Rush skeletonweed (Chondrilla juncea L.), a serious agricultural pest in Australia, is increasing in the western United States. Persistence in established areas is encouraged by the resprouting of all portions of the taproot and wind borne achenes. Invasion to new areas is reduced by short achene life, the germination pattern of young seedlings, and the lack of shade tolerance. Fall applied 4-amino-3,5,6-trichloropicolinic acid (picloram) and 2-methoxy-3,6-dichlorobenzoic acid (dicamba) were effective for chemical control of spot infestations.

Herbicidal residues in water and soil were determined after treating eight ponds with six herbicides. Relatively high concentrations of 2,6-dichlorobenzonitrile (dichlobenil), 2,3,6-trichlorophenylacetic acid (fenac), and 2,4-dichlorophenoxyacetic acid (2,4-D) were present in the upper 1-in of the hydrosoil following treatments with granular formulations of these herbicides. Fenac and dichlobenil residues persisted in both water and soil for periods exceeding 160 days. Low concentrations of 2,4-D were found in water for 24 days and in the soil for 55 days following treatment. The mono-N,N-dimethylcocoamine salt of 7-oxabicyclo(2.2.1)heptane-2,3-dicarboxylic acid (amine salt of endothall), 1,1′-dimethyl-4,4′-bipyridinium salt (paraquat), and 6,7-dihydrodipyrido(1,2-a:2’,1′-c)-pyrazidiinium salt (diquat) were relatively less persistent in water and were no longer found after 24, 8, and 4 days, respectively. However, paraquat and diquat were held by the hydrosoils and persisted in high concentrations for more than 85 and 160 days, respectively. In ponds with dense weed infestations, a large fraction of the herbicide may be held by the plants for some time.

The responses of herbicides applied singly are used in calculating the “expected” response when they are combined. The expected response for a combination is obtained by taking the product of the percent-of-control values for herbicides applied alone and dividing by (100)n-1 where n is the number of herbicides in the combination.

Several herbicides were used for control of weeds in Jersey Orange sweet potato plantings on a sandy loam soil at Hammonton, New Jersey, during 1960, 1961, and 1962. The treatments were applied preemergence to the weeds at transplanting of the crop. Data included crop injury scores, level of weed control, effects on yield, influence on internal root color and flavor, and effects on sprouting.

Excellent control of germinating annual weeds was obtained with 3-amino-2,5-dichlorobenzoic acid (amiben), 2,6-dichlorobenzonitrile (dichlobenil), N,N-dimethyl-2,2-diphenylacetamide (diphenamid), and dimethyl 2,3,5,6-tetrachloroterephthalate (DCPA). These herbicides had no adverse effects on yield, quality factors, or growth.

The toxicity, adsorption, and leaching of four herbicides in different soils were determined by a method based on a sensitive root bio-assay which appeared suitable for herbicides affecting root growth. The rate of leaching of the herbicides was determined by measuring the herbicidal effect of the leachate obtained from three heights of soil columns. The same bio-assay was utilized for testing the extent of inactivation of herbicides due to adsorption by soil. In this case, mixtures of various rates of soil with silica sand were used as cultures for the bio-assay.

A soil column system for determination of relative movement of herbicides in soils is described. A data presentation system which expresses the results for each herbicide in a given soil as a single number is proposed. Comparisons of mobilities of new herbicides with those known for other older, better understood herbicides should make it possible to predict the behavior of new herbicides in the field. The aromatic acid herbicides were most mobile, and the insoluble toluidines least mobile. Results for 28 herbicides are presented.

This work is an endeavor to aid researchers located in remote areas as well as researchers who may have experienced difficulties in the regulation of controlled environment chambers. Descriptions of the maintenance and use of controlled environment chambers contained herein were compiled over an 8-year period of experience with four chambers. Although the physical characteristics of the controlled environment chambers described are dissimilar from many, the causes and remedies of malfunctions are general and typical of those found in many controlled environment chambers. Several protective devices for expensive equipment are described as well as several common malfunctions and their remedies.

Two morphological types of tubers of yellow nutsedge (Cyperus esculentus L.) were collected over a 2-year period and were sprouted in the laboratory. Tuber dormancy occurred during late summer and early fall. Sprouting was highest during the winter and spring. Mechanical disturbance of the nutsedge stand increased tuber sprouting. Available carbohydrates followed a pattern similar to sprouting; minimum levels were found during late summer. The two types of tubers appeared to be similar in respect to the characteristics studied.

