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Dimethomorph:Mode of action,Chronic Toxicity,Carcinogenicity

May 6，2023

Dimethomorph is a fungicide with systemic function. It is used for treating mildew and root rot caused by organisms such as Pythium and Phytophthora species.

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Appearence

Colourless to grey crystalline powder

Mode of action

Dimethomorph's mode of action is the inhibition of sterol (ergosterol) synthesis. Morpholines are all systemic with curative and preventative qualities. Dimethomorph was developed for downy mildews, late blights, crown and root rots for grapes, potatoes, tomatoes, and other vegetables.

Chronic Toxicity

In the rat study, the LOAEL for systemic toxicity was 750 ppm (57.7 mg/kg/ day) for female rats based on decreased body weight and significant increase in the incidence of "ground glass" foci in the liver and 2000 ppm (99.9 mg/kg/day) for male rats based on decreased body weight and increased incidence of arteritis. The corresponding NOAEL’s are 200 ppm (11.9 mg/kg/day) for females, and 750 ppm (36.2 mg/kg/day) for males.

In the dog study at 1350 ppm, ALK phosphatase activity was increased throughout the study in both sexes (245% males, 310% females). The LOAEL for systemic toxicity is 1350 ppm, based on decreased prostate weight in males. The NOAEL was 450 ppm.

Carcinogenicity

In the rat study, dimethomorph had no significant effect on the development of neoplasms in male or female rats at the doses tested. Dimethomorph was tested at adequate doses based on significant decreases in body weight (17% and 13%) and body weight gains (27% and 14%) in females and males, respectively, in the high dose groups. The LOAEL for systemic toxicity was 2000 ppm in males and 750 ppm in females. The NOAEL's were 750 ppm (33.9 mg/kg/day) for males and 200 ppm (11.3 mg/kg/day) for females.

In the mouse study, there were no treatment-related increases in the incidence of any neoplastic lesions. The chemical was adequately tested based on decreased body weight gain (17% and 22% less than control in males and females respectively at 1000 mg/kg/day). The NOAEL for systemic toxicity was 100 mg/kg/day.

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