Investigations were conducted to determine the effects of the herbicide glyphosate and its time of application on the control of johnsongrass. Johnsongrass plots were divided into areas designated undisturbed, spring plowed, and clipped. These areas were compared to determine differences in control of johnsongrass when using glyphosate with different management procedures. Glyphosate was applied at weekly intervals and treatment effects were statistically analyzed. There were three replications of each treatment. It appears from the results that: Glyphosate kills approximately 100% of the johnsongrass topgrowth regardless of the application date. Height of the johnsongrass plant at the time of glyphosate application had little influence on the ability of the herbicide to kill the rhizomes. Rhizomes from plants that had received an application of glyphosate produced a significantly lower number of plants than did rhizomes from untreated plants. The management procedures (spring plowed, clipped, undisturbed) had no effect on the ability of glyphosate to kill the rhizomes. As glyphosate applications were applied later in the growing season, johnsongrass control increased. In 1975 glyphosate utilized with spring plowing produced better total johnsongrass control than either clipped or undisturbed plots which had utilized glyphosate. In 1976 there was no significant difference in the control given by the three methods.

Alachlor [2'-chloro-2',6'-diethyl-N-(methoxymethyl) acetanilide] in combination with linuron [3-(3,4-dichlorphenyl)-1 methoxy-1-methylurea (n'-(3,4-dichlorophenyl)-N-methoxy-Nmehtylures)] and metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one 4-amino-6-(1,1-dimethy-ethyl)-3-(methylthio)-1,2,3-triazin-5(4 H)-one] was evaluated for its control of broadleaf and annual grasses in Mitchell soybeans (Glycine max L.) under four different tillage conditions. The experiment was conducted in the summers of 1978 and 1979. The tillage treatments evaluated were conventional tillage, double disking, single disking, and no-tillage. Alachlor at 2.2, 2.8, and 3.4 kg/ha was used alone and in combination with metribuzin at 0.4, 0.6, and 0.8 kg/ha and linuron at 0.6, 0.8, and 1.2 kg/ha. All treatments were compared with a check which received no residual herbicide application. All plots received an application of glyphosate [N,N-bis(phosphonmethyl) glycine] at 2.2 kg/ha to control emerged vegetation. The results of the experiment showed no interaction between tillage conditions and herbicide applications. There were no significant differences in broadleaf weed control or yields in the tillage plots for either 1978 or 1979. Significant differences were found in yields as affected by herbicide treatments in 1978, but none were found in 1979. Differences did not follow any logical pattern and were not consistent between years.

No description available.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

There is little information published on red sorrel (Rumex acetosella L.), a perennial weed that is considered a serious problem in wild blueberry production. Hexazinone, a photosystem II inhibitor, has been used in wild blueberry fields for more than 30 years. Hexazinone efficacy on red sorrel has declined over time. Therefore, a two year study was conducted to examine hexazinone alternatives that can be sprayed in wild blueberry fields. Red sorrel ramets from mature blueberry fields were tested to determine whether long-term spraying of hexazinone selected for resistant red sorrel. The results show that hexazinone+rimsulfuron/nicosulfuron may be a alternative for hexazinone. Red sorrel from some blueberry fields is hexazinone-resistant and the resistance is caused by a Phe255 to Val mutation in the psbA gene.

No description available.

Cirsium arvense (L.) Scop. (Canada thistle) is a persistent perennial pasture weed in Eastern Canada. Single control measures such as cultural, chemical, and biological methods are not effective in long term reduction of the weed population. The objectives of this research project were to evaluate the efficacy of various traditional control methods and to attempt to integrate them. / The effectiveness of Urophora cardui L. as a biological control agent is limited due to a lack of synchrony between the agent and the weed. This can be improved through integration with herbicides or mowing in time or space. Other biological control agents such as Orellia ruficauda Fab., Cassida rubiginosa Muell., and Puccinia punctiformis (Str.) Rhol. resulted in limited suppression of the weed population. Mowing was not effective in sustaining weed reductions for longer than one year. Application of clopyralid or 2,4-D/dicamba effectively reduced the weed population. The application of 3.37 kg a.i. ha$ sp{-1}$ 2,4-D/dicamba or 0.3 kg a.i. ha$ sp{-1}$ clopyralid with the spring and summer mowings were the most effective mowing/herbicide combinations over the two-year period.

