Several ring-substituted derivatives of benzoic acid inhibited pantothenate biosynthesis in Escherichia coli. The metabolic site of inhibition was the conversion of ketopantoate to pantoate. This action caused pantothenate-reversible reductions in growth only in strains of E. coli with inherent limited capacities for biosynthesis of ketopantoate. Inhibition of pantothenate biosynthesis was tentatively concluded to be of little physiological significance as a site of action responsible for herbicidal activities of benzoic acids.

Mature yellow foxtail [Setaria glauca (L.) Beauv.] infestations, growing in rows of corn, were harvested in 3 foot segments from paired 30 foot rows of corn. Basic analyses of variance were calculated so that the variances of plot sizes involving multiples of 3 feet could be determined and compared. Precision indices were calculated for harvesting various fractions of the plot area. Loss of precision did not exceed 25 percent when only 40 percent of the total area was harvested in random samples of 1-row X 3 feet, or in multiples of this basic unit. Practical implications of the findings are related to estimates of weed yields in crop-weed ecology studies and herbicide evaluation tests.

Among 15 different herbicides tested for eradication of Turkey oak (Quercus laevis Walt.) over a period of four years on Lakeland fine sand in Florida, only monuron, diuron, and fenuron at minimal rates of 10 lb/A were effective. One full growing season after application was required for complete kill. Phenoxy compounds gave variable top-kill but not satisfactory control. AMS, dalapon, and four formulations of benzoic acid were ineffective in these tests.

Out of 13 different grasses, Pensacola bahiagrass (Paspalum notatum Flugge) and weeping lovegrass (Eragrostis curvula Schrad.) were best adapted to these deep sandy soils. Seedbed preparation was essential to obtain a good stand of either. After establishment, the lovegrass vigorously persisted throughout the experiment; the bahia also persisted but the lack of fertilization was extremely evident. Both grasses could be established satisfactorily on soil treated two years earlier with monuron or diuron at 10 lb/A.

Absinth wormwood (Artemisia absinthium L.), a perennial, native to Europe, has become abundant during the last decade in several locations in western Canada. Reports received during the Saskatchewan Weed Survey suggest that at least some of the introductions into this area were by immigrants from Europe, who believe it to have medicinal properties. Silver-grey in color and covered with fine hairs, the herbaceous stem grows to a height of 2 to 4 ft, often branching profusely. The leaves are up to 5 in. long and are two to three times divided into lanceolate segments. Numerous, drooping heads, about 3/16 in. in diameter, develop in leafy panicles. Yellow or purple florets are borne on a hairy base. The whole plant has a strong, penetrating odor, common in other species of this genus. In Europe it is used as a stimulant (tea and liquor).

The herbicide 2,4-D is commonly used for sucker control in hazelnut (Corylus avellana L.). However, the use of 2,4-D for sucker control has been implicated in delaying natural abscission in hazelnut. Hazelnuts naturally abscise and are collected from the orchard floor. Delays in abscission may reduce nut quality due to the onset of the rainy season, increasing mold and mud in the nuts. The effect of basal-directed applications of 2,4-D on hazelnut abscission, yield, and quality was assessed. In the first study, four basal-directed applications of 2,4-D (1.06 kg ae ha−1) did not affect hazelnut abscission, yield, or quality compared with glufosinate (1.1 kg ai ha−1) or manual pruning. In a second 3-yr study, a single yearly simulated drift of 2,4-D to the tree canopy at 0.06 and 0.6 mg L−1 increased the growing degree-day requirement from 50 to 141 to reach 50% hazelnut abscission, compared with the nontreated control. This is the equivalent of 5 to 15 calendar days. No effect was observed in the third year of the study when the simulated drift was not performed. No differences in abscission were observed with basal-directed applications of 2,4-D at rates up to 4.4 kg ha−1 when applied four times each season during all 3 yr of the study. Simulated drift reduced hazelnut yield by up to 37% and reduced the percentage of marketable nuts during 1 yr of the study. No effect on average kernel weight was observed. However, 2,4-D drift did delay hazelnut abscission, highlighting the importance of drift control measures.

