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.

Field trials conducted in the three major peppermint-producing regions of Oregon showed that repeated applications of bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] at 2.2 kg/ha controlled Canada thistle [Cirsium arvense (L.) Scop.] in peppermint (Mentha piperita L.) selectively. Repeat applications of 2.2 kg/ha controlled Canada thistle better than single applications of 3.4, 4.5, or 6.7 kg/ha. Late May or June applications were more effective than early May applications. The number of Canada thistle shoots was reduced 82% 10 months after repeat applications but had almost returned to the original number 22 months after application. Basipetal translocation of bentazon was demonstrated by observing bentazon injury symptoms on untreated Canada thistle shoots which were attached by a root to bentazon-treated shoots.

A compact incorporator-planter, which incorporates herbicides into moist soil simultaneously with planting of cotton (Gossypium hirsutum L.), was constructed and evaluated over 3 yr using six herbicides. Weed control was consistent with that reported for large, cumbersome units utilizing standard planters and incorporating units from ground-driven rotary tillers and was enhanced in seasons in which rain fell during the first 3 weeks after planting. Among the dinitroaniline herbicides, dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) controlled barnyardgrass [Echinochloa crus-galli (L.) Beauv.], and redroot pigweed (Amaranthus retroflexus L.) most effectively. Cotton stands and yields were equivalent to those obtained using standard cotton-planting methods.

Perfluidone {1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl] methanesulfonamide} controlled wild Allium species when applied in the fall, winter, or early spring after the plants had emerged in bermudagrass [Cynodon dactylon (L.) Pers.] and zoysia (Zoysia spp.) turf. A single 3.4- or 4.5-kg/ha rate generally resulted in good to excellent control, but repeated treatments for 2 consecutive yr were required to obtain consistent control.

Weed control trials were conducted on loblolly pine (Pinus taeda L.) or slash pine (Pinus elliottii Engelm.) seedbeds at 12 locations in the southeastern United States. Good weed control was obtained from 2,4-bis-(isopropylamino)-6-(methylthio)-s-triazine (prometryne) at 2.2 and 4.5 kg/ha; N,N-dimethyl-2,2-diphenylacetamide (diphenamid) at 4.5 and 9 kg/ha; α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) at 1.1 and 2.2 kg/ha; and 2-ethylthio-4,6-bis-isopropylamino-s-triazine (GS-16068) at 2.2 and 4.5 kg/ha as preemergence applications immediately followed by irrigation. Diphenamid and trifluralin treatments were not injurious to either pine species at either rate. GS-16068 was only slightly injurious at the high rate at one location. Prometryne was injurious at two locations at the high rate and at one location at the low rate.

The fast growing woody plant known as marabú, (Dichrostachys nutans), is native to Africa but it has found a favorable environment in Cuba. At present, dense stands of it, 20 feet and more in height, cover vast areas of the island, and a great deal of land has had to be abandoned on account of it. The ease with which it becomes established in turf or in neglected sugar cane lends exceptional interest to the development of methods of controlling, or, if possible of eradicating the plant.

An 1130 IBM computer was used to process data from experimental plots to evaluate performance of preemergence herbicides in Hawaiian sugarcane fields (planted with varieties of four Saccharum spp.). The evaluation technique compares performance of experimental herbicides with the performance of three standard herbicides [2-(ethyl-amino)-4-(isopropylamino)-6-(methylthio)-s-triazine (ametryne), 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron)] under a wide range of environmental conditions. Under most conditions the substituted triazine 2-(sec-butylamino)-4-(ethylamino)-6-methoxy-s-triazine (GS-14254) gave better total weed control without crop toxicity than any of the three standards, and was particularly well-suited to regions of high rainfall.

British Agriculture has existed for at least a thousand years, and it would require a book to record the major developments in weed control. My concern today is with the events of the past 25 years during which weed control has become established as a science, and herbicides have been given a widespread introduction. I hope to set these events against a historical background as they relate to Great Britain, and thereafter, to draw out some thoughts on the impact that modern weed science is making and will make in the future on crop production and land use.

Napropamide [2-(a-naphthoxy) N,N-diethylpropionamide] applied to cranberry (Vaccinium macrocarpon Ait.) as a granular or wettable powder formulation at 20 kg/ha in March 1978 controlled aster (Aster subspicatus Nees) and birdsfoot trefoil (Lotus corniculatus L.) without any phytotoxicity to ‘McFarlin’ cranberry vines. Earlier application in February was ineffective, and late application in April injured the vines. Napropamide 10% granular applied at 14 kg/ha in March 1979 controlled aster 90% and birdsfoot trefoil 70%, and the 50% wettable powder formulation controlled aster 90% and birdsfoot trefoil 80%. Applications of granular napropamide at 12 kg/ha in March of 1979 or 1980 controlled both weeds 70%.

Primary root cells from five dinitroaniline-resistant (R) and three susceptible (S) goosegrass biotypes from North Carolina and South Carolina were observed by transmission electron microscopy to determine whether resistance was associated with changes in cell wall formation. Cell wall malformations were found in some cells from two of the R-biotypes and in one of the S-biotypes. Malformations consisted of partially deposited cell walls and the inclusion of cell wall material in the cytoplasm. Some of the affected cells also had abnormal, lobed nuclei and malformed mitochondria. There seems to be little or no correlation between dinitroaniline resistance and cell wall malformations.

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.

