Wild oat (Avena fatua L.) competition severely reduced flaxseed (Linum usitatissimum L.) yield. Averaged over two locations and two fertility levels, 80 wild oat plants/sq yd reduced the yield 9.4 bu/A (60.1%) in 1964 and 160 wild oat plants/sq yd reduced the yield 21.5 bu/A (82.1%) in 1965. At Fargo, 160 wild oat plants/sq yd reduced flaxseed yield 16.1 bu/A (86.1%) in 1966. Flaxseed yield components, including bolls/sq ft, seeds/boll, plants/sq ft, and weight/1000 flaxseed were determined. Although all components were reduced by wild oat competition, a reduction in the number of branches and flax bolls/sq ft accounted for 90.7% of the yield loss. A reduction in weight/1000 seed and the number of flax plants/sq ft contributed 7.0% and 4.6% to the yield loss, respectively. Competition from wild oat also reduced flaxseed quality. The percent oil was reduced in all 3 years of the experiment. Iodine number of the oil was reduced, primarily because of an increase in oleic acid and a decrease in linolenic acid.

Dormancy, longevity, and germination of seed of tall larkspur (Delphinium barbeyi Huth), duncecap larkspur (Delphinium occidentale S. Wats.), low larkspur (Delphinium nelsonii Greene), and western false hellebore (Veratrum californicum Durand) were investigated. Field studies were conducted in the Cache National Forest in Idaho at 8,000 ft elevation. With the exception of 12 of 400 buried duncecap larkspur seed, seed of all species in the longevity study germinated or disintegrated the first year under field conditions. No sound or viable seed was found at the end of the second year. Dormancy of most seed was broken in 13 to 19 weeks when seed were held at 33 to 34 F in moist sand in the laboratory or when seed were in contact with moist unfrozen soil under snow. Under optimum field conditions, the majority of the seed germinated by late March. Seedlings were well-established before snow-melt in June.

The herbicides, S-ethyl hexahydro-1 H-azepine-l-carbothioate (molinate) applied preemergence and 3′,4′-dichloropropionanilide (propanil) applied as a contact spray at several dates, were evaluated for control of barnyardgrass (Echinochloa crusgalli (L) Beauv.) in water-seeded rice (Oryza sativa L., var. Caloro) flooded continuously to a shallow (3 inch) depth. Propanil applied when barnyardgrass had 6 to 9 inches of leaves exposed gave higher yields than earlier or later applications. Molinate gave the best barnyardgrass control when it was applied as a granule, incorporated, and applied onto dry soil. Molinate controlled the three major phenotypes of barnyardgrass. Germinating barnyardgrass seed were severely inhibited in growth by molinate concentrations greater than 0.3 ppm while germinating rice seed were not inhibited until the concentrations were greater than 5 ppm. Low concentrations of molinate stimulated shoot growth of both rice and barnyardgrass.

A survey of the phytophagous insect fauna of Russian thistle (Salsola kali L., var. tenuifolia Tausch) showed that this weed serves as an alternate feeding and/or breeding host to a number of economically important insects in southern California.

The translocation of 2-methoxy-3,6-dichlorobenzoic acid (dicamba-7-14C) in purple nutsedge (Cyperus rotundus L.) at different stages of development and under various light regimes was studied using autoradiography and liquid scintillation counting techniques. The fate of the herbicide was investigated by means of thin-layer chromatography. Dicamba was slowly but appreciably translocated in purple nutsedge following application to the leaves or roots. Foliarly applied dicamba movement proceeded both acropetally and basipetally, and the herbicide became widely distributed throughout the aerial parts of the plant and accumulated in the regions of meristematic activity. Dicamba was barely detectable in the underground organs, although it was excreted into the culture medium and passed through the rhizomes and tubers into daughter plants. Root-applied dicamba distribution was general throughout the plant except within the tubers and the tips of the leaves. Dicamba was barely detectable within the tubers, although it was present in quantity at or near the surface. Dicamba accumulation was evident at the tips of the leaves. Translocation was enhanced under low light conditions. Distribution of dicamba was profoundly affected by the stage of development of the plant. Greater translocation and broader distribution of the herbicide occurred in the vegetative stage of development. After flowering, movement out of the treated leaf decreased. Studies indicated that the herbicide was not degraded by the plant during the 10 days following treatment.

