The effects of MT-101 and its herbicidally active form, NOP, on the germination and seedling growth of hemp sesbania and rice were investigated. MT-101 decreased the germination of hemp sesbania by 57 and 90% at 0.05 and 0.5 mM, respectively, 1 d after treatment (DAT) in petri dishes. The germination, however, recovered such that there was no significant difference between treatments 4 to 6 DAT. NOP completely inhibited the germination of hemp sesbania at both 0.05 and 0.5 mM 1 DAT. However, germination also similarly recovered, and there was no difference between treatments 4 to 6 DAT. Neither MT-101 nor NOP decreased the germination of rice 3 to 6 DAT. In greenhouse trials preemergence (PRE) application of MT-101 at 2.25 kg ai ha⁻¹ decreased the density (number of plants pot⁻¹), plant height, and dry weight of hemp sesbania by 85, 67, and 91%, respectively. When applied postemergence (POST), MT-101 at 2.25 kg ha⁻¹ decreased the density, plant height, and dry weight by a maximum of 58, 61, and 82%, respectively, indicating that MT-101 may have greater activity when applied PRE. NOP had greater activity than MT-101 on hemp sesbania. NOP at 2.25 kg ai ha⁻¹ decreased the density, plant height, and dry weight of hemp sesbania 99, 78, and 97%, respectively, with PRE application. A POST application of NOP at 2.25 kg ha⁻¹ decreased the dry weight of hemp sesbania 91 to 94%. A PRE application of NOP at 2.25 kg ha⁻¹ decreased the dry weight of rice by 58%. Rice was not affected by POST applications of MT-101 but was affected slightly by NOP. These results suggest that MT-101 is a possible weed control agent in rice.

Nomenclature: MT-101, (naproanilide—common name approved by the Japanese Ministry for Agriculture, Forestry and Fisheries), 2-(2-naphthyloxy)propionanilide; NOP, 2-(2-naphthyloxy) propionic acid; hemp sesbania, Sesbania exaltata (Raf.) Rydb. ex A. W. Hill SEBEX; rice, Oryza sativa L. ‘Lemont’; cotton, Gossypium hirsutum L. ‘Deltapine 5415’.