sprays with bird migrations.
• B. Non-target fish; mitigate by reducing dosage.
• C. Non-target aquatic invertebrates; mitigate by habitat modification and label adherence.
• D. Non-target mammals; mitigate by applying at night.

Answer: (D)

Bti works by producing toxins that become active when ingested by mosquito larvae in the water, so exposure happens where larvae feed. Because of this, non-target aquatic invertebrates that share that same habitat are the groups most at risk in aquatic systems. To minimize this risk, use the product exactly as labeled and apply only to identified mosquito breeding sites, using the minimum effective dose to limit environmental exposure. Reducing or eliminating standing water through habitat modification lowers the number of larvae present and decreases the need for larviciding. Integrating non-chemical control methods and timing applications to minimize exposure to sensitive periods or habitats further reduces potential non-target effects. Following label directions and prioritizing targeted, site-specific applications keeps the focus on effective mosquito control while protecting non-target aquatic invertebrates.