No description available.

Two field studies examining direct ecological weed control practices were conducted in Lexington, Kentucky. The first evaluated weed control efficacy and influence on yields of several mulches in two organically-managed bell pepper (Capsicum annum) production systems for two years. Peppers were planted in double rows in flat, bare ground or on black polyethylene-covered raised beds with drip irrigation, and four mulches (straw, compost, wood chips, and undersown white dutch clover (Trifolium repens L.) living mulch) were applied to the two production systems. In both years, polyethylene-covered raised beds produced higher yields than the flat, bare ground system. In the second year, the polyethylene-covered bed system coupled with mulching in-between beds with compost or wood chips after cultivation provided excellent weed control and yields. The second field study evaluated the efficacy of soil solarization and shallow cultivation on the invasive and noxious weed johnsongrass over two years (Sorghum halapense). A soil solarization treatment, using clear plastic stretched over soil for eight weeks, and a cultivated bare fallow treatment, utilizing a tractor pulled cultivator implement equipped with sweep blades, were randomly applied during the summers of 2003 and 2004 to a field infested with johnsongrass. Solarized and cultivated plots in both years were lightly tilled 8 months after completion of the initial treatment period. At the conclusion of the experiment the johnsongrass population was significantly reduced in all treatments and in the control plots compared to the original infestation. These two experiments testing direct weed control practices (mulching, cultivation, solarization) were undertaken in the context of an ecological weed management plan that includes long term strategies to reduce weed infestations such as crop rotation, cover cropping, and fertility management that are essential for organic farmers.

In recent years global concern over the development of herbicide resistant (HR) weeds has lead to interest in integrated weed management (IWM) strategies. IWM seeks to relieve selection pressure for herbicide resistance by utilizing mechanical and cultural controls in addition to herbicides. The situation experienced by Saskatchewan lentil growers with large populations of group 2 herbicide resistant wild mustard provides an ideal model system to test our hypothesis that IWM strategies can provide robust weed management and maintain crop yields. The first study evaluated an IWM method targeting HR wild mustard in lentil. This study was conducted for 3 years between 2011 and 2013 at 2 locations at Saskatoon and Scott, Saskatchewan. It was a randomized two way factorial with weed control method and seeding rate as the main effects. Weed control treatments tested consisted of a control treated with a glyphosate burnoff, saflufenacil (Heat ™) herbicide, rotary hoeing, half rate metribuzin (Sencor ™) herbicide, a fully integrated treatment, and a full herbicide treatment. Three seeding rates representing 1, 2, and 4 times the recommended seeding rate were tested. The integrated treatment relied on increased seeding rate to reduce mustard biomass and produce yield, and at the highest seeding rate it was able to provide equivalent yield to the full herbicide system. The results of this study show that an integrated system utilizing an increased seeding rate can control resistant weeds and maintain yields to a similar level as a strategy that relies only on herbicides for weed control. The cultural practice of increasing crop seeding rate has been identified as having potential to provide non-chemical weed control and enhance the effects of herbicide application. The objective of the second study was to examine the interaction between increasing seeding rate and the dose response relationship of weeds to herbicide application. The experiment was a factorial design with four levels of lentil seeding rate and seven levels of fluthiacet-methyl herbicide application rate. The study was conducted at two locations near Saskatoon, Sk. in 2012 and 2013. Results of the experiment show that increasing lentil seeding rate decreased the total mustard biomass when herbicides were not applied or were applied at low rates. In addition increasing lentil seeding rate lowered the herbicide dose required to result in a 50% reduction in mustard biomass in 2012, though it had little effect in 2013. These results suggest that the practice of increasing seeding rate can work with herbicide application to reliably and effectively control weeds, even in situations where herbicides alone may not achieve good control.