Latex coatings containing antifeedants: formulation, characterization, and application for protection of conifer seedlings against pine weevil feeding

Latex-based coatings for protection of tree seedlings against pest insect feeding are evaluated with respect to surface-, mechanical-, and release properties and antifeedant activity. The latex dispersion Eudragit copolymer (EC) was used to form the coatings, 2,6-di-tert-butyl-4-methylphenol (BHT) and cis-dihydropinidine (Alk) as antifeedants, and a thickener and a alkylglucoside based nonionic surfactant were used as additives to optimize the release- and mechanical properties of coatings. Coating characterization was performed with respect to surface morphology (atomic force microscopy, AFM) and surface wetting (contact angle), as well as to mechanical (tensile stress- and tensile strain at break) properties. Surface smoothness and wettability as well as elasticity increased with addition of the surfactant. The optimized coatings were found to be elastic and water resistant at 3-6 wt.% of BHT and 3 wt.% of surfactant. BHT was released into SDS/water at very low rates. Several formulations of BHT and Alk were efficient in preventing the feeding on conifer bark by a pine insect, Hylobius abietis both in laboratory (no-choice) and in field (3 months) tests.