Verbascoside from Verbena incompta is a plant root growth inhibitor.

The use of biopesticides has expanded rapidly in recent years; however, their use in weed control is less advanced. Herein, we describe the development of a weed control agent by screening 208 plant extracts (104 species) for their plant growth-inhibition activities, which resulted in 142 active samples (from 89 plant species). Verbascoside, isolated from the shoots of Verbena incompta, was identified as a growth inhibitor against rice root (EC50, 1.