Rates of 0 and 5 lb/A of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) or 2-chloro-4,6-bis(ethylamino)–s-triazine (simazine) were combined with O and 200 lb/A of nitrogen fertilizer as preemergence applications on plots planted to corn (Zea mays L., var. Mo. 880) in May of 1964 and 1965. Soil samples collected in December, 1965, and again in February, 1966, were plated on Difco potato dextrose agar and nutrient agar to determine the growth of fungal and bacterial colonies. There was no difference in the total number of fungal colonies grown on media seeded with soils from the field studies, yet variation in individual species occurred. The number of bacterial colonies increased on plates seeded with soil from plots treated with 200 lb/A of nitrogen plus 5 lb/A of simazine but not from simazine-treated soil without nitrogen.

Wild oat (Avena fatua L.) competition increased the losses in yield of both wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) with increased densities of seedlings. At Fargo in 1965, wild oat densities of 70 and 160 seedlings/sq yd reduced the wheat yield 22.1% and 39.1%, respectively, compared to the wild oat-free check. Similar wild oat densities reduced the barley yield 6.5% and 25.9%, respectively. The addition of nitrogen and phosphorus fertilizer reduced the yield loss caused by wild oat 2 out of 3 years of the experiment. Although a considerable yield reduction occurred in barley and wheat, percent protein and seed size were not influenced noticeably.

The differential phytotoxicity of an unidentified amiben conjugate (hereinafter referred to as amiben-X), obtained from giant foxtail (Setaria faberii Herrm.) treated with 3-amino-2,5-dichlorobenzoic acid (amiben) was tested in several plant species. Concentrations of amiben-X up to 10 ppm had no effect on radicle elongation in seedlings of soybean (Glycine max (L.) Merr.) or ivyleaf morningglory (Ipomoea hederacea (L.) Jacq.). Giant foxtail radicles were inhibited about 35% at 10 ppm. Amiben, amiben-X, and N-(3-carboxy-2,5-dichlorophenyl)-glucosylamine (hereinafter referred to as N-glucosyl amiben) were detected in seedling tissues of the three above species treated for 24 hr with 20 ppm amiben-X. The growth response of the plants to amiben-X probably resulted from the action of the amiben released by plant hydrolytic activity on amiben-X; amiben-X itself is considered to be relatively nonphytotoxic.

Wild oat (Avena fatua L.) was removed at several stages of growth from flax (Linam usitatissimum L.) plots in 1964, 1965, and 1966. The flaxseed yield was reduced as the period of competition increased during each year. In 1965, competition from wild oat until the 4 to 5-leaf stage reduced the flaxseed yield 15.1% while competition until maturity reduced the yield 74.9%. The number of bolls/sq ft also was reduced as the period of competition increased; but the number of seed/boll, plants/sq ft, and the weight/1000 seed were not affected consistently by wild oat competition. Both the percent oil of flaxseed and the iodine number of the oil were reduced by wild oat competition, but not until the wild oat was in the heading stage and the flax was in the boll stage.

A shielded, tractor-mounted sprayer for research plots is described. Advantages of this sprayer for research plots are reduced spray drift, rapid and thorough cleaning between herbicide treatments, adequate mixing of herbicide suspensions, rapid and accurate herbicide application, and facilitating plots large enough to take yield data with a combine.

The phytotoxicities of soil-incorporated 2,6-dichlorobenzonitrile [dichlobenil] and 2,6-dichlorothiobenzamide [hereinafter referred to as SD-7961] were compared in five soils in the greenhouse. Dichlobenil and SD-7961 were about equally toxic to snap beans (Phaseolus vulgarus L., var. Black Valentine) in each of the five soils. The herbicides were more toxic in Christiana loam than in the other four soils. Phytotoxic residues of both herbicides disappeared most rapidly from Hagerstown silty clay loam and Christiana loam and least rapidly from Sharkey clay. Gas chromatographic analyses of soil extracts confirmed that dichlobenil was most persistent in the clay. Small amounts (0.14 ppmw or less) of 2,6-dichlorobenzoic acid [hereinafter referred to as 2,6-DBA] were detected in soil from greenhouse pot cultures about 9 months after incorporation of dichlobenil. In a field experiment at Beltsville, Maryland, residues of dichlobenil persisted from one season to the next but did not build up in soil sprayed annually for 3 years with 4 or 8 lb/A. Some movement from the surface 6 in into the 6 to 12-in zone occurred on plots sprayed 2 years in succession with 8 lb/A or once with 40 lb/A. Rapid loss of dichlobenil occurred during summer months. When the concentration of dichlobenil on the 40-lb/A plots dropped to about 10%, subsequent loss occurred at a very slow rate.

