Welcome to the Department of Pesticide Regulation

Soil Moisture and Tarpaulin Repair

Back to Field Fumigation Methods Allowed Under the New Regulations

Regulations on field fumigant applications that went into effect in January 2008 are designed to reduce emissions of smog-producing compounds from fumigant pesticides. The rules focus on field fumigant applications made between May 1 and October 31 in five nonattainment areas (NAAs) that do not meet federal air quality standards for pesticide VOC emissions: the San Joaquin Valley NAA, Sacramento Metro NAA, South Coast NAA, Southeast Desert NAA, and Ventura NAA.

In these areas, only certain application methods listed in regulation can be used. Many application methods also include requirements for soil moisture and tarpaulin repair.

Soil Moisture

Soil moisture is critical in controlling emissions for several application methods.

  • If specified, follow the label requirements for soil moisture.
  • If the label does not specify soil moisture, the regulations require a minimum amount of soil moisture above the depth of application. The specific amount of moisture depends on the soil texture, and is determined using the “feel” test:
    • Coarse soils (sand and loamy sand) – must have enough moisture to form a ball when compressed by hand, that may break when tapped.
    • Loamy, moderately coarse, or medium textured (coarse sandy loam, sandy loam, fine sandy loam) – must have enough moisture so that soil forms a ball that holds together when tapped.
    • Fine texture soils (clay loam, silty clay loam, sandy clay, silty clay, sandy clay loam and clay) – must have enough moisture so that the soil is pliable, not crumbly; forms a ribbon when squeezed between thumb and forefinger.
    The specific requirements are detailed in the regulations. [Scroll to sections 6448.1(b), 6449.1(c), and 6450.1(b).]

These requirements reflect at least 25% available soil moisture, as described in “Estimating Soil Moisture by Feel and Appearance,” (PDF, 661 kb) published by the U.S. Department of Agriculture.

Tarpaulin Repair

An intact tarpaulin is a critical element in reducing VOC emissions for several fumigant application methods. Therefore, the tarpaulin repair requirements previously required for methyl bromide field fumigations now apply to other fumigants.

The regulations specify that, if a tarpaulin is used, the operator of the property must maintain a “tarpaulin repair response plan.” The plan must identify the responsibilities of the licensed pest control business and/or the permittee with regard to detecting and repairing tarpaulin damage.

At a minimum, the tarpaulin repair response plan shall indicate who is responsible for the repair and the criteria used to determine when repairs are needed. The criteria include one or more of the following elements:

  • hazard to the public, residents, or workers.
  • proximity to occupied structures.
  • size of the damaged area(s).
  • timing of damage.
  • feasibility and response time of repair.
  • and environmental factors such as wind speed and direction.

The specific requirements are detailed in the regulations. [Scroll to sections 6448.1(d), 6449.1(d), and 6784(b)(5).]



For content questions contact:
Randy Segawa
Phone: (916) 324-4137
E-mail: rsegawa@cdpr.ca.gov