Phytotoxicity and Soil Activity of HOE 23408

Abstract

Greenhouse and field studies were conducted to compare the phytotoxicity of HOE 23408 {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy]-propanoate} to several crops and annual grass weeds, and to determine the herbicides's soil mobility and persistence. In general, the order of susceptibility of 13 seedling grassy weeds remained constant, whether the herbicide was applied preplant incorporated, pre-emergence, or postemergence. The herbicide was most phytotoxic when it was applied either preplant incorporated or early postemergence. Grain sorghum [Sorghum bicolor(L.) Moench ‘BR-54′] and oats (Avena sativaL. ‘Cimarron’) were moderately susceptible to HOE 23408, whereas barley (Hordeum vulgareL. ‘Will’) exhibited marginal tolerance. Wheat (Triticum aestivumL. ‘Triumph 64′) and cotton (Gossypium hirsutumL. ‘Westburn 70′) showed tolerance to HOE 23408 at rates up to 6 ppmw, and soybean [Glycine max(L.) Merr. ‘Bragg’] and peanut (Arachis hypogaeaL. ‘Spanhoma’) demonstrated tolerance to concentrations as high as 24 ppmw. The soil mobility of HOE 23408 was similar to that of trifluralin (a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine). No soil phytotoxicity was found 8 weeks after herbicide application in the field or under laboratory incubation conditions of 5 or 10% soil moisture at 21 C. Dissipation was much slower at a temperature of 4.4 C, regardless of the soil moisture level.

Downy Brome (Bromus tectorum) Control with Diclofop in Winter Wheat (Triticum aestivum)

“…3). The findings agree with those of Wu and Santelmann (18). They found that diclofop dissipated from moist soil rapidly in the field and in the greenhouse, and that lowtemperature and low-moisture conditions significantly reduced diclofop degradation in soil.…”

“…'Cheney' wheat was planted in 30-cm-wide rows on October 13, 1978, but it did not germi nate until after 5.7 cm of rain fell in late November and did not emerge until early March, 1979, because of low soil temperature. Preemergence treatments were applied De cember 18,1978. Most downy brome emerged in early April, 1979.…”

The Relative Response of Two Foxtail (Setaria) Species to Diclofop

“…If the proportion of diclofop penetrating the leaves and reaching the site of phytotoxic action is the same for both species, then it might reasonably be concluded that at this leaf stage yellow foxtail is inherently more sensitive than green foxtail, since only one-third as much chemical was retained on the leaves of the former species. As supporting evidence, Wu and Santelmann (18) reported that yellow foxtail was, in fact, more sensitive than green foxtail to soil-applied diclofop where the primary site of uptake was the roots.…”

Seedling Tolerance of Cool-season Turfgrasses to Metamifop

“…Growth stage of grasses influences efficacy of AOPP herbicides, and treatments are often more phytotoxic when applied before tillering (Anderson, 1976;Derr et al, 1985;Wu and Santelman, 1976). Derr et al (1985) reported goosegrass, large crabgrass (Digitaria sanguinalis L.), and giant foxtail (Setaria faberi Herrm.)…”