Root applications of 9.0 μM 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) to soybean plants (Glycine max (L.) Merr., var. Chippewa) for 4 hr significantly reduced their transpiration rates. Similar reductions in transpiration rate were elicited by foliar applications of 900 μM. All atrazine treatments that reduced transpiration prevented dry weight accumulation by the plants and increased plant hydration. Root additions of glucose to de-rooted plants treated with atrazine had no influence on the transpiration reduction due to atrazine treatment but caused an increase in dry weight accumulation. There was a rapid accumulation of 14C-atrazine in the roots of the soybean plants from the culture solution with subsequent movement to the leaves. Leakage of 14C-atrazine out of the roots into the water medium after treatment termination was observed.

Seed of corn (Zea mays L., var. Texas 28) and cotton (Gossypium hirsutum L., var. Deltapine smooth leaf) were planted in sand and subsequently drenched with solutions of α,α,α trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin). The levels of herbicide used inhibited growth of roots and shoots in both crops, but cotton proved more tolerant than corn. The roots failed to elongate normally, but the lateral growth that continued gave the radicle a “club-shaped” appearance, especially in corn. Stained sections of the roots were mounted as permanent slides for study. The cells at the extreme tip of the treated roots were small and dense; many were multinucleate. Immediately behind this region, the cells were abnormally large, thin-walled, and aberrant. A disorganized type of nuclear division was evident. Cell plate and cell wall formation were apparently rare. Although we found no normal sequence of mitosis in cells of treated roots, all stages of mitosis were seen in the untreated roots.

The effects of temperature and the annual growth cycle on the formation of root suckers were determined by propagating root cuttings of black locust (Robinia pseudoacacia L.). The percentage of cuttings which formed suckers in an air temperature of 60 F was significantly lower than that of cuttings at 70 to 80 F. In the annual growth cycle experiment, cuttings removed in June formed significantly fewer suckers than those removed during January, March, August, or November.

Herbicides were mixed with Drummer silty clay loam soil in 1-inch layers in the shoot, root, shoot and root, or seed zones for giant foxtail (Setaria faberii Herrm.). After 2 weeks in the greenhouse, foxtail tops were harvested and dry weights used as the measure of herbicidal effectiveness. All of the 11 herbicides evaluated caused a reduction in dry weight when placed in the shoot zone. When placed in the root zone, only 3-amino-2,5-dichlorobenzoic acid (amiben) caused a reduction in dry weight. Most herbicides were just as effective, or more so, in the shoot zone as in the seed zone. Only amiben and N-1-naphthylphthalamic acid (NPA) were more effective in the seed zone than in the shoot zone.

The fate of the potassium salt of 2,4-dichlorophenoxyacetic acid (2,4-D) when applied to birdsfoot trefoil (Lotus corniculatus L., var. Viking) and an intercross resistant to 2,4-D was studied. No difference in spray retention per mg fresh weight between the two trefoils was detected and more than 98% of 2,4-D-2-14C was absorbed within 2 days after application. Herbicide moved from treated leaves to young leaves, stems, and roots in about equal quantities. Seven days after treatment, 70% of the 14C activity of 2-propanol extracts of both trefoils was 2,4-D-2-14C; the remaining activity of the extract was from unknown metabolites of 2,4-D. The total activity recovered from the tolerant selection and Viking, respectively, was 57% and 50% of that applied. The methods used failed to establish a clear basis for the difference in reaction of the two birdsfoot trefoils to 2,4-D.

Barnyardgrass [Echinochloa crusgalli (L.) Beauv.], duck-salad [Heteranthera limosa (Sw.) Willd.], hemp sesbania [Sesbania exaltata (Raf.) Cory], and northern jointvetch [Aeschynomene virginica (L.) B.S.P.] significantly reduced rice [Oryza sativa L.] yields. Damage to rice increased as populations of barnyardgrass, hemp sesbania, and northern jointvetch increased. Barnyardgrass and duck-salad lowered yields during early season, but hemp sesbania and northern jointvetch decreased yields in late season.