Dazomet is a chemical compound widely used in agriculture as a soil treatment. It functions as a broad-spectrum biocide, helping manage various pests that can hinder plant growth and crop production. This compound is a synthetic organic chemical, specifically a dithiocarbamate pesticide.
Understanding Dazomet’s Nature and Action
Dazomet is supplied in granular or powder formulations, appearing as an off-white to yellowish solid with a sulfurous odor. It is classified as a soil fumigant. Dazomet itself is not the active pesticidal agent; rather, it acts as a precursor.
Upon contact with moist soil, dazomet undergoes a chemical decomposition process. This breakdown releases methyl isothiocyanate (MITC), the primary active compound responsible for its fumigant properties. MITC is a volatile gas that diffuses through soil pores. Its effectiveness is influenced by soil moisture, temperature, and the method of incorporation. Dazomet requires soil temperatures between 10-12°C and 22-25°C for optimal activation; excessively high temperatures can lead to too rapid a release and reduced effectiveness.
Key Uses in Soil Management
Dazomet’s primary application is as a pre-plant soil treatment in various agricultural and horticultural settings. It is used to prepare planting beds by controlling a wide array of soil-borne pests before crops are established. This broad efficacy helps prevent diseases and improve overall crop yield.
The compound controls nematodes, microscopic roundworms that damage plant roots. It also targets soil-borne fungi, including common pathogens like Fusarium, Pythium, and Rhizoctonia, which cause root rots and wilts. Additionally, dazomet is effective against germinating weeds, weed seeds, and several soil insects, such as wireworms and cutworms.
It is applied in environments such as:
- Vegetable fields (e.g., tomatoes, carrots, cucumbers, lettuce)
- Ornamental plant nurseries
- Tree nurseries
- Greenhouses
- Turf sites
- Golf courses
- Tobacco seedbeds
Health and Safety Precautions
Exposure to dazomet and its breakdown product, MITC, can occur through inhalation, skin contact, eye contact, and ingestion. Inhalation of MITC vapor, even at low concentrations, can cause irritation in the nose and upper respiratory tract, causing coughing, wheezing, or shortness of breath. Higher concentrations may result in burning sensations, headaches, dizziness, and nausea.
Skin contact with dazomet can cause irritation and, with prolonged exposure, possible burns. MITC, the degradation product, is a known dermal sensitizer, meaning repeated contact can lead to allergic skin reactions. Eye contact with dazomet can cause severe irritation and burns, with a risk of serious, irreversible effects. Ingestion, while not a primary route of exposure, can lead to irritation of the mouth, throat, and esophagus, and is considered harmful.
To minimize risks, personal protective equipment (PPE) is recommended during handling and application. This includes:
- Chemical-resistant gloves
- Protective eyewear (safety glasses or goggles)
- Long-sleeved clothing
- Respirators (to prevent inhalation of vapors and mists)
Proper ventilation in enclosed spaces like greenhouses is important. Restricted entry intervals into treated areas must be observed to allow MITC to dissipate before workers can safely re-enter.
First Aid Measures
In case of accidental exposure:
- Inhalation: Move individuals to fresh air; if breathing is difficult, artificial respiration may be needed.
- Skin Contact: Remove contaminated clothing and rinse the affected area thoroughly with large amounts of water and soap.
- Eye Contact: Remove contact lenses and flush eyes immediately with plenty of water for at least 15 minutes. Seek prompt medical attention.
- Ingestion: Rinse mouth with water and seek medical attention without inducing vomiting unless directed by a professional.
Environmental Considerations and Oversight
Dazomet’s use can impact non-target organisms within the soil ecosystem. While it is designed to control pests, the active compound MITC is highly toxic and can disrupt the biological functions of beneficial soil microbes. There is a potential for adverse effects on aquatic life if runoff or leaching carries dazomet or MITC into water bodies. MITC is acutely toxic to aquatic invertebrates and fish.
The persistence of dazomet and MITC in the soil environment is influenced by soil moisture, temperature, and organic matter content. Dazomet is highly soluble in water and somewhat volatile. The primary route of dissipation for MITC from the atmosphere is rapid photolytic decomposition. Regulatory bodies, such as the Environmental Protection Agency (EPA) in the United States, oversee the registration and use of dazomet to mitigate ecological harm. These agencies implement measures such as restricted use classifications, buffer zones around application sites, and maximum application rate reductions to minimize exposure to non-target organisms. Data requirements for ecotoxicity and environmental fate are part of the regulatory review process.