Weed spectrum

Glufosinate has a broad weed spectrum (little to no selectivity), and is therefore sometimes marketed along with genetically engineered glufosinate-resistant crops (cotton, canola, maize, and rice). While this raises some concern in some parts of the world, transgenic technology has been widely accepted in the western hemisphere. Nevertheless, neither... 

Today s herbicides can be applied in a variety of different ways to the crop. They can be applied as single component products or as combination products, using the different properties and weed spectrum of the components of the mixtures. 

While several of these organic chemicals reached a commercial stage, all had major limitations. Among those limitations were marginal crop selectivity, limited weed spectrum, too short duration of activity, serious failures on some soils or under certain weather conditions, offensive smell or touch, corrosion of spray equipment, drift, secondary adverse effects, etc. At best, many of these organic chemicals had to be used at high rates (e.g., 4-101b/A or 4.5-11.2kg/ha), and were often too costly for their limited benefit. 

Registrations have been granted for several new herbicides that are being introduced into sugarcane their use is still relatively small. These are briefly described as to application method, rate, and weed spectrum. 

Producers attempt to eliminate perennial weeds in small fruits with soil fumigation and plastic mulches. In caneberry, low rates of simazine can be used in heavier soils. Caneberry has good crop tolerance to other preemergence herbicides such as oryzalin, napropamide, and pendimethalin, though their weed spectrum may be reduced compared to simazine. 

Linuron, a substituted urea introduced by Hoechst in 1960, is employed primarily as a preemergence herbicide but it also has contact effect on foliage (Fig. 3). Linuron is used principally in soybeans, corn, sorghum, wheat, and potatoes. It is often mixed with other herbicides to broaden the weed spectrum. 

In practice, herbicide selection is limited by the number of different products available for use in a particular crop, the weed spectrum, the possible rotational consequences of using residual products, and the treatment cost. In some crop rotations choosing a herbicide from a different mode-of-action group each year may be a viable option, whereas in others the choice of registered products may be limited, and the farmer may have to rely on similar products more frequently. Again, short-term consideration of the important... 

Chapter 5, entitled Safeners for Herbicides , demonstrates the progress in this research field, bringing out new compounds that create highly competitive products for the farmers out of only partly selective herbicides having a very broad weed spectrum and very low application rates ( the chemical answer to genetically modified herbicide resistant crops ). 

This chapter aims to give an insight into the discovery of the triketone class of herbicides and their continuing development. A very qualitative picture of structure-activity relationships will be discussed and currently commercialized triketones, in terms of their use, weed spectrum, crop selectivity, environmental and toxicological profiles, and manufacture will be described. This chapter also contains an overview of the major companies activities in the field in the last two decades, focusing on compounds that are likely to be brought to the market, or were putatively close to development. 

The results presented here show that introduction of hetero atoms into the sidechain of the benzamide herbicides leads to biologically active compounds. The most active of these heteroalkyl analogs, 4b, possesses a similar weed spectrum and rate of use as for EL-107. In no case, however, did any of the analogs show activity superior to EL-107. 

In order to make sure the weed spectrum of cyclic phosphonates IVC-IVE, seven cyclic phosphonates were chosen to test at 150 and 75 g ai/ha for postemergence herbicidal activity against twenty-one species of dicotyledonous plants including fourteen species of weeds and seven species of crops. 

Table 5.25 Weed Spectrum of some cyclic phosphonates IVC-IVE... 

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