Field trials were conducted from 1991 to 1993 in the northern cotton-producing area of Alabama to evaluate the interaction of various production inputs for pest management and cotton development, maturity, and yield. Two levels of tillage (conventional and no-till), herbicide (1.12 and 2.24 kg ai ha−1 fluometuron, preemergence, with post-directed herbicides), insecticide (0.5 and 0.85 kg ai ha−1 aldicarb, in-furrow), and fungicide (0.9 kg ai ha−1 quintozene plus ethridazole, in-furrow or 0.14 kg ai ha−1 metalaxyl, hopper-box) programs were evaluated. The inputs investigated did not interact significantly to change the overall production strategy. Prickly sida required a higher level of herbicide input than did the entireleaf/ivyleaf morningglory complex. Both species were sufficiently controlled using reduced levels of fluometuron without sacrificing yield; however, cultivation was necessary in conventional tillage treatments to maintain control. A postemergence-directed herbicide treatment was also necessary for weed control, regardless of tillage. Decreasing the levels of each input simultaneously did not interact to affect cotton stand, height, early-season thrips counts, cotton maturity, or yield. Cotton was shorter in no-till than conventional plots.

The control of roadside weeds and brush has always been a major problem of roadside construction and maintenance engineers. People charged with the responsibility of keeping our highways, county, trunk and local roads free of weeds and brush have heretofore found the control of unsightly weeds and brush a major and laborious problem and expense. For the control of many annuals such as hemp, giant ragweed, small ragweed, daisy fleabane, etc., a very thorough, systematic mowing program, coupled with the establishment of a heavy grass cover has in many instances sufficed to keep weed growth down to a minimum. However, for the control of such roadside weeds as Canada thistle, perennial sow thistle, poison ivy, etc., as well as for the control of all types of brushy growth, the mere mowing and laborious cutting of such plants has not resulted in eradication. The mowing of perennial weeds and brush is like “picking apples off a tree” — such picking does not kill the tree. Furthermore, programs of control involving brush have had to be repeated every two or three years at terrific expense to the tax payer. Laborious mowing and hand cutting is followed quickly by regrowth, which in a year or so is as bad or worse as the original stand which was removed.

The absorption and distribution of 14C terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine] and 14C-fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] in cotton (Gossypium hirsutum L. ‘SJ-1’) and snapbean (Phaseolus vulgaris L. ‘Tenderette’) seeds during germination was studied. Seeds of the susceptible snapbean absorbed larger amounts of both herbicides from soil than the resistant cotton seeds. The herbicides accumulated mainly in the seed coat of cotton which shed following emergence, with no translocation to the seedling leaves. In snapbean seeds the herbicides accumulated in the cotyledons, which served as a source for acropetal flow to the developing foliage of the young seedling.

Three field experiments, each for a 2-yr duration, were initiated to evaluate the efficacy of TCA (trichloroacetic acid) and dalapon (2,2 - dichloropropionic acid), alone or in combination, for the selective control of alsike clover (Trifolium hybridum L.) and red clover (T. pratense L.) during the establishment of birdsfoot trefoil (Lotus corniculatus L.). TCA at 6.7 kg/ha gave 95% control of alsike control. TCA at 13.5 kg/ha gave 92% control of red clover and the combination treatment of 6.7 kg/ha of TCA plus 9.0 kg/ha of dalapon gave 95% control of red clover. Birdsfoot trefoil tolerated TCA and dalapon alone or in combination.

Sainfoin (Onobrychis viciaefolia Scop. ‘Melrose’) seedlings tolerated at 15:1 commercial formulation of the sodium salts of MCPB {4-[(4-chloro-o-tolyl)oxy] butyric acid} and MCPA {[(4-chloro-o-tolyl)oxy] acetic acid} applied at rates up to 2.2 kg/ha in the greenhouse and 3.4 kg/ha in the field. Broadleaf weed control was only fair. Applications of 1.1 kg/ha, 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] ester caused moderate damage to sainfoin initially, but no reduction in yield. Weed control was fair to good. Higher rates of 2,4-DB caused excessive injury unless a heavy growth of weeds protected the sainfoin from contact with the spray. The use of 2,4-D [(2,4-dichlorophenoxy) acetic acid] amine damaged sainfoin severely, although weed control was fair. Nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) at 3.4 kg/ha caused spotting on sainfoin leaves with no reduction in growth. Initial weed control was good, but sainfoin seedlings did not suppress new weed growth. Herbicide applications made when sainfoin had 1 to 3 leaves provided the best combination of crop tolerance and weed control.

Castorbeans (Ricinus communis L.) are extremely tolerant of the rotary hoe. Its timely use plus cultivation gave effective weed control in castorbeans. The preemergence herbicides, used either alone or in combination, that appeared most promising for selective control of weeds in castorbeans were: 2-chloro-N,N-diallylacetamide (CDAA), dimethyl-2,3,5,6-tetrachloroterephthalic acid (DCPA), ethyl N,N-dipropylthiolcarbamate (EPTC), N-1-naphthylphthalamic acid (NPA), 2,6-dinitro-N,N-dipropyl-alpha, alpha, alpha-trifluoro-p-toluidine (trifluralin), and propyl dipropylthiolcarbamate (R-1607). The most dependable weed control practice in castorbeans was the use of preemergence herbicides in combination with rotary hoeings plus cultivation.

Plants of curly dock (Rumex crispus L.) were subjected to soil temperatures of 10, 15, 26, and 35 C in a growth chamber. A soil temperature of 10 C was most favorable for root growth and production of large seeds. The highest yields of seeds and fruit were obtained at 26 C. Significant reductions in seed and fruit production, wt per 100 seeds, plant height, and growth rate occurred at 35 C. The total germination of mature seeds was not affected by soil temperature, but the seeds ripened at 26 and 35 C germinated faster than those from the 10 and 15 C treatments.