Rotenone Insecticidal properties

Tremetone (17) seems also to have insecticidal properties 27,30a,1> similar to those of rotenone (13)31 (and half its ichthyotoxic action). It should be noticed that the structure of tremetone is similar to rings C, D, and E of rotenone. 

Chemicals have been used to kill or control pests for centuries. The Chinese used arsenic to control insects, the early Romans used common salt to control weeds and sulfur to control insects. In the 1800s pyrethrin (i.e., compounds present in the flowers of the chrysanthemum, Pyrethrum cineraefolium) was found to have insecticidal properties. The roots of certain Derris plant species, (D. elliptica and Lonchocarpus spp.) were used by the Chinese and by South American natives as a fish poison. The active ingredient, rotenone, was isolated in 1895 and used for insect control. Another material... 

Currently pest control by natural plant extracts is practiced primarily by subsistence farmers in those less developed part of the world where it is still an economic necessity.(ref. 3). Of the approximately 2000 plant species with known insecticidal properties (ref. 4), few have been developed commercially. These include the pyrethrins, rotenones and some of the alkaloids. Pyrethrins were the most important natural plant extracts in the early commercial insecticide formulations and were already in use in Persia and Yugoslavia during the early 1800s. By 1939 pyrethrum imports to the United States were 13-5 million lbs, declining from this peak as the synthetic analogs (e.g., the allethrins) appeared on the market. The addition of stabilizers (antioxidants) and synergists to the original pyrethrum formulations saved the natural product from commercial extinction. Currently the demand for pyrethrum flowers is still over 25,000 tons per annum—met by hand-harvested crops from Ecuador, Kenya and Tanzania (ref. 5) ... 

Several nerve toxins produced by plants are interesting because of their insecticidal properties. Insecticidal nicotine is extracted from tobacco. Rotenone (Figure 19.2) is synthesized by almost 70 legumes. This insecticidal compound is safe for most mammals, with the notable exception of swine. The most significant insecticidal plant derivatives, however, are the pyrethrins, discussed below. 

Rotenone s insecticidal property is broad spectrum, so beneficial insects are killed on contact along with the pests. It is moderately toxic to people and most animals and very toxic to swine, birds, and fish. Some people are highly allergic to rotenone on food crops and suffer from violent reaetions even after a week-long post-spray period, sometimes even after the food has been cooked. New evidenee suggests that rotenone may cause growth abnormalities in laboratory animals. 

Rotenoids are effective inhibitors of oxidative phosphorylation in animal mitochondria this effect is responsible for the insecticidal properties of this group of compounds (Williams and Harbome, 1989b). This effect may occur at concentrations as low as 24 nmol/g of mitochondrial tissue. The lethal dose of rotenone in the silkworm is 0.003 mg/g body weight (Harbome, 1991). This series of compounds also inhibits other enzymes (McClure, 1975). 

The heavy rates of application of such materials as lead or calcium arsenate, was ill suited to the type of application equipment then available. It must be remembered that aerial application of chemicals in forestry came with the improved planes after World War II. Rotenone and pyrethrum, two insecticides used in agriculture in that era, had but limited applicability in forestry because of their properties (10). 

Rotenone is present in the roots of Derris spp., from Malaya and the East Indies, and Lon-chocarpus spp. Rotenone is a selective insecticide with some acaricidal properties for control of garden insects, and lice and ticks on animals. Rotenone is very toxic to fish, so it can be used to control undesirable fish species (to eradicate them from lakes, streams, and reservoirs). Its oral LD50 in rats is 132 mg/kg. 

Since the 1920s several research workers have investigated the insecticidal effect of various thiocyanates. The action of these compounds is characterised by the knock-down effect and by the contact character of action. They have therefore mostly been used in combination with other insecticides, such as rotenone, pyrethrum and DDT. From the end of the 1940s onwards their use was gradually discontinued, due mainly to their disagreeable odour and their phytotoxic and skin-irritating properties. 

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