Fosetyl-aluminium

In conclusion, available data suggest that cymoxanil has an unknown fungicidal mode of action and might also induce some host plant defense responses (similar hypersensitive effects are known from many fungicides, triazoles, car-boxin, strobilurins, etc.). 

Another fungicide of high market significance with efficacy mainly against Oomycetes is fosetyl-aluminium. It was developed by Rhone-Poulenc, now Bayer CropScience. The first market introduction was in 1977. 

One related compound, the corresponding sodium salt (fosetyl-sodium), also reached an advanced stage of development as an Oomycetes fungicide, however did not make it to market introduction. Moreover, other salts and the parent compound itself, ethyl phosphite or fosetyl, are also active against Oomycetes. 

Due to the fact that the compound is a salt, the water solubility of fosetyl-aluminium is extremely high. It is stable towards hydrolysis under neutral conditions and decomposes only under strong acidic or basic conditions or by exposure to strong oxidizing agents. Table 21.3 lists further physicochemical properties [23]. 

Water - 120000 Acetone = 13 Acetonitrile = 5 Ethyl acetate = 5 Hexane = 5 Methanol = 920 Propylene glycol = 80 

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Fosetyl. Fosetyl (aluminium ethyl phosphate Figure 4.32) is a specific downy mildewicide (Oomycetes) used to control Plasmopara viticola in vines and Phytophthora blights in various fruit and nut crops. 

Fosetyl-aluminium phosphoro organic, phosphonate Fosmethilan phosphoro organic, phosphoro dithioate, amide... 

Phosphorus tribromide brodifacoum, difenacoum, fenpropidin, flocoumafen, pyriproxifen Phosphorus trichloride chloretoxyfos, disulfoton, EPN, ethephon, ethoprop, fonofos, fosamine ammonium, fosetyl aluminium, fosthiazate, glufosinate, glyphosate, isofenphos, merphos, propaphos, sulprofos, SSS-tributyl phosphorotrithioate, trichlorfon, trichloronat Phthalic acid pindone, tecloftalam... 

Despite intensive efforts to elucidate the mode of action of new fungicides, in some cases the biochemical target of a new compound remains unclear. This chapter describes five compounds with unknown mode of action, cymoxanil, fosetyl-aluminium, flusulfamide, diclomezine and triazoxide. 

Fosetyl-aluminium belongs to the chemical class of phosphonates and was discovered in 1973 by Philagro [22]. The lUPAC chemical name is aluminiumethyl-hydrogenphosphonate (CAS-RN. 39148-24-8). Figure 21.2 shows its chemical structure. 

According to a patent application published in 1996 [24] (Scheme 21.2) fosetyl-aluminium can be prepared by combining phosphorus trichloride with a stoichiometric amount of ethanol (85-100%) at temperatures below 20 °C followed by... 

Table 21.4 Fosetyl-aluminium - use against plant diseases of highest market significance.

Fosetyl-aluminium is mainly used in grapes, vegetables, citrus and tropical fruits such as pineapple. The use of fosetyl-aluminium to control the plant diseases of the highest market significance are listed in Table 21.4 [27]. 

Due to its fast degradation in plants [5-6], animals [28] and in the environment, where it is metabolized rapidly into phosphate, the toxicological and eco-toxicological profile of fosetyl-aluminium is very favorable (acute oral toxicity rats LDso = 5800 mg kg day ), leading to a classification in WHO toxicity class V (unlikely to be hazardous). 

Although this compound has been intensively used for nearly 30 years, resistance development of fungal pathogens to fosetyl-aluminium is very limited. Some studies, though, indicate a significant decrease in sensitivity of Plasmopara viticola to fosetyl-aluminium with resistance factors between 5 and 24 [29]. Moreover, decreased sensitivity against lettuce downy mildew, Bremia lactucae, has been observed [30]. However, resistance development to fosetyl-aluminium seems to have only a limited impact on the overall product performance. 

The abundant literature on the biochemical mode of action of fosetyl-aluminium produced during the 1980s has been thoroughly reviewed [16, 35-37], leading to the conclusion that fosetyl-aluminium and phosphonate, the in planta metabolite of fosetyl-aluminium, both have a direct and an indirect mode of action. 

In conclusion, fosetyl-aluminium (phosphonate) is a potent inducer of several plant defense responses in addition to its limited direct effect on fungal metabolism. 

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