Herbicide-treated Areas Research Articles

SHRUBBY CINQUEFOIL CONTROL CHANGES RANGE FORAGE PRODUCTION

Picloram, tebuthiuron, hexazinone, 2,4-D (isooctyl-ester), 2,4-D plus dichlorprop, and clopyralid were applied to native rangeland at two southern Alberta sites with heavy infestations of shrubby cinquefoil (Potentilla fruticosa L.). Yields of shrubby cinquefoil shoots, forbs, and grasses were measured in ungrazed areas for 4 yr after herbicide application. Hexazinone (grid-balls), 2,4-D, and 2,4-D plus dichlorprop reduced shrubby cinquefoil yields to almost zero. 2,4-D and 2,4-D plus dichlorprop increased grass yield and reduced forb yield compared with the untreated plots. Hexazinone initially decreased grass yield but, after 4 yr, grass yields were higher on the treated than on the untreated plots. Hexazinone and tebuthiuron treatments killed all vegetation within a 15-cm radius of the applied grid-balls and there was little recovery of the grasses on the tebuthiuron-treated areas 4 yr later. Picloram and tebuthiuron reduced shrub yields but many live shrubs remained after treatment. Clopyralid did not reduce shrub yields. In a further experiment, 2,4-D gave good shrubby cinquefoil control and grass yield increased. When this area was grazed the percent utilization of the total vegetation was similar for herbicide-treated and untreated areas but the amount of vegetation utilized increased by about 40% when the shrubs were controlled.Key words: Potentilla fruticosa L., picloram, tebuthiuron, hexazinone, 2,4-D, dichlorprop, clopyralid

Infiltration Rates and Sediment Production following Herbicide/Fire Brush Treatments

Termhtal infiltration rates were simiiar in soils on which a heavy whitebrush (Abysia lycioides) cover had been aerirny treated with 2 kg/ha (active ingredient) of 20% tebuthiuron pellets 4 years previously or on tebuthiuron-treated plots which had been prescribed burned the winter about 9 months prior to infiltration measurements, compared to untreated sites. However, sediment production was greater from plots treated with the herbicide than from areas subjected to the herbicide-fire system or from untreated plots. Only minor variations in infiltration rates occurred among sites originaiiy dominated by running mesquite (Prosopis reptuns) which were aerially sprayed with 2,4,5-T + picioram (1:l) at 1.1 kg/ha 3.5 years previously, burned 10 months previously, subjected to the herbicide-fire system or left untreated. However, sediment production on the running mesquite areas which had been sprayed tended to be greater than on untreated plots. Sediment production on areas subjected to the herbicide-prescribed burning system tended to be less than from brush-covered plots. Differences in sediment production In both experiments were generally attributed to siightly reduced mulch loads and mulch covers where the brush was removed as a leaf mulch donor by herbicide treatment. Prescribed burning apparently compensated for 10s~ of brush leaf mulch by promoting grass cover on herbicide-treated areas.

Differential Grazing Use of Herbicide-Treated Areas by Cattle

Differential Grazing Use of Herbicide-Treated Areas by Cattle

Effects of Positive and Negative Nitrogen Perturbations on an Old-field Ecosystem

The effects of contrasting nitrogen stresses on an old-field ecosystem were investigated. A positive stressor (urea fertilizer) and a negative stressor (AmitroleT herbicide) were each applied to four replicate 21.0 x 30.5 m plots on 25 July 1975. Four control plots were also established. Standing crop biomass (live), dead plant material (detritus), net primary productivity and species diversity (richness and apportionment) were used to evaluate ecosystem response to positive and negative stressor application. Standing crop biomass was significantly (p < 0.01) reduced in the herbicide-treated plots for approximately 3 months following treatment; standing crop biomass in ureatreated plots did not differ significantly from control plots following treatment. No significant differences in dead plant material were found between treatments and control plots at any time during the study. Fertilized plots exhibited peaks in seasonal primary productivity 2 weeks prior to control and herbicide-treated areas. Net primary productivity within positive or negative treated plots did not differ significantly from control means; however, positive and negative treatment plots differed significantly (p? < 0.05) from each other for approximately 6 weeks following treatment. Species richness (D = S 1/lnN) and evenness (e = H'/lnS) values increased dramatically in herbicidetreated plots as compared to either control or urea-treated plots. It appears that young ecosystems respond more to changes in community structure (e.g., species richness) than to changes in community function (e.g., primary productivity) following negative stress treatment; the reverse response appears true for young systems treated with a positive stressor.

FIELD CONFIRMATION OF AN INDEX FOR PREDICTING YIELD LOSS OF WHEAT AND BARLEY DUE TO WILD OAT COMPETITION

Indices of competition of 0.0339 for wild oats (Avena fatua L.) in wheat (Triticum aestivum L. emend Thel.) and 0.0230 for wild oats in barley (Hordeum vulgare L.) as developed by Dew (1972) were confirmed. Actual yield loss determinations were made by utilizing data collected from herbicide-treated (considered wild oat-free) and non-treated areas on field-scale trials scattered across Western Canada.

Karbutilate for Weed Control on Sagebrush Rangelands

Procedures were developed for simultaneous control of big sagebrush(Artemisia tridentataNutt.), green rabbitbrush [Chrysothamnus viscidiflorusVar.Viscidiflorus(Hook.) Nutt.] and downy brome(Bromus tectorumL.) with the herbicide karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxyphenyl)-1, 1-dimethylurea]. After a season of fallow, the herbicide-treated areas were seeded with perennial grasses. During the 4 yr of testing at several locations, karbutilate at 1.1 kg/ha controlled the shrubs and downy brome. A herbaceous fallow was maintained with 0.6 kg/ha of the herbicide, but 1.1 kg/ha was necessary for green rabbitbrush control. Perennial grass seedling establishment was highly variable among sites and years of testing. If germination of the seeded species occurred in the fall, stands were poor. When germination was delayed by the onset of cold weather until spring, excellent stands were obtained on plots treated 1 yr previous to seeding with 1.1 kg/ha of karbutilate. Residual herbicide activity was harmful at the time of fall seeding but herbicide residues declined by spring as shown by bioassay of soils.

GRAIN APHIDS IN NEW BRUNSWICK: III. APHID POPULATIONS IN HERBICIDE-TREATED OAT FIELDS

From similar initial populations, aphid infestations became higher in herbicide-treated areas of oats than in similar untreated areas. Fewer coccinellids were present in these treated areas. The inclusion of an aphicide with the herbicide applications held subsequent populations of aphids to the level of those in untreated plots. Although populations as high as 250 aphids per tiller occurred, no reduction in yields of grain or straw was found in 1962 or 1963.