Field studies have shown primisulfuron to be more injurious to sugarbeet than nicosulfuron 1 and 2 yr after herbicide application. Experiments were initiated to determine if primisulfuron is more injurious to sugarbeet grown in a nutrient culture and if the difference in sugarbeet response is a result of greater uptake, translocation, or acetolactate synthase (ALS) site sensitivity with primisulfuron. Concentrations of primisulfuron and nicosulfuron that reduced sugarbeet growth by 50% were 1.9 and 8.9 μg ai L−1, respectively, at pH 6.5. The pH of the nutrient solution did not influence sugarbeet response to either herbicide. Uptake of primisulfuron was greater (3%) than that of nicosulfuron (1%). Translocation (expressed as a percent of uptake) of nicosulfuron was more rapid than primisulfuron. Fifty-seven percent of the absorbed nicosulfuron translocated out of the root during the 12-h pulse period, while an equal concentration of primisulfuron was not translocated out of the root until 48 h after pulsing. The total nicosulfuron translocated after 144 h was half that of primisulfuron. The nutrient solution taken up by sugarbeet in the 12-h pulse period was reduced by 41% in the presence of either herbicide compared to the untreated control. The ALS enzyme was a minimum of 15 times more sensitive to primisulfuron compared to nicosulfuron which may account for greater sugarbeet response to primisulfuron.

Stands of Russian knapweed (Centaurea repens L.) were reduced over 80 per cent by several combinations of crops, cultivation and herbicides. Two of the best crop rotations in a 4-year trial were: (1) a short season of intensive cultivation and a mid-August seeding of bromegrass that was sprayed with 1 lb/A of butoxyethanol ester of 2,4-dichlorophenoxyacetic acid (2,4-D) during June and 1 or 1½ lb/A during August of the second and third years. (2) Bromegrass seeded with an oat companion crop sprayed with ⅓ lb/A of 2,4-D ester the first year and annual applications of 2,4-D in June and mid-August during the second and third years. The best use of non-selective herbicides in two 2-year trials was spring application of 4 lb/A of diethylamine salt of 2,3,6-trichlorobenzoic acid (2,3,6-TBA) or 6 lb/A of diethylamine salt of polychlorobenzoic acid (PBA), plowing 10 days later, and a corn crop sprayed with ⅓ lb/A of 2,4-D ester followed by a spring-seeded oat crop sprayed with d13 lb/A of 2,4-D ester and postharvest application of 4 to 6 lb/A of 2,3,6-TBA and 6 to 8 lb/A of PBA, and plowing 10 days later. Reinfestation from established plants was not prevented, but annual application of 2,4-D prevented reinfestation from seedlings.

Growth of Oxalis cernua Thunb. was determined in different temperature regimes. Growth occurred in the 55 to 75 F range. Temperature variation promoted growth. Bulbs sprouted more rapidly and uniformly after storage at 35 F than after storage at 95 F. The weed probably is best adapted to areas with winter soil temperatures between 55 and 75 F.

As a representative of the chemical industry, this subject is a rather difficult one to discuss. When one stops a moment to think about the role of the university in herbicidal testing, immediately he realizes that this probably never has been defined and it appears for the most part the administration and research personnel of each university follow the road that is the best of their liking. Far too often, they do not stop and ask themselves whether they really are taking the proper route.

In discussing this topic, one can take the approach that all universities, and some are in this category, are doing an excellent job and compliment everyone that an adequate job is being done. Or one can conclude that the universities should not be doing field evaluations (and please understand this is in the minds of a few university administrators) or the answers to the field problems can be solved in the laboratories; or finally, one can conclude that the universities are not doing a proper job and that considerable improvement must take place. Perhaps I will make some new enemies today (although the Chairman, Dr. Ries, indicated I could take any approach I preferred), but I am of the opinion that our university and experiment station system primarily is not doing a proper job in testing herbicides and that they must take a more active role in the future than they have in the past.

