Studies on a New Herbicide, Oxadiazon (G-315, 17623-RP)

III. The Selective Herbicidal Activity of Oxadiazon

Abstract

1) Oxadiazon, a herbicide which is active only under the light, showed in a germination test its herbicidal action against barnyardgrass (Echinochloa Crus-galli) was about ten times as strong as against rice plant. In the action to barnyardgrass, the large seeds were higher resistant to the oxadiazon than the smaller ones.
2) In the germination test of 14 kinds of gramineous plants; corn, wheat, rice and sorghum having large seeds showed an outstanding resistance to oxadiazon compared to the other 10 kinds of which seeds were by far the smaller.
3) In a test of transplantation to the soil incorpolated with oxadiazon using the rice and barnyardgrass which completely passed the albuminous stage, oxadiazon did not show any selectivity, giving a similar inhibition of leaf elongation and sheath browning to both plants.
4) In a test of exposure of the germinated rice and barnyardgrass, which were soaked in oxadiazon solution in the dark at the seed stage to the light; when a period of the light exposure was the same, activity of oxadiazon differed very much depending upon the plant growth stage at the time of exposure. Rice plants seemed to be susceptible in later stage than barnyardgrass.
From the above results, it was found that the timing of exposure to the light of oxadiazon-absorbed plants and the remained albumen level influence largely to the herbicidal activity of oxadiazon.