Treatments made at 2-week intervals on guava (Psidium guajava L.) with a 1:1 ratio of butoxyethanol esters of 2,4-dichlorophenoxyacetic acid:2,4,5-trichlorophenoxyacetic acid (2,4-D:2,4,5-T) have shown it to be more susceptible when treatments are made during the wet season than during the dry season. Greater susceptibility is related to a plant condition characterized by many new leaves but little or no terminal twig elongation. A similar pattern of defoliation response is caused by 2-methoxy-3,6-dichlorobenzoic acid (dicamba) and 2,3,6-trichloropicolinic acid (picloram) as by 2,4-D:2,4,5-T, but the period of maximum susceptibility based on defoliation percentages 1 year after treatment occurred later in the season.

Heights of corn and giant foxtail (Setaria faberii Hermm.) were measured during 1963, 1964, and 1965 in east-central Illinois to establish guidelines for postemergence control of this weed in corn. With an average planting date of May 9, corn grew to a height of 6 in and foxtail 2 in by May 28. With corn growing at a daily rate of 1 in and foxtail ½ in from June 5 to 20, foxtail height was 40 to 45% that of corn.

Environmental and physical factors influencing the effectiveness of preemergence applications (4 lb/A) of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) were evaluated under field conditions for 10 Hawaiian sugar cane (Saccharum officinarum L.) plantations. Rainfall, soil pH, organic composition, time lapse between field harvest and herbicide application, and maximum temperature had a significant effect on the resultant period of weed control. The data from 295 field tests conducted over a 10-year period then were subjected to multiple regression analysis. The prediction equation derived via these calculations was sufficiently accurate to justify its application to the Hawaiian sugar cane regions. The single most important factor adversely influencing the preemergence activity of diuron was the lapse of time between harvest and application, a factor within the control of the plantation personnel.

Under controlled conditions in a growth chamber, emergence of tumblegrass (Schedonnardus paniculatus (Nutt.) Trel.), redroot pigweed (Amaranthus retroflexus L.), and barnyardgrass (Echinochloa crusgalli (L.) Beauv.) was best with an 8-hr night temperature of 65 F and a 16-hr day temperature of 80 F. Other temperature ranges, in order of decreasing effectiveness in stimulating emergence, were 80–95, 50–65, and 35–50 F. Best emergence occurred at the ½-in depth of planting followed by 14, 1, 2, and 4 in. Barnyardgrass was the only weed that emerged appreciably from the 4-in depth. Average emergence was better on a coarse-textured soil than on a fine-textured soil. Under dry soil conditions, emergence was reduced by soil crusting.

To evaluate the effect of different soil moisture levels on the phytotoxicity of soil applications of arsenic trioxide (As2O3), water and alcohol extractable soil arsenic (As) data were related to the growth and development of 4-month-old Monterey pine (Pinus radiata D. Don.) in greenhouse soil cultures. Also, various rates of As2O3 and water were applied to the surface of soil columns to determine the effective penetration of soluble As. Under normal moisture regime, 8000 lb/A of As2O3 were required for high phytotoxicity on a Chenango silt loam, with excessive moisture resulting in an increase in this phytotoxic effect. With water and alcohol extraction procedures, an adequate range of values was obtained in relation to the total As2O3 rates and plant responses. Lethal concentrations of As in the soil columns were limited to the surface 3 in depth in the silt loam.

Two fish from South America. (Metynnis roosevelti Eigenmann and Mylossoma argenteum E. Ahl.), both called silver dollar fish, grazed rapidly on several species of submersed aquatic weeds. Horned pondweed (Zannichellia palustris L.), American pondweed (Potamogeton nodosus Poir.), and sago pondweed (Potamogeton pectinatus L.) were most palatable to the fish. Richardson pondweed (Potamogeton richardsonii (Ar. Benn.) Rydb.), curlyleaf pondweed (Potamogeton crispus L.), and American elodea (Elodea canadensis Michx.) also were grazed. The fish readily grazed on shoots of all sizes except those of mature plants. The Mylossoma grazed the plants more rapidly than the Metynnis. When water temperatures were above 70 F, the fish became more active in their feeding habits.

A field study was made on the competitive effect of quackgrass (Agropyron repens (L.) Beauv.) on corn for the nutrients N, P, and K during 1962 and 1963. Quackgrass competition drastically reduced corn height and yield and delayed maturity. High levels of fertilization did not overcome the effects of quackgrass competition. The annual uptake by quackgrass during the growing seasons of 1962 and 1963 was 105, 15 and 60 lb/A of N, P, and K, respectively. Quackgrass shoots harvested at maturity in mid-July had taken up 55, 45, and 68% of the total N, P, and K, respectively, that was removed throughout the season by quackgrass shoots plus rhizomes. It appeared that the early season uptake of N and K by quackgrass may have contributed to, but was not solely responsible for, the reduction in corn height and yield and delayed maturity noted later in the season.

