Abstract
The herbicidal activity of 4-ethyl-3-(3-chlorophenyl)-1-(3-isopropylphenyl) pyrrolidin-2-one (MT-146), was examined in a greenhouse for use as a paddy herbicide. MT-146 showed a remarkable herbicidal activity against Echinochloa crusgalli (L.) Beauv. var. formosensis Ohwi, Monochoria vaginalis (Burm. f.) Presl var. plantaginea (Roxb.) Solms-Laub., Alisma canaliculatum A. Br. et Bouche, Ammannia multiflora Roxb. and Rotala indica (Willd.) Koehne var. uliginosa (Miq.) Koehne at the dosage of less than 100g a. i./ha by pre-emergence application under flooded conditions; its efficacy against Scirpus juncoides Roxb. subsp. juncoides Roxb., however, was slightly lower. The compound showed no efficacy against Sagittaria pygmaea Miq. at the dosage of 10, 000g a. i./ha. The herbicidal efficacy of this compound against E. crus-galli was higher in deep water than in shallow, and was greatly affected by the leaf stage of the plant. The dosage showing 90% growth inhibition was 30-40g a. i./ha when the compound was applied at pre-emergence and 0.5 leaf stage, and it was 180g, 420g and 4, 300g a. i./ha at 1.0, 1.5 and 2.0 leaf stage, respectively.
MT-146 did not affect the growth of transplanted rice plants at the 2.5 leaf stage at the dosage of 200-400g a. i./ha when the transplanting depth of the rice seedlings was 0-2.5cm. Even if the roots of the seedlings were settled on the soil surface, no growth inhibition of the plants was observed. Nor did the herbicide inhibit the growth of rice plants at the dosage of 200-400g when water depth was 1-6cm.
MT-146 inhibited the chlorophyll formation of the seedlings of E. crus-galli at the concentration of 100ppb under light/dark conditions. The herbicide also inhibited the carotenoid formation at the concentration of 100ppb under both light/dark and continuous dark conditions. The carotenoid decrease may be related to the mode of action of MT-146.
