Weed-killers

A great number of various substituted aminophenyl derivatives of thiazolium, and their organic or metallic complexes, have been patented as weed-killers or regulating growth factors of plants (135-138). 

Weber numbers Weber s law Web formation Web knitting Web offset inks Webster hardness gauge Weed killers... 

In North America, calcium cyanamide is no longer used as fertiliser, but it has limited use in special agricultural appHcations for defoHants, fungicides, herbicides, and as a weed killer. The primary industrial use is as a chemical intermediate for the manufacture of calcium cyanide, hydrogen cyanamide solution, and dicyandiamide. Calcium cyanamide is also used to add nitrogen to steel. 

Acetylene and ethylene compete as a chemical raw material. Ethylene is generally more economical, resulting in declining use of acetylene as a raw material. Calcium carbide, a raw material for acetylene has other uses. Treated with nitrogen, it gives calcium cyanamide, valuable as a fertilizer and weed killer, and a raw material for the production of melamine, used ir ng some modern plastics. 

CaNCN is used as a direct application fertilizer, weed killer, and cotton defoliant it is also used for producing cyanamide, dicyandiamide and melamine plastics. Production formerly exceeded 1.3 million tonnes pa, but this has fallen considerably in the last few years, particularly in the USA where the use of CaNCN as a nitrogenous fertilizer has been replaced by other materials. In 1990 most of the world s supply was made in Japan, Gennany and Canada. 

Its salts are used in flame retardants, weed killers and for electroplating. 

Another interesting case is that of a manufacturer who recommended use of 2,4-D weed killer as a selective spray for control of weeds in young carrots. He had previously... 

Addition of ammonium chloride to a drum of weed-killer was suspected as the cause of a violent explosion (involving formation of ammonium chlorate) [1]. Mixtures, used for smoke compositions, are hazardous [2],... 

Shoes became contaminated with a chlorate weed-killer solution which dried out in wear. A welding spark later fell into the shoe and the front was blown off. 

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). 

Alternate names Chem-Penta, Chemtrol, Chlorophen, Dow Pentachlorophenol, Dowicide 7, Dowicide EC-7, Dowicide G, DP-2, Durotox, Lauxtol A, OntrackWE-1, PCP, Penchlorol, Penta, 2,3,4,5,6-pentachlorophenol, Penta General Weed Killer, Pentacon, Penta-kil, Pentanol, Pentasol, Penwar, Permacide, Permaguard, Permasem, Permatox, Priltox, Santobrite, Santophen, Sinituho, Term-l-trol, Weed-Beads, Weedone... 

It sometimes appears that animals, especially cattle, develop an increased preference for weeds sprayed with an arsenic weed killer, not because of a change in the palatability of the plant, but probably because arsenic compounds are salty and thus attractive to animals (Selby et al. 1977). 

Cranberry scare (1959, US) Use of aminotriazole, weed killer, thyroid cancer scare... 

Most common weed killers work by poisoning the root of the plant. 

Ammonium thiocyanate is used as an ingredient in antibiotic preparations, pesticides, liquid rocket fuels, adhesives, and matches. It is also used in photographic processes, to improve the strength of silks, and as a weed killer. 

Thiocyanates are present in water primarily because of discharges from coal processing, extraction of gold and silver, and mining industries. Thiocyanates in soil result from direct application of weed killers and disposal of by-products from industrial processes. Less important sources include release from damaged or decaying tissues of certain plants such as mustard, kale, and cabbage. 

Chemical weed control in cacao plantations with volatile weed killers is generally considered detrimental to pollinating insects and to the flower and fruit set. Recently Naundorf (28) and Oliver (33) in Colombia conducted tests with compounds derived from 2,4-D and with an ammonium salt of dinitro-o-cresol to determine the effect of these materials on the flowers. They found that dinitro-o-cresol can be used at the dosages commercially recommended, and that only the volatile 2-4-D derivatives at concentrations of 500 to 750 grams per plaza (6400 square meters) can be used. 

In many crops where weed killers are used, applications must be made with care or the crop being weeded may suffer. This takes some attention. Coffee showed characteristic injuries (22, 51) from applications of the weed killers 2,4-D, TCA, and CMU [3-(p-chlorophenyl)-l,l-dimethylurea]. On the other hand, as in other tree crops, further work on coffee proved that, if properly handled, weed sprays did not result in important permanent harm to the trees. Some of the most recent work has shown (22) that amine salts and butoxyethanol esters of 2,4-D caused less... 

In the past 10 years, chemical weed killers have replaced the machete and the hoe to a large extent in the tropics, especially in sugar cane fields. More than any other chemical, 2,4-D and its derivatives are used. Herbicides could also be used profitably to a greater extent in crops such as pineapple, rubber, rice, coffee, pastures, and lawns. Methods and chemicals used in Puerto Rico are described and results are compared with other areas. 

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