Insecticidal classes, market

Figure 24.1 shows the major insecticidal classes and their market share in 2003. The global insecticide market is forecast to decline in value by 1.3% per annum until 2007. This represents a fall in the overall agrochemical market share from 27.5% in 2002 to 25.7% in 2007 [15]. 

Neonicotinoid insecticides have experienced a most remarkable and steady increase in use since their market introduction in 1991, now exceeding 10% of the total insecticide market 1-3). An overview of these products is given in Table I (cf. 4). The major advantages of the new products over the previously preferred organophosphates are a novel chemistry, a new mode of action, systemic action and human safety. The systemic activity makes them the insecticide class of choice for the control of plant sucking pests. 

Pyrethrins and pyrethroids are probably the best known and safest classes of natural or synthetic insecticides, widely used in domestic and agricultural applications (1-7). Pyrethrins are natural insecticides derived from the Chrysanthemum cineraria flowers the plant extract, called pyrethrum, is a mixture of six isomers (pyrethrin I and II, cinerin I and II, jasmolin I and II) which was first used in China in the century AD, during the Chou Dinasty. The world pyrethrum market is worth half a billion US dollars [main producers are East Africa highlands (Kenia, Tanzania and Rwanda) and Australia] however, its availability is subject to cyclical trends, due to rains and relations with farmers, who face high harvest costs also due to the fact that the flowers have to be... 

The fact that nature has chosen to use a cyclopropane skeleton to design a defense mechanism for certain pyrethrum flowers against insect attack has been known since 1924, when Staudinger and Ruzicka isolated and characterised (-t-)-Jrans-chrysanthemic acid 1 from the petals of these plants [1]. The active insecticidal ingredients in these plants are in fact esters of 1, which can be easily modified and which have been commercially exploited to give birth to one of the most successful classes of biomimetic insecticides, the pyrethroids. In 1997, the market value of this class of insecticides amounted to a staggering 1.5 billion US [2],... 

There seems to be no limit to the number of toxic organophosphorus compounds that can be synthesized and that exhibit insecticidal activity. While many compounds of this type have been marketed, only about 20 of them comprise the bulk of the total tonnage. Parathion, methyl para-thion, and malathion are perhaps the best known and most widely used of this class of insecticides. The relatively low cost of the first two, combined with their good performance against a broad spectrum of insects, probably accounts for their continuing popularity. The low order of toxicity of malathion to mammals has made it acceptable under many conditions where other, perhaps more insecticidally active, insecticides are restricted. 

Figure 1.1 Major chemical classes of insecticides and their global market share in 2004. (Adapted from Nauen, R., Pest Manag. Sci., 62, 690, 2006.)...

Neonicotinoids are a new class of synthetic insecticides that became commercially available in the 1990s. Currently there are only a few neonicotinoid insecticides on the market but those are being increasingly used with a good prognosis for their further development. These new-generation pesticides have potential as replacements for some of the more toxic organophosphorus and methylcarbamate insecticides. 

However, when classifying the presently available crop protection products of substantial commercial importance, one hnds only a comparatively low number of biochemical modes of action for which compounds have been commercialized. Altogether, four modes of action account for more than 75% of the current insecticide sales (Figure 1). In the helds of herbicides and fungicides, the situation is similar. Here six different modes of action dominate each market. Of these, several represent modes of action that have been commercialized during the last decade. Further classes of compounds demonstrating other modes of action which have been identihed in the past in all three indications have not gained major market shares from an economical point of view. 

Organophosphates (OPs) were first introduced to the agrochemical market in 1944 and are economically still the most successful and diverse chemical class of insecticides ever invented [4]. Over 100 different active ingredients belonging to this class are known, with the best selling OP of all being chlorpyrifos. 

Fig. 24.1. Major chemical classes of insecticides and their market share.

Pymetrozine (1 developmental code CGA 215 944) is an insecticide, highly active and specific against sucking pests. It is the only commercial representative of the chemical class of the pyridine azomethines. Pymetrozine is marketed by Syngenta under the trademarks of Chess , Plenum, Fulfill , Relay , and Sterling [1-4]. 

Given the disadvantages mentioned before, the manufacture of chrysanthe-mic acid is economically less important than that of permethric acid. Scientifically, the syntheses of both compounds are ofinterest. The aim of (mostly industrial) research was to identify the simplest and cheapest way to access this structurally demanding class of substances. Nowadays, pyrethroid research is however largely a matter of the past, the insecticide market is dominated by... 

Today, the neonicotinoids are reckoned as the most important class of insecticides in the crop protection market. Many smart syntheses have been published. 

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