Fluridone {1-methyl-3-phenyl-5-[3-(trifluromethyl)phenyl]-4(1H)-pyridinone} and norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone] inhibited carotenoid synthesis in wheat (Triticum aestivum L. ‘Maricopa’) seedlings and caused the accumulation of colorless carotenoid precursors, phytoene, and phytofluene. These data suggested that dehydrogenation reactions following phytoene formation were inhibited by the herbicides. Chlorophyll accumulated in the treated seedlings grown under 10 lux of light but was destroyed in seedlings illuminated with 16 klux of light. Seedlings illuminated with 16 klux of light lacked chloroplast ribosomes and normal ultrastructure whereas dark grown seedlings contained pastid ribosomes and had normal etioplast ultrastructure. The disruption of the chloroplasts and loss of chlorophyll was due to the absence of carotenoids in the treated plants, which would normally act to protect the chloroplasts from photodestruction.

The herbicide 2,4-D [(2,4-dichlorophenoxy)acetic acid] was applied as sublethal rates to sugarbeets (Beta vulgaris L. ‘Mono Hy D2’) in the field at different growth stages to determine its effect on growth and yield. The greatest reduction in top growth occurred when the highest rate of 2,4-D, 0.07 kg/ha, was applied to the oldest plants (12-leaf stage). All rates of 2,4-D reduced the components of sucrose yield (percentage sucrose, percentage purity, and root weight) to the extent that, together, the three components contributed to a significant reduction in recoverable sucrose. The yields of recoverable sucrose were reduced 6.8, 7.8, and 13.2% by the 0.017, 0.035, and 0.07 kg/ha rates, respectively.

Seed of yellow foxtail (Setaria lutescens (Weigel) Hubb.) biotypes collected in Connecticut, Iowa, Massachusetts, Pennsylvania, and California were grown under field conditions at Davis and Woodland, California. Three biotypes collected in California alfalfa (Medicago sativa L.) fields all exhibited only a prostrate growth habit; the biotypes from the eastern United States all had an upright growth habit. The California biotypes were always glaucous; those collected in the east were not glaucous. Ratio of culm height to culm length were near unity for the eastern biotypes but averaged 1.5 to 1.7 for the California biotypes. Variations existed between biotypes in days from planting to heading, number of nodes per culm, leaf shape and size, and in final dry weight per plant.

At Hilario Ascasubi, Argentina, and Prosser, Washington, EPTC (S-ethyl dipropylthiocarbamate) was injected in sandy soil as two lines 5 cm deep and 6 cm apart. At 2 kg/ha (assuming the treated area was 12 cm wide), EPTC controlled 95 to 100% of foxtail millet [Setaria italica (L.) Beauv.] in a band 13 to 14 cm wide without significant injury to alfalfa (Medicago sativa L.) seeded 1.5 cm deep midway between the two lines of herbicide. At 3 and 4 kg/ha, EPTC sometimes injured alfalfa, but only temporarily, and at 1 kg/ha, it controlled 75 to 100% of the millet in a band 11 to 12 cm wide. Where alfalfa is seeded in rows, especially for seed production, subsurface line injection of EPTC could provide effective, efficient, and economical selective control of certain annual weeds.

A collection of common purslane (Portulaca oleracea L.) ecotypes from various locations around the world was assembled at the University of Illinois. Applications of nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) to the various ecotypes showed that 3 of the 26 ecotypes [India, Mexico, and Florida (Sanford)] exhibited some degree of tolerance. This marginal tolerance rapidly disappeared as the rate of nitrofen increased beyond 0.56 kg/ha. All of the ecotypes tested were susceptible to applications of oxyfluorfen [2-chloro-2-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene]. Oxyfluorfen was toxic to common purslane plants at rates as low as 5 g/ha. Treatment of ‘Hybelle’ (tolerant) and ‘Rio Verde’ (susceptible) cabbage (Brassica olerace var. capitata L.) cultivars with 3.36 kg/ha nitrofen reduced plant fresh weight to 82% and 62%, respectively, of control. Oxyfluorfen at 0.15 kg/ha reduced fresh weight to 60% and 27% for Hybelle and Rio Verde, respectively. Applications of nitrofen at 3.36 kg/ha reduced plant fresh weight in Hybelle the same amount as 100 g/ha oxyfluorfen and 70 g/ha in Rio Verde.

The uptake, distribution, and metabolism of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] by sugarcane (Saccharum officinarum L.) cultivars ‘PR980’ and ‘PR1048’ were determined 3 and 10 days after root treatment with 18.4 μM 14C-ring-labeled diuron. Uptake and distribution did not account for the differential tolerance of the two cultivars to diuron. Concentration of unmetabolized diuron was higher in the shoot and root of susceptible cultivar PR1048 than in tolerant cultivar PR980 at 3 and 10 days after treatment. The predominant metabolic pathway for diuron metabolism in both susceptible and tolerant sugarcane cultivars appeared to be the formation of mono-methyl diuron and its conjugation. The metabolic process was more rapid in PR980 than PR1048, apparently accounting for the tolerance of PR980.

