Tolerance of tomato cultivars to diphenyl ether herbicides applied postemergence was determined in greenhouse and field experiments. In greenhouse experiments, tomato cultivar tolerance differed, but acifluorfen injured all genotypes. ‘Carmen’, ‘PetoPride 2’ and ‘Heinz 1350’ tolerated acifluorfen while ‘Advantage’, and ‘Red Plum’ were susceptible. Growth habit and tolerance to 1.1 kg ae/ha acifluorfen was significantly correlated (r2 = 0.24). Field-planted tomato cultivars' tolerance to diphenyl ether herbicides applied postemergence differed. Heinz 1350 and ‘Veeroma’ tolerated diphenyl ethers, while Advantage and Red Plum were susceptible. Potency of diphenyl ethers also varied with oxyfluorfen the most injurious and acifluorfen and fomesafen the least injurious.

Field and greenhouse studies were conducted to evaluate the following growth regulators: ABG-3034, a cytokinin, benzylaminopurine (BAP); alkanolamine salt of 2,4-D; gibberellic acid (GA); isopropylamine salt of glyphosate; kinetin; napthaleneacetic acid (NAA); and PP333, an experimental antigibberellin compound, and the herbicides: dimethylamine salt of dicamba and potassium salt of picloram alone and combined on the growth and control of leafy spurge. The results of greenhouse and field studies show that growth regulators did not enhance the performance of herbicides in controlling leafy spurge.

Mefluidide, Mon 4620, paclobutrazol plus mefluidide, and flurprimidol plus mefluidide temporarily injured and discolored tall fescue without reducing shoot density. Mefluidide at 0.43 kg ai/ha and Mon 4620 at 2.8 kg ai/ha suppressed vegetative growth of mowed grass 4 weeks while unmowed grass was suppressed for 8 weeks. Mefluidide at 0.14 kg/ha with either flurprimidol at 1.1 kg ai/ha or paclobutrazol at 1.1 kg ai/ha suppressed vegetative growth of mowed tall fescue for 5 and 6 weeks, respectively. Combination treatments also suppressed the growth of nonmowed tall fescue 8 to 10 weeks. Mowing effectively suppressed seedheads for 12 weeks when the grass was mowed at 3 and 6 weeks, while mowing only once at 4 weeks did not. Seedhead suppression was not improved with weekly mowing compared with two mowings. Mowing influenced the performance of plant growth regulators on vegetative growth and seedhead control but not plant injury, quality, or shoot density.

Experiments were conducted at Bridgeport, NE, during 1983 through 1987 to select alternatives for silvex and 2,4,5-T for sand sagebrush and brittle pricklypear control. Of the six herbicides examined, the butoxyethyl ester of 2,4-D at 2.2 kg ae/ha was equivalent to the propylene glycol butyl ether ester of silvex or 2,4,5-T for sand sagebrush control. The potassium salt of picloram at 0.3 kg ae/ha was equal to silvex for brittle pricklypear control.

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.

The importance of tall fescue as a pasture grass is diminished when infected with the fescue endophyte. The availability of fungus-free seed has necessitated the development of systems to kill the infected sod before interseeding fungus-free seed. Field studies were conducted to evaluate the response of fescue sod to foliar-applied herbicides as single and sequential applications during the fall and spring. Sequential applications of paraquat at 0.14, 0.28, and 0.56 kg ai/ha in September and October and glyphosate at 0.84 and 1.7 kg/ha applied as single or sequential applications in September and October resulted in more than 90% kill of the tall fescue sod. Spring treatments of paraquat and glyphosate were less effective than those applied in the fall. Dalapon, fluazifop-P, HOE-39866 [glufosinate (proposed name)], sethoxydim, and simazine did not effectively kill the sod.

