|Pesticide Type||Fungicide (Group M)|
|Chemical Class||ethylenebisdithiocarbamate (EBDC)|
|Common Trade Names*||Manzate®, Dithane®, Penncozeb®, Fore®, Roper®|
|Registration Status||EPA: Registered since 1948
*No endorsement is implied in the referencing of trade names.
Mancozeb is a broad-spectrum contact fungicide which is labeled for use on many fruit, vegetable, nut, and field crops in Minnesota. It provides protection against a wide spectrum of fungal diseases, including potato blight, leaf spot, scab, and rust. It is also used as seed treatment for potatoes, corn, sorghum, tomatoes, and cereal grains. In 2017, approximately 1.1 million pounds of mancozeb were sold in Minnesota.1
Mode of Action
Mancozeb is classified by the Fungicide Resistance Action Committee (FRAC)2 as a mode-of-action group M, multi-site, fungicide. It interferes with enzymes containing sulphydryl groups, disrupting several biochemical processes within the fungal cell cytoplasm and mitochondria.
Issues with Resistance
As a Group M fungicide, mancozeb has a low risk of resistance development due to its multi-site activity on fungal pathogens. It is often tank mixed with single-site fungicides to help with resistance management.
Mancozeb Movement in the Environment
Mancozeb and other EBDC fungicides (maneb, zineb, metiram) are water insoluble and bind tightly to soil. They are rapidly hydrolyzed, (soil half-life (t 1/2), 1 day) to ethylene bis isothiocyanate (EBIS), ethylene thio urea (ETU), ethylene urea (EU), hydantoin (HYD), and other minor degrades.3 These products then undergo microbial degradation. The aerobic soil half-lives of EBIS, ETU, EU, and HYD is less than three days.4 These products are water soluble and have moderate soil adsorption indicating that soil mobile may occur under some conditions. ETU is a common degradate of all EBDCs including mancozeb. ETU, a group B2 carcinogen, was established to be the drinking water stressor resulting from the use of all EBDCs3. Current water tests typically analyze for ETU rather than the short-lived parent compounds.
Detection in Minnesota Waters
The MDA does not currently test for ETU. Analysis for this chemical cannot be incorporated into the existing procedures used by the MDA laboratory and would require additional analytical methods or laboratory equipment.
In a study conducted in Florida and Georgia, ETU was analyzed in 1,075 samples, 50 groundwater and 1,025 surface water. ETU was not detected in groundwater. It was detected in four surface water samples collected from canals with a maximum detection of 1,089 ug/L. This is less than 1% of the lowest OPP benchmark (134,500 ug/L).5
Mancozeb and Non-target Organisms
Mancozeb is slightly toxic to birds on an acute basis, while ETU is practically non-toxic to birds. The 14-day LC50 for ETU to bobwhite quail is greater than 2,250 mg/kg-bw.5 Mancozeb and ETU are highly toxic to freshwater fish. The 96 hr LC50 for ETU to freshwater fish is 0.91 mg/L. ETU is moderately toxic to aquatic invertebrates with 48 hr EC50=1.04 mg/L. Mancozeb has a very low acute toxicity to mammals. Oral LD50 values for mancozeb ranges from 4,500 to 11,200 mg/kg in rats.5
Mancozeb and Human Health
Since mancozeb is not expected to remain in drinking water long enough to reach a location that would supply drinking water for human consumption, whether from surface or groundwater sources, this is not a likely exposure route. Estimated concentrations of ETU, for both surface and ground water sources of drinking water, were below EPA’s level of concern.6 Minnesota Department of Health developed rapid assessment value for ETU is 2.0 µg/L.
Major routes of exposure to mancozeb are through the skin or from inhalation. In spray or dust forms, the EBDCs and ETU are moderately irritating to the skin and respiratory mucous membranes. Symptoms of poisoning from this class of chemicals include itching, scratchy throat, sneezing, coughing, inflammation of the nose or throat, and bronchitis. This concern can be reduced by using proper application techniques. There are risk concerns for some occupational handlers which can be mitigated with use of appropriate personal protective equipment.7
Updated November 2020.
2Fungicide Resistance Action Committee. 2023. FRAC Code List: Fungal control agents sorted by cross resistance pattern and mode of action.
3Housenger, J., M. Shamim, S. Snyderman. 2015. Registration review - problem formulation for the ecological risk assessment and drinking water exposure assessment to be conducted for mancozeb. USEPA.
6US Environmental Protection Agency. 8/2005. Reregistration Eligibility Decision (RED) for Maneb. EPA 738-R-05-XXX.
7US Environmental Protection Agency. 2002 EPA Region 8 Worker Protection Standards. Symptoms of exposure to pesticide products used on minor Colorado crops. www.epa.gov/sites/default/files/documents/pestsymptoms.pdf.