Resistance dicarboximides

Laboratory tests with M. fructicola (26) and field experience with the dicarboximides for Botrytis control in strawberry fields (14) suggest fungicide resistance may be a problem if the dicarboximide fungicides are used extensively and continuously season after season. Although many workers consider dicarboximide resistant strains less fit than wild-type strains ( 1 6, 17 ), the research suggests that field resistance will develop if steps are not taken to... 

Dicarboximide Resistance Research and Management Goals and Their Implementation in Worth America... 

In Botrytis, dicarboximide and phenylpyrrole resistant laboratory strains [12,18] and less sensitive field isolates [13, 19] are usually found to be mutated in Dafl, the histidine kinase homologous to Os-1. However, field isolates less sensitive to dicarboximide fungicides were reported to retain wild-type levels of sensitivity to phenylpyrroles [18-20]. Vignutelli et al. [21] crossed a field resistant strain of Botrytis with a sensitive one and found that dicarboximide resistance segregated separately from phenylpyrrole resistance, suggesting different genes regulate... 

Well over 100 plant pathogens have become resistant to various fungicides under field conditions. Failure of the acyl alanines, benzimidazoles, thiophanates, carboxanilides, dicarboximides, hydroxypyrimidines, some organophosphates, and most of the antibiotics has occurred. In other cases, a moderate decrease in sensitivity without a rapid loss of disease control has been observed as in the case of sterol biosynthesis inhibitors (triazoles, pyrimidines, and imidazoles) and organophosphates. The most effective approach is to use fungicides having different modes of action in combination,... 

Thus, they prevent an arrangement of the spindle apparatus. The tubuline-benzimidazole-interactions have been studied in detail (.6). It is known that carbendazim, for example, after entering the nucleus, specifically binds to the 3 -subunit of tubuline and by this inhibits the dimerization of the a and 3 -subunits to a functional tubuline unit. Resistant strains possess altered 0 -subunits with a decreased affinity for benzimidazoles (7). The modes of action of other inhibitors of mitosis, like dicarboximides, aromatic hydrocarbons, or dithiocarbamates, have not yet been precisely described on a molecular basis. 

The ultimate cause of fungal toxicity upon treatment with dicarboximides, phenylpyrroles and perhaps aromatic hydrocarbon fijngicides such as chloroneb, may be an overproduction of osmoregulating polyols. Laboratory mutants defective in the os-1 gene, which encodes an early osmosensing kinase, are resistant to all three classes of fungi-... 

Dicarboximides. Acute problems of resistance to dicar-boximides can arise when the products are intensively and exclusively used over many seasons. Resistant isolates are moderately resistant and tend to be less fit than... 

Determine genetic control and biochemical modes of action/resistance for DMIs and dicarboximides. 

Determine the efficacy of dicarboximides in the presence of various proportions of resistant strains. Degrees of continued efficacy have been noted despite the occurrence of substantial resistance. 

Determine the effects of dicarboximides and/or companion fungicides on the pathogenicity of selected resistant isolates. 

Link some product uses to monitoring programs. Label restrictions could prevent the use of dicarboximides in high-resistance areas. 

Develop common label statements to warn of resistance and restrict the use of other dicarboximides with cross-resistance. 

Considerable interest is given nowadays to the possibility of using natural products as parasiticides in agriculture to replace or enhance phytochemical products, because of the serious environmental problems caused by the often indiscriminate use of pesticides. Massive use of synthetic fungicides against parasites has led to the appearance of strains which are resistant to both the dicarboximide derivatives (iprodione, procymidone, vinclozolin [64-65] and the benzimidazoles (benomyl, carbendazim, thio-phanates, etc.) [66-67] making it much more difficult to control the pathogens. 

Dicarboximides are still used against Botrytis cinerea and related pathogens in a range of crops although resistance was reported repeatedly. However, resistance... 

The inherent risk for development of resistance towards phenylpyrroles is considered as medium [39]. No cross-resistance has been reported between phenylpyrroles and products of other chemical classes, including benzimidazoles, dicarboximides, N-phenylcarbamates and anilinopyrimidines for B. cinerea [40]. 

Recently, multiple resistance of Mtemaria brassicola isolates [41] towards phenyl-pyrroles and dicarboximides was observed however, the underlying mechanisms need further clarification. Although reduced sensitivity of B. cinerea lab mutants [42] and field isolates [43] to phenylpyrroles have been observed in a very few cases, no losses in the performance of the solo or the mixture product were observed under practical commercial conditions. 

The routine monitoring conducted in commercial vineyards in Qiampagne, France, revealed the presence of resistance to benzimidazoles, dicarboximides and anilinopyrimidines in grapevine grey mold (15), Ifowever, the limitation in the use of these three families of botryticides prevents the build-up of resistant populations. 

---