Two adjuvants, Triton 11 XE (Isoctyl phenyl polyethoxy ethanol) and urea were tank mixed with four herbicides, methabenzthiazuron [N-(benzothiazol-2-yl)N,N′-dimethyl urea] at 1.0 and 1.5 kg ai/ha, terbutryn [N-(1,1-dimethylethyl)-N′-ethyl-6-(methylthio)-1,3,5-triazine-2,4-diamine] at 0.50 and 0.75 kg/ha, metoxuron [N-3-chloro-4-methoxyphenyl)N,N-dimethylurea] at 1.0 and 1.75 kg/ha, and isoproturon [(N-(4-isopropylphenyl)-N,N-dimethylurea] at 0.50 and 0.75 kg/ha and applied to weeds in wheat. Metoxuron reduced weed dry matter by 90% over a 2-yr period. Isoproturon, terbutryn, and methabenzthiazuron reduced weed dry matter by 82%. Tank-mixing of Triton 11 XE at 0.5% (v/v) with metoxuron at 1.0 kg ai/ha, terbutryn at 0.5 kg/ha, isoproturon at 0.5 kg/ha, and methabenzthiazuron at 1.0 kg/ha reduced weed density and biomass by 52 to 67% and enhanced grain yield by 33% over herbicide alone. None of the herbicides had any significant interaction with adjuvants in terms of weed control and grain yield.

A continuous-flow system was designed for the culture of aquatic weeds in the laboratory and used to examine the effects of low concentrations of terbutryn [N-(1,1-dimethylethyl)-N′-ethyl-6-(methylthio)-1,3,5-triazine-2,4-diamine] and diquat cation (6,7-dihydrodipyrido [1,2-:2′,1′-c] pyrazinediium ion) on algae (epiphyton) growing on surfaces of common elodea (Elodea canadensis L. C. Rich # ELDCA). Terbutryn did not affect the density of the epiphytic algal community, although development of the diatom component was favored at the highest concentration (50 μg/L). Diquat cation stimulated the growth of the epiphyton, particularly the diatoms, at concentrations as low as 5 μg/L. Possible reasons for this response included hormesis, differential tolerance to diquat, and facultative heterotrophy.

Under greenhouse conditions, postemergence herbicide effectiveness was greater when barnyardgrass [Echinochloa crus-galli (L.) Beauv.] plants were 5-or 10-cm tall as compared to 15-or 20-cm tall. Absorption of 14C-glyphosate [N-(phosphonomethyl)glycine] decreased from 58% of applied to 47% as plant height increased from 5 to 15 cm, and an additional reduction (to 32% of applied at 5 cm) occurred when terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine] was added to glyphosate. Translocation of 14C-glyphosate was reduced in older plants or when terbutryn was added to glyphosate. Water stress studies included soil moisture levels of 10, 20, 30, and 40% moisture (PW). Herbicide treatments were less effective at soil moisture levels below field capacity (30 PW). When soil moisture was 10 PW (-37 bar) absorption of 14C-glyphosate was greatly reduced in plants treated at both 7.5-and 15-cm heights with or without terbutryn. At 10 PW only 15 to 20% of applied 14C was absorbed whereas at 40 PW, absorption was over 45% and 62% with and without terbutryn, respectively. The addition of terbutryn to glyphosate resulted in decreased translocation for all soil moisture levels except the 20 PW treatment at the 15-cm height. Translocation of 14C was greatly reduced for plants in soils at 10 PW for both herbicide treatments.

Control of littleseed canarygrass (Phalaris minor Retz.), wild oat (Avena fatua L.), common lambsquarters (Chenopodium album L.), and field bindweed (Convolvulus arvensis L.) in dwarf wheat (Triticum aestivum L.) fields was studied with five herbicides and hand weeding. Terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine] and 1-benzthiazol-2-yl-1,3-dimethylurea controlled the weeds more effectively than did two hand weedings. Diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], nitrofen (2,4-dichlorophenyl p-nitrophenyl ether), and dichlormate (3,4-dichlorobenzyl methylcarbamate), proved only partially effective against weeds, and were therefore significantly inferior to two hand weedings. Spikes per meter of row length and test weight of wheat were increased significantly by 1-benzthiazol-2-yl-1,3-dimethylurea (1.5 to 2 kg/ha), terbutryn (0.5 kg/ha), and two hand weedings over the yields of the weedy check. The 1-benzthiazol-2-yl-1,3-dimethylurea showed a high degree of selectivity in the wheat crop at 2 kg/ha and increased yields to those of weed-free plots. Terbutryn was almost as effective as 1-benzthiazol-2-yl-1,3-dimethylurea, which increased the wheat yields over those of the weedy check by 19.8 and 42.4% during the 1974/75 and 1975/76 seasons, respectively. Tolerance of dwarf wheat to terbutryn at 0.75 kg/ha was variable, resulting in significant decreases in yield components and grain yield. Dry-matter yield of wheat was negatively correlated with the dry matter production of weeds.

Metribuzin at 0.42 kg ai/ha and metribuzin plus terbutryn at 0.28 plus 0.67 kg/ha were applied in the fall and spring to control downy brome in winter wheat from 1981 through 1985. Downy brome control averaged 88% from the fall-applied treatments and 63% from the spring-applied treatments. Yields from the fall- and spring-applied treatments averaged 136% and 132% of the check, respectively. Metribuzin plus terbutryn fall-applied controlled downy brome best (93%), and wheat yields were significantly higher than the checks in all experiments. Moreover, as downy brome density among locations increased, wheat yields decreased.

Foliar-applied herbicides were evaluated in one greenhouse and five field studies for control of silver beardgrass (Andropogon saccharoides Swartz. # ANOSA). In the greenhouse, terbutryn [N-(1,1-dimethylethyl)-N′-ethyl-6-(methylthio)-1,3,5-triazine-2,4-diamine] and the isopropylamine salt of glyphosate [N-(phosphonomethyl) glycine] at 3.4 kg ai/ha each consistently controlled silver beardgrass from 7 to 75 days after treatment. Field studies were conducted to investigate silver beardgrass control as influenced by herbicides and timing of herbicide application. Generally, glyphosate at 1.1 and 1.7 kg/ha satisfactorily controlled silver beardgrass with little or no permanent damage to the existing bermudagrass [Cynodon dactylon (L.) Pers. # CYNDA] turf. Decreasing water carrier volume from 374 to 187 L/ha did not affect phytoactivity of terbutryn at 3.4 kg/ha or glyphosate at 0.4, 0.6, 0.8, or 1.1 kg/ha.