In undrained soil or solution cultures of oats or barley, the effects of hours of exposure and concentration of 2,2-dichloropropionic acid (dalapon) on height and fresh weight were equivalent. Dalapon was shown to be a growth inhibitor in corn coleoptile and pea stem sections but was inactive in oat coleoptile sections. Dalapon was antagonistic to IAA induced growth in corn coleoptile sections and 2,4-D induced growth in pea stem and oat coleoptile sections. The antagonism was reversible in pea and oat tissue, but was competitive in pea stem sections. Dalapon was shown to be an anti-auxin.

For the control of wild garlic in Missouri in comparison with 2,4-dichlorophenoxyacetic acid (2,4-D) during 1954–1960, 3-amino-1,2,4-triazole (amitrole), sodium 2,2-dichloropropionate (dalapon), maleic hydrazide (MH), 2,3,6-trichlorophenylacetic acid (fenac) and 2,3,6-trichlorobenzoic acid (2,3,6-TBA) were effective. 2,3,6-TBA alone was more effective than 2,4-D. The toxicity of 2,3,6-TBA was increased by addition of a wetting agent. Heavy spot treatments of wild garlic with 2,3,6-TBA killed the established plants, but did not eradicate wild garlic because of sprouting of dormant bulbs.

Repeated applications of amine methylarsonate over a two year period resulted in significant reductions in nutsedge tuber numbers at 1.3, 2.6 and 3.8 ounces per 1000 sq. ft. Single annual applications of amine methylarsonate at the same rates were ineffective. Amine methylarsonate and disodium monomethylarsonate treatments gave moderate reductions in nutsedge tuber numbers in thin Bermudagrass turf after one season.

Mixed stands of big sagebrush (Artemisia tridentata Nutt.) and green rabbitbrush (Chrysothamnus viscidiflorus (Hook.) Nutt.) were sprayed with butyl ester of 2,4-dichlorophenoxyacetic acid (2,4-D) at 1, 2, 3, and 4 lb/A on six phenological dates in 1956, 1957, and 1958 at the Squaw Butte Experiment Station, Burns, Oregon. Data on soil moisture; soil temperature; growth development of herbaceous species; twig elongation of big sagebrush and green rabbitbrush; dry-matter, crude-protein, and total-carbohydrate contents of green rabbitbrush herbage; and crude-protein and total-carbohydrate contents of big sagebrush and green rabbitbrush roots were obtained at weekly to biweekly intervals in all 3 years to evaluate the ecological and physiological conditions that might indicate seasonal patterns of susceptibility to 2,4-D. Big sagebrush, a non-deciduous, non-sprouting plant, was easily killed with 2,4-D at 2 lb/A when soil temperatures and moisture contents were satisfactory for vigorous growth. The development of abundant leaf area on green rabbitbrush, a deciduous, sprouting plant, was important for spray interception and a photosynthetic rate sufficient to promote carbohydrate accumulation. Green rabbitbrush was controlled about 80% with a single application of 2,4-D butyl ester at 3 lb/A after the new twigs were 3 inches long and while soil moisture contents were sufficient for active growth. Differences in susceptibility between the two species are compared with morphological, phenological, and physiological differences, and seasonal patterns of susceptibility are further compared with environmental conditions.

Radioactive sucrose-C14 and serine-C14 were “fed” to excised leaves from red kidney bean plants at various times following atrazine treatment. The distribution of C14 in the various labeled compounds was determined by two-dimensional paper chromatography and subsequent elution and counting. The results indicated that other processes entirely independent of the photosynthetic block are also involved in the herbicidal action. Atrazine did not affect the rate of respiration of excised embryos of red kidney bean plants.

Inulin or a closely related analog was the major available carbohydrate component of western ironweed (Vernonia baldwinii Torr.) roots. Fructose, glucose, sucrose and other gluco-fructosans made up the remaining carbohydrate fraction. Reductions in ironweed vigor as a result of annual mowing were caused by a decrease in dry weight of the root system rather than a permanent decrease in carbohydrate percentage. Use of carbohydrate percentage in predicting a physiological condition of ironweed was regarded as questionable. Carbohydrate content of roots was not necessarily related to stage of growth. Treatment of ironweed with 2,4-D did not permanently affect carbohydrate levels in the roots. Changes in root carbohydrate content after 2,4-D treatment were not considered decisive in killing ironweed.

The effects of rainfall and temperature upon herbicidal activity of 2-chloro-N,N-diallylacetamide (CDAA), 2-chloro-4,6-bis-(ethylamino)-s-triazine (simazine), and 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine), for the control of foxtail (Setaria spp.) were determined. CDAA spray was effective if applied to warm soil and if ½ inch of rain fell during the first week after application, unless a heavy rain fell immediately after application. The effectiveness of granules was not impaired by a heavy rain immediately after treatment or by a delay of 2 weeks before receiving ½ inch of rain. Simazine and atrazine sprays and granules were effective if 1 inch of rain fell within 15 days after application of simazine or if ½ to 1 inch fell within 15 to 20 days afterwards for atrazine. Mechanical incorporation aided in activation of simazine when rainfall was slightly below minimum required for activation.