The effect of calcium and nitrogen level on the uptake of linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] from nutrient solution by soybean [Glycine max (L.) Merr.] seedlings was determined and related to root membrane fatty acid composition. Calcium levels in the nutrient solution were 0.4, 4.0, or 8.0 mM and nitrogen levels were 4.0, 16.0, or 32.0 mM with the pH adjusted to 6.5. As calcium concentration increased, linuron uptake decreased. The reverse was true for nitrogen. These changes were not related to transpiration. Increasing calcium concentration increased palmitic acid and decreased linolenic acid in the plasmalemma of the soybean roots resulting in a greater degree of saturation. Nitrogen likewise increased the degree of saturation in the plasmalemma, but the effect was mainly seen in the balance between stearic and linoleic acids. In the mitochondria, however, the trends were inconclusive. High levels of linolenic acid were observed in the mitochondria regardless of treatment.

Two applications of benefin (N-butyl-N-ethyl-α,α,α,-trifluoro-2,6-dinitro-p-toluidine), profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine], prosulfalin N-[[4-(dipropylamino)-3,5-dinitrophenyl]sulfonyl]-S,S-dimethylsulfilimine, and napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] provided full-season large crabgrass [Digitaria sanguinalis (L.) Scop.] control in turfgrass. Benefin was applied at 3.3 kg/ha in March and 2.2 kg/ha in May while other herbicides were applied at 2.2 kg/ha in March and May. Satisfactory goosegrass [Eleusine indica (L.) Gaertn.] control was obtained with a single March treatment with prosulfalin, but two applications of napropamide in March and May were required for similar control. None of the herbicide treatments severely injured common bermudagrass [Cynodon dactylon (L.) Pers.] or Kentucky bluegrass [Poa pratensis (L.) ‘Common’] in these studies. Prosulfalin at 6.6 kg/ha applied as single treatment or 3.3 kg/ha in each of two applications resulted in moderate injury to Kentucky bluegrass in 1 of 2 yr.

The antidote R-25788 (N,N-diallyl-2,2-dichloroacetamide) protected corn (Zea mays L. ‘DeKalb 315A’) seedlings from injury caused by the acetanilide herbicides, alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], H-22234 [N-chloroacetyl-N-(2,6-diethylphenyl)glycine ethyl ester], and H-26910 [N-chloroacetyl-N-(2-methyl-6-ethylphenyl)glycine isopropyl ester] in a greenhouse study. R-25788, however, did not protect four weed species tested. R-25788 only partially protected corn from injury caused by acetochlor [2-chloro-N-(ethoxymethyl)-6′-ethyl-o-acetotoluidide]. R-25788 was an effective antidote whether applied preemergence, preplant-incorporated, or as a tank mix. Injury symptoms caused by EPTC (S-ethyl dipropylthiocarbamate) and the acetanilide herbicides were similar; both caused leaf twisting and rolling, and at high rates leaves failed to emerge through the coleoptile.

Wettable powder and granular formulations of pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide], applied at 1.7 kg/ha to the soil surface or incorporated to depths of 1.3 to 7.5 cm, controlled dodder (Cuscuta indecora Choisy and C. campestris Yunck.) completely in the greenhouse for periods of 6 to 16 weeks. Seedlings emerged in pronamide-treated soil, but did not elongate normally and did not twine. Pronamide had very little activity as a vapor. In the field, the same rate applied to the soil surface and sprinkler irrigated or mechanically incorporated with the soil usually controlled dodder for about 1 month longer than did the standard herbicide, chlorpropham (isopropyl m-chlorocarbanilate) at 6.7 kg/ha. Pronamide at 6.7 kg/ha did not injure established alfalfa (Medicago sativa L.).

Control of field bindweed (Convolvulus arvensis L.) on irrigated land was studied by application of herbicides once in the fall and then only in the spring for the next 4 yr. Control of field bindweed 8 months after a fall application of 2.2 kg/ha of dicamba (3,6-dichloro-o-anisic acid) or 3.4 kg/ha of 2,4-D [(2,4-dichlorophenoxy)acetic acid] was 90 and 83%, respectively. Spring applications of 0.28 kg/ha of dicamba, 0.56 kg of 2,4-D, or the mixture of these two herbicides suppressed the growth of field bindweed similarly each year. By the fall of the fourth year, field bindweed covered an average of 9% of the soil surface in the plots that received both fall- and spring-applied herbicide treatments, 72% in plots that received only fall-applied herbicide treatments, and 80% in the untreated plots. Yield of corn (Zea mays L. ‘Pioneer 3306’) was significantly higher in all treated plots than in the untreated check plots in 1 out of 2 yr. Yield of sorghum [Sorghum bicolor (L.) Moench ‘Pioneer 833’] was not increased significantly in any treated plots, but in 1 yr the mixture of 0.28 kg/ha of dicamba plus 0.56 kg/ha of 2,4-D reduced yield significantly when this mixture was applied twice at these same rates in the spring.