Herbicidal spectrum

The pyridazinotriazines 214, prepared from 213, showed [84JAP(K)59116201 87MI1] a broad herbicidal spectrum against several... 

Its held of application is similar to that of 2,4-D. It is used as a postemergence foliage herbicide in cereals, flax and on pasture land at a rate of280 g-2.25 kg active ingredient/ha. It is effective mainly for the control of dicotyledonous weeds, killing both annual and perennial weeds. Its herbicidal spectrum differs somewhat from that of 2,4-D. Cereals are more resistant to MCPA than to 2,4-D, while the reverse is true for maize. 

This compound has a rather similar herbicidal spectrum to that of asulam, the main difference being that it is better tolerated by dicotyledonous crops (alfalfa, peas, potatoes). 

Before the discovery of streptomycin, pyrazinamide (126) was one of the front runners in the treatment of tuberculosis. A broad spectrum of biological activity has been associated with pyrazine derivatives, ranging from the herbicidal activity of (127) to antibiotic activity... 

A broad-spectrum grass and broadleaf corn herbicide Regulated metabolites in groundwater include the parent, isoxaflutole (RPA 201772), and its metabolites RPA 202248 [2-cyclopropylcarbonyl-3-(2-methylsulfonyl-4-trifluoromethylphenyl)-3-oxopropanenitrile] and RPA 203328 (2-methanesulfonyl-4-trifluoromethylbenzoic acid)... 

Pyraflufen-ethyl was primarily developed as a cereal herbicide to control a broad spectrum of broadleaf weeds. Pyraflufen-ethyl applied in early postemergence at 12 g a.i. ha provides excellent control of some important weeds such as Anthemis arvensis, Lamium purpureum and Sinapis arvensis and good suppression of Matricaria chamomilla, Stel-iaria media, Veronica persica and Viola spp. 

Sulfentrazone is a broad-spectrum, pre-emergent herbicide that provides good control over broadleaf weeds, grasses and sedges in crops and turf. The metabolism of sulfentrazone in animals and plants is similar. The major plant metabolite of sulfentrazone is 3-hydroxymethyl sulfentrazone (HMS). The soybean tolerance of 0.05 mg kg includes residues of sulfentrazone plus its major metabolite, HMS. The rotational crop tolerance includes residues of sulfentrazone and its major metabolites, HMS and... 

Precursors of phenylpropanoids are synthesized from two basic pathways the shikimic acid pathway and the malonic pathway (see Fig. 3.1). The shikimic acid pathway produces most plant phenolics, whereas the malonic pathway, which is an important source of phenolics in fungi and bacteria, is less significant in higher plants. The shikimate pathway converts simple carbohydrate precursors into the amino acids phenylalanine and tyrosine. The synthesis of an intermediate in this pathway, shikimic acid, is blocked by the broad-spectrum herbicide glyphosate (i.e., Roundup). Because animals do not possess this synthetic pathway, they have no way to synthesize the three aromatic amino acids (i.e., phenylalanine, tyrosine, and tryptophan), which are therefore essential nutrients in animal diets. 

Paraquat is a broad-spectrum contact weed killer and herbage desiccant that is used widely in agriculture and horticulture. Paraquat was originally formulated in 1882, but its herbicidal properties were not discovered until 1955. Since its introduction in the early 1960s, paraquat has been used extensively in about 130 countries, including the United Kingdom, Canada, and the United States, on a wide variety of agricultural crops (Fletcher 1974 Haley 1979 Kelly et al. 1979 Anonymous 1988). 

Paraquat (l,r-dimethyl-4,4 -bipyridinium) and its dichloride salt (1,1 -dimethyl-4,4 -bipy-ridinium dichloride) are broad-spectrum contact plant killers and herbage desiccants that were introduced commercially during the past 35 years. Today, they rank among the most widely used herbicides globally and are frequently used in combination with other herbicides. The recommended field application rates for terrestrial weed control usually range between 0.28 and 1.12 kg paraquat/ha (0.25 and 1.0 pounds/acre) for aquatic weed control, it is 0.1 to 2.0 mg/L. Target plant species are unable to metabolize paraquat and tend to contain elevated residues paraquat-resistant... 

Chemical-based products cover a broad spectrum of materials and forms, ranging from molecules to appliances. Table 16.1-1 shows the various product functional forms, along with examples in major application areas. Examples highlighted in italic are those discussed in this book. Most small molecules such as BTX (benzene-toluene-xyxlene) are sold to chemical and allied products industries while a limited number such as refrigerants and solvents are for sale in the consumer market. In contrast, multicomponent liquid mixtures such as liquid shampoo, semi-solids such as cream and paste, and structured solids such as controlled release herbicide are often sold directly to the consumers. Business-to-consumer sale is even more prevalent for ready-to-use devices and appliances such as diagnostic kits, drinking water filters and air cleaners. 

In contrast to the broad-spectrum herbicides, others are more selective. The phenoxy herbicides, which include chemicals such as 2,4-D, 2,4,5-T, and MCPA, are toxic to broad-leaf plants but do not affect narrow-leaf plants such as grasses. 

The use of pesticides in agriculture does not inevitably mean that food residues will result. In many cases, pesticides are applied to non-food agricultural crops, while in other instances pesticides may be applied around, but not directly on, food crops, such as the case in which a broad-spectrum herbicide is used. Even when pesticides are applied directly to food crops, food residues are often not detected. In some cases, pesticides may be applied prior to the development of edible portions of the crop, while in others the rapid environmental degradation of the pesticide between the time of application and the time of harvest may also avoid food residues. 

The product is a broad-spectrum, non-selective herbicide particularly effective against perennial weeds such as nutsedge and bindweed. Since the effect of changes in structure on biological activity is similar in several series of compounds, this topic will be discussed later. 

It is a broad-spectrum herbicide active both pre- and post-emergent. Studies with radiolabelled compounds ( ) show it to be rapidly translocated particularly to the meristematic regions. Translocation to the underground storage organs of perennial weeds prevents regrowth of these weeds. Most herbaceous and woody plants are controlled in the field at 0.4-1.0 kg a.e./ha whereas most woody plants require 0.7-3.0 kg a.e./ha (10). 

From the earliest greenhouse studies, it was obvious that AC 252,214 was an interesting compound. Remarkably, it was well tolerated by legumes, especially soybeans, yet showed a broad-spectrum of herbicidal activity, killing broad-leaved, grassy and perennial weeds. Further it was shown that AC 252,214 could be used both as a preemergent and postemergent herbicide. Rates for field application are 125-250 g/ha (12). 

The broad spectrum of biological activities, including insecticidal and herbicidal applications, of diverse molecular species containing the oxime function is discussed in several reviews published between 2001 and 2005 by Abele and colleagues . Many of these oximes are potential candidates for drugs with a number of applications as outlined in the following. 

Now we come to the other potential application of allelochemicals the development of new, safer and effective agrochemicals as pesticides and growth promoters. However, we restrict the discussion of pesticides to herbicides, fungicides, and broad-spectrum pesticides. 

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. 

There are a number of mechanisms of selectivity that are found in the herbicides that are used today. Diuron is used as a residual broad-spectrum herbicide in a number of situations such as plantations and forests. It is, however, phytotoxic to most perennial species and the selectivity shown by the established trees is because the compound does not move within the soil profile to a depth where established tree roots will absorb the compound in sufficiently high concentrations to exert an effect. This is selectivity by placement. 

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