Field studies were conducted to determine the effect of several herbicides on soybean thrips numbers in soybean. Adult soybean thrips numbers in the preplant-incorporated and preemergent herbicide treatments were observed to be either greater than or equal to, but never less than, numbers in the control plots. Larval soybean thrips numbers were not observed to be affected by the preplant-incorporated or preemergent treatments. The postemergence herbicide treatment of naptalam plus dinoseb consistently reduced both adult and larval soybean thrips numbers. The other postemergent treatments did not affect numbers consistently.

Imazaquin and imazethapyr were applied postemergence to soybeans for control of 8- to 12-leaf rhizome johnsongrass and pitted morningglory in the field. At 8 weeks, johnsongrass control was 70% with 70 g ai/ha imazaquin plus 105 g ai/ha imazethapyr but was no more than 50% with a single application of either herbicide. Imazaquin at 70 g/ha plus imazethapyr at 35 g/ha interacted synergistically to provide 90% pitted morningglory control, while 140 g/ha imazaquin controlled 77%. Imazaquin at 70 g/ha with imazethapyr from 18 to 105 g/ha controlled both weed species equal to or better than that obtained with 140 g/ha imazaquin.

Field studies were conducted for 3 yr to evaluate the persistence of metolachlor and alachlor applied to ‘Centennial’ soybean and to determine their residual effect on ‘Mars' rice. At labeled use rates of metolachlor at 2.8 kg ai/ha and alachlor at 3.9 kg ai/ha, soil residue levels in the fall 5 months after application on Crowley and Midland silt loam soils averaged 0.04 and 0.05 ppmw, respectively. Metolachlor fall soil residues averaged 3.5 times higher when applied at 5.6 and 11.2 kg/ha compared to 2.8 kg/ha, but residues for labeled and double rates of alachlor were similar. In the spring 9 months after herbicide application, soil residues averaged over years did not exceed 0.06 ppmw. The 3-yr rice yields were not affected by residual metolachlor or alachlor.

Experimental adjuvants were tested to maximize herbicidal activity of sethoxydim on quackgrass and of bentazon on common lambsquarters. Efficacious adjuvants were identified by measuring the 14C-herbicide droplet spread and absorption, as influenced by various adjuvants, on the target weed. The absorption and droplet spreadability of sethoxydim and bentazon on quackgrass and common lambsquarters leaves were increased or were decreased depending on the type of adjuvant used. No correlation was found between sethoxydim droplet spread and absorption on quackgrass. With bentazon, the relationship between these two factors was greater. Thus, measurement of droplet spread, as affected by adjuvants, was useful only as a screening technique for bentazon. Blending surfactants with paraffinic oil or soybean oil to form a crop oil concentrate changed the efficacy of the surfactant compared to the surfactant by itself. Surfactants most effective as components of paraffinic-oil based crop oil concentrate were different from surfactants ideal for inclusion with soybean oil-based crop oil concentrate. Thus, the effectiveness of a crop oil concentrate depends on herbicide, surfactant, and oil types. In the field, several of the superior adjuvants identified in the laboratory enhanced sethoxydim and bentazon activity on grass and broadleaf weeds.

Field studies were conducted on a Crowley silt loam under weed-free conditions to determine herbicidal tolerance of ‘Centennial’ soybeans. Early season phytotoxicity and mature plant height reductions were caused by imazaquin at 140 g ai/ha applied preemergence (PRE) followed by imazaquin applied postemergence (POE) at both 140 (labeled rate) and 280 g/ha and for metribuzin plus chlorimuron at 360 plus 60 g ai/ha PRE followed by chlorimuron POE at 18 g/ha (double rate). Soybean yields, averaged across 3 yr, were reduced only for metribuzin plus chlorimuron PRE followed by chlorimuron POE at both 9 and 18 g/ha (10 and 15%, respectively).

The potential interactive effects between metolachlor [0, 0.1, 0.5, and 1.0 ppm (w/w)] and the air pollutant ozone (O3) [0.2 and 0.4 ppm (v/v)], on growth of corn, bean, and soybean were examined under controlled conditions. At both concentrations, O3 alone reduced corn and bean dry weights but only affected bean at 0.4 ppm (v/v). Shoot dry weight of corn was reduced by O3 plus metolachlor more than expected, thus indicating synergism. The expected dry weights of bean and soybean treated with metolachlor plus O3 were similar to or higher than expected, thus indicating additive or antagonistic interactions.

Research in Kansas from 1983 to 1986 evaluated early preplant (30 to 45 days) and late preplant (10 to 14 days) herbicide treatments for weed control before ridge-till planting in a soybean and sorghum rotation. Control of fall panicum and common lambsquarters at planting time averaged at least 95% for all early preplant and 92% for late preplant treatments. Where no preplant treatment was used, heavy weed growth in spring delayed soil dry-down, which resulted in poor ridge-till planting conditions and reduced plant stands, and ultimately reduced sorghum grain yields by 24% and soybean yields by 12%. Horsenettle population declined significantly, and honeyvine milkweed population increased. Smooth groundcherry populations fluctuated from year to year with no overall change.