According to Bonner, at least three different oxidase systems may be involved in the final step of the transfer of electrons to oxygen. Each of the terminal oxidases has been shown to occur in many plants and in many relative combinations.

A 4.6-m-long, segmented, flexible-pipe ropewick applicator was constructed to apply picloram (4-amino-3,5,6-trichloropicolinic acid) to leafy spurge (Euphorbia esula L. ♯ EPHES) and other weed species. Gauge wheels on each ropewick applicator segment permit height adjustments, and a loose, independent, vertical flexing action permits the segments to effectively traverse depressed or raised areas. The applicator was designed for use in pastures with rough, uneven terrain where it is difficult to uniformly wipe herbicide solution on plants with a rigid-pipe ropewick. The applicator was found to be durable and effective in applying picloram to leafy spurge.

Harvest weed seed control (HWSC) is an effective technique for managing wild radish (Raphanus raphanistrum L.), a weed that retains its seed until harvest. However, earlier flowering time (leading to increased seed shedding before harvest) is a risk to HWSC effectiveness. This study investigated the effects of repeated HWSC on the evolution of R. raphanistrum flowering dates, using two methods: an adaptation of the SOMER model that included flowering genes (called SOMEF); and a mathematical calculation of the endpoints of flowering date evolution utilizing the relevant life-history equations. In weed management systems with highly effective herbicides, the additional use of HWSC predicted R. raphanistrum population extinction. Low weed numbers and rapid extinction meant that any gradual evolution in days to first flower (DFF) was insufficient to lead to HWSC evasion. In alternative management systems with less vigorous herbicide control and using HWSC, modeling predicted a maximum 2- to 3-d reduction in DFF. In contrast, mathematical calculations of the phenotypes maximizing seeds returned to the seedbank predicted an endpoint to evolution of 12-d earlier flowering, which matched field observations. However, genetic change postulated by the mathematical calculations was not hampered by a restriction to changing DFF allele frequencies. Unknown accompanying genetic changes could affect germination dates or flowering triggers.

Simulation modeling that included only flowering genes failed to predict the magnitude of an observed 12-d reduction in DFF. Differences between the 12 d observed in the field (and predicted using mathematical calculations) and the modest changes demonstrated in this field-based modeling study are postulated to be due to unaccounted evolutionary changes in R. raphanistrum.

This paper is a review of and a commentary on the published addresses of WSSA presidents from the founding of the Society through 2000. The paper's assumptions are that the presidential remarks will reveal what the Society has emphasized, what its major concerns and goals have been, and how the presidents have addressed what they considered to be important issues. Seven issues have been addressed by many presidents. These include the importance of agricultural production and profit, the necessity of herbicides, weed science and the environment, the regulation of herbicides, the need for education, comparison of weed science and other plant protection disciplines, and the problem of herbicide resistance.

The possible use of the phenoxybutyric acids as selective herbicides in the pea crop has been recognized from the beginning of their development (3) and preliminary experiments with the more important compounds of this series carried out in 1954 indicated that 4–(2–methyl–4–chlorophenoxy)butyric acid [4–(MCPB) showed the most promise (1). To date no results have been reported on the persistence of MCPB in peas; experiments were, therefore, undertaken to determine this under field conditions.

The most economical time to control invading noxious shrubs is at an early stage in the invasion, when stands are sparse. One method of doing this is with a ground spray rig (Fig. 1). With such a rig the problem is to get the guns out from the vehicle so that a reasonable-sized swath can be covered. The out-rigger apparatus described herein can be used to cover a swath of 50 feet where the brush is fairly dense, to 90 feet on sparser stands.

Weeds have plagued man in his agricultural pursuits since biblical times in spite of backbreaking efforts to control them by hand and mechanical methods. At this second meeting of the Weeds Journal of Weed Society of America it appears appropriate to review briefly some of the modern accomplishments in weed control and to take stock of future needs.