Variation in size and distribution patterns of granules of a blank hexazinone formulation were studied in both ground and aerial applications. Granule size ranged from 2.5 to 93 mg with 90% of the granules between 5 and 35 mg. The granule size frequency among weight classes did not change within a 5-m wide test swath from a truck-mounted applicator, indicating no impact on the distribution of active ingredient. The ground applicator did not produce a uniform deposition of granules. Average granule depositions were 11 ± 5 kg/ha and 16 ± 8 kg/ha for the target rates of 20 and 40 kg/ha, respectively. Aerial application with a helicopter-mounted bucket spreader produced a 27-m wide effective swath. Average deposition rates were 19 ± 5 kg/ha and 39 ± 9 kg/ha for the target rates 20 and 40 kg/ha, respectively. The optimal sample sizes for aerial application were estimated to be 27 and 50 samples for 40 (±10%) and 20 (±10%) kg/ha rates, respectively, with 90% certainty.

Five broadleaf crops, alfalfa, peanut, soybean, tobacco, and tomato, were tested for their susceptibility to three broomrape species, branched, Egyptian and crenate, in the greenhouse. All five crop species were parasitized by one or more broomrape species. Peanut plants were most susceptible and soybean plants were least susceptible to parasitism by broomrape. Egyptian and branched broomrapes had a wider host range affecting plants in both the Solanaceae and Fabaceae. Crenate broomrape mainly infected plants belonging to Fabaceae, except for the few attachments to tomato and tobacco. Apparently, this is the first report on parasitism of peanut plants by branched broomrape and that of peanut and alfalfa plants by crenate broomrape. Parasitism of soybean plants by any of the broomrape species also was observed for the first time in these experiments. These results indicate that broomrapes, although not a major problem on any of the crops in the United States, could parasitize several major broadleaf crops should the parasite become established.

An area of a shrink-swell clay soil (Tunica clay, Vertic Haplaquept) with an established population of redvine, trumpetcreeper, honeyvine milkweed, redberry moonseed, and maypop passionflower was treated with dicamba once in the fall of 1983. The effect on perennial vines was determined for the following 4 yr in three rotational cropping systems involving winter wheat, soybean, corn, and sorghum, all with and without irrigation. Dicamba reduced the population of perennial vines 80% over 4 yr. Redvine and trumpetcreeper, the first and second most abundant species, were reduced by over 83 and 76%, respectively. Yield of soybean increased 17% in 1985 and 1987 while corn yield increased 9% in 1986 with dicamba use. In 1984 no effects on crop yield were measured. This inconsistent crop yield reponse after dicamba treatment, even though perennial vines were suppressed, must be considered in evaluating the economics of using dicamba for perennial vine control.

Rhizome johnsongrass control with sethoxydim and clethodim was evaluated with the addition of three adjuvants: Agrioil3, BAS8153, and Li7003. Johnsongrass control was similar with the three adjuvants when either sethoxydim or clethodim was applied alone, but when bentazon was added, johnsongrass control declined with both sethoxydim and clethodim. Control generally declined less with BAS815 than with Agrioil or Li700, but the addition of BAS815 did not completely reverse the effects of adding bentazon to sethoxydim or clethodim. Johnsongrass control was not affected by adjusting pH when sethoxydim or clethodim was applied with bentazon and Agrioil. Johnsongrass control over a pH range of 3.5 to 6.5 via the addition of glacial acetic acid and calcium hydroxide or ammonium hydroxide indicated a lack of pH dependence for these herbicides. The addition of ammonium hydroxide resulted in slight, but inconsistent increases in johnsongrass control.

In field experiments, chlorsulfuron and CGA 131036 did not injure winter wheat. Both herbicides applied postemergence at 9 and 10 g ai/ha completely controlled flixweed. CGA 131036 controlled cutleaf eveningprimrose 81%, and chlorsulfuron controlled 91%. At similar rates, CGA 131036 was also less effective than chlorsulfuron on henbit and Italian ryegrass. Both controlled wild buckwheat 77% when applied postemergence at 18 g/ha. Neither of the sulfonylurea herbicides controlled prostrate spurge or woolly croton as effectively as 2,4-D. In a bean root bioassay, root growth inhibition by both herbicides was partially alleviated by adding isoleucine and valine.

Soft red winter wheat cultivars were evaluated in field experiments in Georgia for tolerance to dicamba alone and mixed with 2,4-D. Treatments reduced ‘Florida 302’ yield more than ‘Florida 301’ or ‘Coker 983’ at Tifton in 1986. Mid-tillering Florida 302 wheat was more sensitive to treatment than fully tillered wheat. In 1987, dicamba plus 2,4-D applied at mid-tillering reduced yields of all cultivars in Watkinsville. Injury and yield reductions occurred primarily when mid-tiller treatments were applied to wheat that was planted 10 or 21 days later than recommended at Tifton or Watkinsville, respectively. When applied according to labeling, dicamba or dicamba plus 2,4-D use in Georgia soft red winter wheat can reduce grain yield.