Experimental objectives were to assess metribuzin tolerance of predominately privately developed soybean cultivars and to evaluate a greenhouse screening procedure. In field results in 1982, ‘Vinton 81’, ‘Northrup King 1884’ and ‘L77-1863’ soybean cultivars were extremely sensitive to metribuzin at 0.56 kg/ha, averaging 34% injury. The other 45 cultivars showed no significant injury at the 0.56 kg/ha rate, from 9 to 46% injury at 1.4 kg/ha, and 18 to 72% injury at 2.2 kg/ha. In greenhouse hydroponic studies, these same three soybean cultivars were killed, while the other 45 cultivars were injured from 15 to 82%. A good agreement of greenhouse and field data was determined, with a correlation coefficient of r = 0.82.

Oil-water emulsion stability was determined for crop origin and refinement of seed oils and their methyl esterified fatty acids (methylated seed oil) as influenced by emulsifiers and herbicides. Oil-in-water emulsion stability of one-refined, degummed, and crude seed oils was affected by the emulsifier. However, emulsion stability of methylated seed oil was not affected by the refinement of the seed oil used to produce the methylated seed oil or by the emulsifier. Oils without emulsifiers or emulsifiers alone added to formulated herbicide-water emulsions reduced emulsion stability depending upon the herbicide and emulsifier. Further, emulsion stability of formulated herbicides plus oil adjuvants was influenced by the oil type, the emulsifier in the oil adjuvant, and the herbicide. Oil-in-water emulsions improved or were not affected by increasing concentration of the emulsifier in the oil. However, T-Mulz-VO at a concentration greater than 10% with soybean oil or 5% with methylated soybean oil reduced emulsion stability with sethoxydim. Emulsion stability of herbicides with adjuvants depends upon the herbicide, the emulsifier, emulsifier concentration, and the crop origin, type, and refinement of oil.

Selective postemergence herbicides were applied broadcast to control wild-proso millet in soybeans early postemergence (early post), postemergence (post), and late postemergence (late post) when wild-proso millet was 2 to 8 cm tall, 3 to 15 cm tall, and 3 to 31 cm tall, respectively. CGA-82725, fluazifop, haloxyfop, and sethoxydim applied early post controlled 75% or less late-season wild-proso millet. Interrow cultivation following early post fluazifop applications improved wild-proso millet control and soybean yields. Higher rates of CGA-82725, haloxyfop, and sethoxydim applied post controlled 91 to 98% late-season millet, but resulting soybean yields were less than the hand-weeded check. Fenoxaprop, fluazifop, fluazifop-P, haloxyfop, quizalofop, and sethoxydim applied late post provided 93 to 99% late-season millet control and soybean yields equal to hand-weeded checks. Wild-proso millet emerging after early post or post herbicide applications contributed to reduced effectiveness from those treatments. However, most wild-proso millet emerged before late post applications and were controlled. Other herbicides including BAS-51702, clethodim, cloproxydim, and SC-1084 applied late post also controlled wild-proso millet in soybeans.

In 1986 and 1987, imazethapyr at 0.11 or 0.14 kg ai/ha and metolachlor plus imazaquin at 1.4 plus 0.16 kg/ha, applied preplant incorporated, controlled greater than 85% of red rice in soybeans. Red rice was controlled similarly by standard herbicide treatments of alachlor at 2.8 kg ai/ha, metolachlor at 2.2 kg ai/ha, and alachlor plus imazaquin at 2.5 plus 0.14 kg ai/ha. Eighty-four percent or more of red rice was controlled with single postemergence herbicide treatments of DPX-Y6202-31 at 0.14 kg ai/ha or imazethapyr at 0.11 kg ai/ha or by sequential postemergence treatment of DPX-Y6202-31 (0.07 plus 0.07 kg ai/ha) or clethodim (0.1 plus 0.1 kg ai/ha). Soybean injury was insignificant, and yields from treated plots were superior or equal to those from untreated plots.

Laboratory and greenhouse experiments were conducted to determine if activated charcoal can remove norflurazon from water and from a sand matrix, thereby reducing its availability for plant uptake. A ratio of approximately 10:1 activated charcoal:norflurazon completely inactivated norflurazon in water. In a sand matrix, activated charcoal: norflurazon ratios of approximately 100:1 and 200 to 300:1 completely reduced norflurazon injury to cotton and to soybean and corn, respectively. The amount of activated charcoal required to remove norflurazon from soil was estimated from bioassay and regression analyses. The accuracy of this method to eliminate injury to cotton without reducing control of prickly sida and seedling johnsongrass was confirmed by bioassay using a sandy loam soil.

A common sunflower isolate of Alternaria helianthi collected near Stoneville, MS, was pathogenic to cultivated sunflower and common cocklebur. Soybean, cotton, rice, grain sorghum, corn, wheat, and 22 other weed and crop species/varieties in nine botanical families showed no response or only minor symptoms. Therefore, further research is warranted to determine the potential of A. helianthi as a biocontrol agent against common cocklebur in geographic areas where sunflower is not a crop.