Experiments were conducted on black locust (Robinia pseudoacacia L.) to determine the effect of auxin distribution and degradation on the formation of root suckers. Stump sprouting and root suckering occurred when black locust seedlings were decapitated, and the presence of stump sprouts prevented root suckering. The influence of stump sprouts could be replaced by applying indoleacetic acid (IAA) in lanolin paste to the cut surfaces of root stubs. These results provide additional support for an apical dominance theory of suckering. When IAA-2-C14 in lanolin was applied to the cut surfaces of root stubs, autoradiographs showed that C14 activity was concentrated where the majority of root suckers normally would develop. Apparently, IAA accumulated in this region and inhibited root suckering. When the IAA-lanolin paste was removed from the root stubs after inhibiting suckering for a month, vigorous root suckering took place. This indicated the possibility that black locust roots contain an IAA oxidase system. The existence of such a system was demonstrated by dialyzed enzyme preparations extracted from black locust roots which oxidized IAA in a Warburg apparatus.

The effect of a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) on the growth of cotton seedlings was studied under greenhouse conditions as influenced by dosage, 0.25, 0.5, 0.75, and 1.0 lb/A, and depth of soil-incorporation, 0 to 6 in in 0.5-in increments; the cotton seed were planted 1.5 in deep and watering was by subirrigation.

Trifluralin caused stunting in height of cotton seedlings and prevention of lateral root growth. The dosage of the chemical influenced the degree and persistence of stunting more than did depth of incorporation. Marked stunting occurred at 1 lb/A at all depths of incorporation and persisted for the duration of the experiments, about 1 month; slight to moderate stunting occurred at 0.75 lb/A or less but was of short duration, 1 to 2 weeks. Lateral root growth was affected more by depth of incorporation than by dosage; though the growth of the taproot was essentially unaffected, the growth of lateral roots was completely prevented by even the lowest dosage applied, 0.25 lb/A, incorporated to the greatest depth, 6 in. Root growth was prevented only along that portion of the taproot growing in treated soil; when trifluralin was incorporated above the seed, root development was unaffected. Stunting occurred independently of the effect on root growth.

The quantities of chloroplast proteins and chlorophyll were lower in oat plants treated 6 days with 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) than in the controls. Radioactive amino acid incorporation into chloroplasts indicated that the reduced levels of protein resulted from reduced synthesis. Glucose improved the amino acid incorporation in the treated tissue, but still the rate was reduced markedly by the simazine treatment. An effect of simazine even in darkness on amino acid incorporation into chloroplasts was suggested by the data. Total ribonucleic acid (RNA) content and synthesis as measured by incorporation of p32 were altered by simazine treatments.

Spring and fall applications of 10 soil sterilant herbicides were investigated for control of brush and herbaceous vegetation at five locations in Texas. A majority of the herbicides controlled most brush species. However, 5-bromo-3-sec-butyl-6-methyluracil (bromacil), 2-methoxy-4,6-bis(isopropylamino)-5-triazine (prometone), and 4-amino-3,5,6-trichloropicolinic acid (picloram) were most effective at all locations. A mixture of disodium tetraborates, 3-(p-chlorophenyl)-1,1-dimethylurea (monuron) and trichlorobenzoic acid was very effective for at least 20 months at four of the five locations. Most herbicides controlled herbaceous vegetation for 1 year or less. Bromacil controlled herbaceous vegetation for approximately 2 years at most locations.

Rhizome differentiation in yellow nutsedge (Cyperus esculentus L.), cultured under 12½, 14, and 15½-hr photoperiods, 21–16, 27–21, and 33–27 C temperatures (day and night, respectively), Hoagland solutions of 1/32, 1/8, and 1/2 strength nitrogen (N), and 0, 10, and 1000 ppm gibberellin (GA), was investigated in controlled-environment chambers.

High levels of N, long photoperiods, and high levels of GA at the shortest photoperiods inhibited tuberization whereas high temperatures at the lowest N level favored tuberization. Shoot formation was promoted by high levels of N, long photoperiods, and high temperatures under 12½ and 14-hr photoperiods while GA had a retarding effect. The higher levels of N, temperature, and GA decreased carbohydrate level whereas the longer photoperiods increased it.

It may be concluded that tuberization is not only the result of surplus carbohydrates in the plant but is controlled also by some GA-like substances regulated in the plant under specific conditions of photoperiod and temperature.