PROBLEM TO BE SOLVED: To provide an allelopathy effect or phytoalexin production enhancing agent, increasing allelopathy effect or phytoalexin production like weeding effect and antibacterial action by performing foliar application or rhizosphere fertilization for grains, vegetables, fruit vegetables and plants such as garden plants, and maintaining an environment where weeds hardly grow, and to provide a method for enhancing allelopathy effect or phytoalexin production, using the agent. SOLUTION: This plant allelopathy effect or phytoalexin production enhancing agent which includes an amino acid fermentation byproduct, a nucleic acid fermentation byproduct, amino acid or nucleic acid is applied to plants when cultivating the plants to suppress sprouting and growth of other plants at the periphery of the plants. COPYRIGHT: (C)2012,JPO&INPIT
