Prey-mimetic alginate microspheres for targeted control of red imported fire ants

The invasive red imported fire ant (Solenopsis invicta) poses a serious threat to ecology, agriculture, and public health. Existing baits are limited in their effectiveness due to behavioral resistance. To address this issue, we developed a biomimetic calcium alginate@indoxacarb microsphere bait (CA@IDC MBt) based on sodium alginate (SA) polysaccharides. SA polysaccharides form a matrix with specific mechanical properties and surface characteristics due to their unique β-D-mannuronic acid and α-L-guluronic acid block copolymer structure. The carboxyl cross-linked network not only provides structural stability (diameter 3.5 mm) but also enables precise loading of indoxacarb (loading rate 0.045 %, encapsulation efficiency 88.6 %). The CA@IDC MBt system effectively deceives ants by precisely mimicking both the chemical (epidermal alkanes) and physical (surface morphology) characteristics of natural insect larvae prey. Compared to commercial IDC MBt, CA@IDC MBt significantly improves bait recognition rates and group attack intensity. The sustained-release properties of SA polysaccharides (>80 h) effectively bypass the ants' vigilance mechanisms, achieving 100 % field efficacy without new nest formation. Behavioral experiments indicate that CA@IDC MBt can deplete 35-48 % of venom alkaloids within 21 days and completely eliminate ant colonies. This study reveals SA polysaccharide's key biomimetic role, advancing eco-friendly pest control with carbohydrate polymers.