New pre-emergent herbicides formulated with bioactive compounds and compatibility with PGPB

Abstract

The increasing resistance of weeds to conventional herbicides has accelerated the search for sustainable alternatives. In this study, novel pre-emergent herbicides were developed as emulsifiable concentrates (ECs) containing the bioactive compounds citral and nonanoic acid, combined with various emulsifiers. Five ECs were prepared and characterized for physical stability and accelerated storage. ECs based on methyl esters exhibited superior emulsification properties. Selected formulations were tested for herbicidal activity against Lolium multiflorum, yielding IC95 values ranging from 0.017 to 54.70 µL/cm². Phytotoxicity on wheat seeds was assessed to estimate persistence after application. Compatibility with the plant growth-promoting bacterium (PGPB), Pseudomonas monteilii, was analyzed. While the ECs did not affect bacterial growth rates, they reduced final planktonic biomass, although biofilm formation by sessile cells remained unaffected in some formulations. Given the central role of biofilm–root interactions in plant health, these findings suggest that pre-emergent herbicides based on natural bioactive compounds may be compatible with PGPB. Further field studies are required to confirm their agronomic performance.