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Myclobutanil is a conazole class fungicide. It is used heavily to control fungi affecting wine and table grapes, especially in California. It also has a number of other food crop and commercial or residential landscaping applications. Although it has a low acute toxicity, myclobutanil has been found to affect the reproductive abilities of test animals.

(Photo by Fir0002/Flagstaffotos, from Wikimedia.)

Chemical Description

Myclobutanil is a white crystal solid. It is mobile in soil, and has a solubility in water of 142 mg/L (#EPA).

Myclobutanil is commercially available as granular dust, dry flowable, and ready-to-use formulations (#EPA).


Myclobutanil is registered for use on a wide range of food and feed crops. It may also be used in greenhouses, public rights of way, turf, and in landscaping applications. Cotton seeds may be treated with myclobutanil (#EPA).

California accounts for roughly 50% of all myclobutanil use in the US, using 70,000 to 90,000 lbs. annually. Grapes are the most heavily treated crop, using 60% of all myclobutanil in California. Almonds and strawberries are also account for a notable percentage of myclobutanil use in California (#EPA).

Human Health Effects

Myclobutanil has a relatively low acute toxicity. The acute oral LD50 for mice is 1360 mg/kg, and ranges from 1.75 to 1.8 g/kg for rats. Myclobutanil metabolizes into 1,2,4-triazole, which has a lower acute toxicity than the parent compound (#EPA).

Workers exposed to myclobutanil have reported symptoms such as skin rash, allergic dermatitis, itchiness, nausea, heachache, diarrhea, abdominal pain, vomiting, nosebleed, and eye irritation (CDPR).

In a two-generation study on rats over the effects of myclobutanil on reproduction, researchers found a decrease in pup weight gain, increased incidence of stillborns, and atrophy of the testes and prostate (#EPA). Myclobutanil is listed as a developmental toxin in the Toxics Release Inventory (#PANNA).

Chronic toxicity tests on rats found decreased body weight and changes to brain and spleen weight, in addition to reproductive effects (#EPA).

Environmental Health Effects

Myclobutanil inhibits the sterol 14-demethylase enzyme, which produces ergosterol, an organic compound vital to fungal cell wall formation (#EPA).

Myclobutanil is nontoxic to bees, which have an LD50 exceeding 362 ug/bee. It is moderately toxic to birds. The acute oral LD50 for bobwhite quail is 498 mg/kg. The primary metabolite, 1,2,4-triazole, is expected to be less toxic than myclobutanil (#EPA).

Myclobutanil is environmentally mobile. It has been found in surface water and in rain, suggesting a potential for atmospheric transport. Due to its persistence, myclobutanil may accumulate in soil with multiple applications (#EPA).


Myclobutanil is a General Use Pesticide.

Precautionary Notes

Myclobutanil can become airborne as a dust. In high concentrations, it can become an explosive mixture in the air. Burning myclobutanil may release toxic fumes (#MSDS).

Integrated Pest Management

Integrated pest management (IPM) is an approach to pest management that can significantly reduce pesticide use. Widely used in agriculture, landscape maintenance, and structural pest control, it emphasizes prevention and monitoring of pest problems and considers pesticide applications only when nonchemical controls are ineffective or impractical. To learn more about IPM, see Toxipedia's sister site IPMopedia, which includes information on control of fungal diseases.



California Department of Pesticide Regulation. Tolerance Evaluation of Myclobutanil: Strawberries and Asparagus. (August 2000). [Accessed 9-3-10].

Dow Agrosciences. Material Safety Data Sheet: Myclobutanil. (September 2003). [Accessed 9-3-10].

Environmental Protection Agency. Risks of Myclobutanil Use to Federally Threatened California Red-legged Frog. (June 2009). [Accessed 9-10-10].

Pesticide Action Network North America. Myclobutanil. [Accessed 9-3-10].

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