Glasshouse Study on Herbicidal Activity of Pretilachlor on Rice and Echinochloa oryzicola VASING.
1990 Volume 35 Issue 2 Pages 155-163
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1990 Volume 35 Issue 2 Pages 155-163
Glasshouse experiments were conducted to investigate effects of plant age and other factors affecting the contact of pretilachlor [2-chloro-2′, 6′-diethyl-N-(2-propoxyethyl)-acetanilide] with plants on the herbicidal activity against rice (Oryza sativa L. cv. Nihonbare) and Echinochloa oryzicola VASING..
The pretilachlor activity on seeded rice was higher when rice was shallowly seeded than when seeded deeply, and its activity on rice seeded shallowly decreased more sharply than that on Echinochloa as leaf stage at application developed (Figs. 1 and 2). Seeding depth did not affect the activity on Echinochloa at all (Fig. 2), which depended only on leaf stage at the time of pretilachlor application (Figs. 1 and 2).
Shallow planting (Table 1) and water percolation (Table 2) intensified the phytotoxicity of pretilachlor on transplanted rice, which was not affected by water depth (Table 3). Neither water depth nor water percolation affected the pretilachlor activity on Echinochloa at all (Tables 4 and 5).
Pretilachlor applied only to the soil surface was selective between rice and Echinochloa seeded at 15mm depth; applied to the position of seed or root, however, the chemical was not selective (Figs. 3 and 4).
The role of soil treatment was dominant in the activity of the overall treatment (combination of soil and foliar treatments) on the grasses, and that of foliar treatment was negligible in rice and slight in Echinochloa when pretilachlor was applied at about the 2 leaf stage of the plants (Fig. 5).
The following conclusions were therefore drawn:
1) The primary bases for the selectivity of pretilachlor between transplanted rice and Echinochloa are difference in availability of the chemical to the site of uptake and difference in plant age:
2) physiological difference in the response to pretilachlor additionally contributes to the selectivity:
3) the pretilachlor activity on the grasses greatly depends on the degree of its contact with the coleoptilar node: and
4) the contact of pretilachlor with the foliar does not play any role in its phytotoxicity on the rice crop.