The herbicide, N-(3-chloro-4-methylphenyl)-2-methylpentanamide was applied to the foliage of tomato, a tolerant species, and eggplant, a susceptible species. Both species increased in tolerance to the herbicide with age but tomato increased at a much faster rate. Selectivity did not appear to be a function of differential wetting of foliage. Photosynthesis was shown to be involved in the phytotoxic action of the herbicide and starvation is suggested as a possible mode of action. Carbohydrates increased the tolerance of tomato plants and the fixation of labeled carbon dioxide in eggplant leaves was prevented by the herbicide.

In field plantings, granular 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) were the most effective herbicides, but injured Spiraea media, S. trichocarpa, Syringa prestoniae and Physocarpus opulifolius. Diuron also injured newly planted evergreens. Granular 3-amino-2,5-dichlorobenzoic acid (amiben), isopropyl N-(3-chlorophenyl)carbamate (CIPC), 2-chloroallyl diethyldithiocarbamate (CDEC) and 4,6-dinitro-o-sec-butylphenol (DNBP) did not cause injury. Preplanting application of ethyl N,N-di-n-propylthiolcarbamate (EPTC) reduced the vigor of the deciduous shrubs. Chamaecyparis and Thuja species were tolerant to simazine under greenhouse conditions, while tolerance in Juniperus varied according to species.

Excavation at biweekly intervals for 20 weeks of nutsedge clones grown from single tubers indicated that no dormant tubers formed until 6 weeks after foliar emergence. Tuber chains or fully mature rhizomes were not observed until the tenth week or long tuber chains until the eighteenth week. Rhizome length and tuber-basal bulb number increased throughout the season. Development of clones varied.

Approximately 75% of the inhibitory effect of a foliar application of 4-chloro-2-butynyl N-(3-chlorophenyl)carbamate (barban) on wheat was eliminated by dusting the seed before planting with 4′-chloro-2-hydroxyiminoacetanilide at a rate of one ounce per bushel. Other highly effective antidotes were 2,4-dichloro-9-xanthenone and N-methyl-3,4-dichlorobenzene sulfonamide. Barban antidotes were found in those chemicals that produced formative effects on plants.

Red alder (Alnus rubra Bong.) was readily killed by growing season treatments with a 1 to 1 mixture of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in diesel oil. Except for 1-inch-diameter trees, it was resistant to dormant season treatments. Treatments applied during moderate rain were less effective than during rain-free periods.

Fish used in these tests were the Israeli strain of the common carp, Cyprinus carpio; the Nile tilapia, Tilapia nilotica; the Java tilapia, T. mossambica; and the Congo tilapia, T. melanopleura. Israeli carp and either Nile or Java tilapia in ponds containing only these species virtually eliminated aquatic weeds, but when stocked into established populations of largemouth bass and bluegill results were less encouraging.

The propylene glycol butyl ether ester of 2,4-D or the dimethylamine salt of 2,3,6-TBA in 25 gallons water per acre effectively controlled Colorado rubberweed (Hymenoxys richardsonii (Hook.) Cockerell) at the prebud stage. From 2 to 4 pounds acid equivalent per acre of an ester of 2,4-D were satisfactory, depending on the relative importance of cost and speed of kill.

A 7-foot V-plow was modified so herbicides could be sprayed beneath the soil surface in stubble mulch fallow operations. This permits the incorporation of volatile herbicides without destroying plant residues. Weed control is achieved by action of the 7-foot sweeps during the herbicide application and later by the incorporated herbicide.

A mobile, metal cabinet sprayer is described, in which an electrically-powered, chain-driven carriage with spray assembly travels back and forth over the pots or flats to be sprayed.

Fresh seed of Tamarix pentandra Pall. germinated at 36 to 132 F., freely at 66 to 110 F. Seed stored at the same relative humidity maintained viability best at low temperatures. Viability of seed stored at a low relative humidity continued high for 6 months over a wide range of temperature, but viability was reduced within 15 days by relative humidity of 90–95%.

In experimental work with perennial weeds it is often desirable to apply large gallonages of solution from a boom plot sprayer. Moreover, since tillage is frequently a counterpart of the control procedure the sprayer must be constructed to withstand rough usage on cloddy land. The sprayer illustrated in Figure 1 can deliver from 2 to 100 gallons of solution per acre in proper spray pattern through standard nozzles. Being light and strong, it can be pushed comparatively easily across uneven surfaces.

Overall weight of the sprayer is 150 pounds. Rate of travel is gauged by a speedometer indicating zero to 10 mph. Pressure is supplied by a quickly replaceable air pressure tank and the liquid is held in a 2-gallon pressure container. Dosage rate is determined by speed of travel and size of nozzle orifice tip. Because of the large capacity of the liquid flow system from tank to nozzle, loss of pressure is slight even when heavy gallonages of solution are applied. All parts of the system are of copper or brass except the solution tank which is of galvanized iron. However, since the outlet from tank to tubing is at the center of a dished bottom, drainage is good. Pet-cocks at each end of the boom permit thorough flushing. The boom can be set from a 6-inch to a 60-inch height and the angle of nozzle to the ground, adjusted over 20°. A supporting leg is provided at the rear of the frame to keep the sprayer upright when not in use. Air-pressure and speedometer gauges and the spray control valve are mounted directly in front of the operator. When applying 100 gallons of spray per acre, the 2-gallon solution tank permits coverage of 100 feet. Width of spray pattern is 8.5 feet.

In trials by three methods, witchweed (Striga asiatica) did not parasitize pineapple.

Seeds of witchweed (Striga asiatica) were found in undisturbed Lakeland sand in all layers to 60 inches deep.