A 2-yr study was conducted to evaluate the response of yellow starthistle density and grass biomass to combinations of newly seeded grass, picloram, and fertilizer. A combination of ‘Tualatin’ tall oatgrass or ‘Paiute’ orchardgrass with 0.14 or 0.28 kg ae/ha of picloram effectively controlled yellow starthistle and improved forage production. Grass seeded alone or combined with fertilizer neither controlled yellow starthistle nor improved forage production. Three-way combinations of grass, picloram, and fertilizer did not affect yellow starthistle density in either year but resulted in more ‘Tualatin’ tall oatgrass biomass in 1987.

Tolerance and subsequent yield response of established alfalfa, red clover, alsike clover, sainfoin, birdsfoot trefoil, and cicer milkvetch to sethoxydim and fluazifop spring applied and to hexazinone, metribuzin, and terbacil fall applied were determined in a field study. All legumes tolerated sethoxydim. Fluazifop was safe on all legumes except sainfoin. Alfalfa and cicer milkvetch tolerated hexazinone, metribuzin, and terbacil. Alfalfa dry matter yield was not affected by any of the herbicide treatments, but cumulative cicer milkvetch yield increased 9% over a 3-yr period with hexazinone applications. Sainfoin yield increased 20% with hexazinone and terbacil treatment. Hexazinone injured red clover and reduced yield. Alsike clover was the most susceptible legume to the residual herbicides. Weed dry matter yield associated with the legumes indicated that alfalfa and sainfoin were the most and the least competitive species, respectively. Plots treated with hexazinone contained the least amount of weeds, regardless of the legume species. Field peas seeded in rotation was not affected by herbicide residues; however, residues from terbacil applied at 1.0 kg/ha reduced seed yield of lentils.

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.

Interstate rights-of-way may serve as weed host reservoirs for the tarnished plant bug, an insect pest of cotton. Management of these rights-of-way may have an impact upon cotton pest management. In a 3-yr study, time of mowing, frequency of mowing, and sulfometuron methyl applied against overwintering rosettes influenced the cover of annual fleabane and wild carrot, which harbor tarnished plant bugs.

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.

The influence of spotted knapweed on surface runoff and sediment yield was determined under simulated rainfall conditions near Garrison, MT. Comparisons were made in 12 paired plots: one of each pair dominated by bunchgrass and the other dominated by spotted knapweed. Runoff and sediment yield were 56% and 192% higher, respectively, for the spotted knapweed, rather than the bunchgrass vegetation types. Spotted knapweed invasion onto bunchgrass range of western Montana is thus detrimental to the protection of soil and water resources.

The purpose of the research was to determine the effect of several postemergence herbicides on transpiration and growth of seedling oats and wheat. Fluazifop, haloxyfop, and sethoxydim were applied postemergence at various rates to oats and wheat in the 1- to 2-leaf stage in controlled environment rooms and the field. In all cases where transpiration was reduced significantly, oats were affected more than wheat. Generally, haloxyfop and sethoxydim in both controlled environments and the field suppressed oat growth more than wheat. Fluazifop controlled both small grain species equally in the field, but oats were suppressed more under controlled environment conditions. Effects of the three herbicides were always greater in the controlled environments than in the field.

Fluometuron at 1.1 kg ai/ha was applied postemergence (over-the-top) to cotton in the V3 to V4 stage to determine effects on flower and boll production, yield, and fiber quality. Treated plants produced more bolls but boll weight was reduced. Lint yield was not affected. Flower and boll production during the first 2 weeks of flowering were reduced, but treated plants produced more flowers and bolls during mid- and late bloom. A delay in sympodia development delayed development of fruiting structures. Fluometuron treatment promoted sympodia development on monopodia at nodes three and four. Fiber micronaire was reduced in 1 of 2 yr. Fiber strength, length, and length uniformity were not affected.