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Poster Session

Poster Session

Poster Session

P05 - Progress towards La Crosse vector control strategies: evaluation of Natular DT and Altosid SR-20 in a La Crosse encephalitis endemic area

Wednesday, March 25, 2026
12:15 PM - 1:45 PM PDT
Location: Hall A
Abstract: La Crosse virus (LACV), a leading cause of pediatric arboviral encephalitis in the United States, remains endemic in western North Carolina, where Aedes triseriatus serves as the primary vector. Effective and sustainable control strategies targeting tree-hole habitats, the preferred larval sites of Ae. triseriatus, are essential to reduce human disease risk. We evaluated two larvicidal products, Natular® DT (spinosad-based) and Altosid® SR-20 ((S)-methoprene-based), under field conditions representative of LACV-endemic habitats.

Field trials with Natular DT conducted in 2025 in naturally occurring hardwood tree holes demonstrated strong and lasting suppression. A single early-season application (April 2025) achieved 100% efficacy 1-week post-treatment and maintained full control for more than 12 weeks. Cox proportional hazards modeling showed treated tree holes had only 9.5% of the larval hazard compared to controls (HR = 0.0946; 95% CI: 0.04–0.22; p < 0.001). Pupae were absent in treated holes within two weeks, indicating prolonged interruption of adult emergence.

Complementary 2024–2025 trials using Altosid SR-20 applied with a backpack blower demonstrated effective droplet penetration and larval control along forest edges. Although droplet density and size decreased with distance, inhibition of adult Ae. triseriatus emergence remained biologically significant up to 12 m, achieving 100% inhibition within 3 m and more than 75% at greater distances. Residual bioassays confirmed higher mortality at 5 m (72.7%) than 10 m (48.7%), indicating effective suppression in edge habitats.

Together, these studies highlight the potential of spinosad- and methoprene-based larvicides as complementary tools for LACV vector management. Early-season Natular DT applications provide durable protection in natural habitats, while Altosid SR-20 offers a flexible, operationally feasible approach for treating cryptic edge environments.