Understanding and Managing Sudden Oak Death in California

SIDEBAR 3-1—Cleaning Contaminated Tools and Equipment

If possible, clean tools, equipment, shoes, vehicles, and other items that may have become contaminated with P. ramorum inoculum in soil or debris before leaving the infested location. If cleaning is done at a generally  infested site, inoculum can be brushed and/or washed from the contaminated surfaces; the contaminated material does not need to be collected and destroyed. Cleaning should be done on a surface that is unlikely to allow cleaned materials to become recontaminated, such as pavement, a plastic tarp, or a continuous layer of gravel.

Simply spraying disinfectants on contaminated surfaces is not effective for killing P. ramorum inoculum that is present in large pieces of plant tissue or thick layers of soil. Thorough cleaning of debris and soil from equipment, tires, and shoes is necessary to remove P. ramorum propagules. Compressed air can be used to help blow debris and soil out of tools and equipment such as chainsaws and chippers. Debris and soil can also be brushed or swept from surfaces. Surfaces with clinging mud or damp debris may need to be washed off. Use a brush and clean, noncontaminated water to thoroughly remove dirt from surfaces. An appropriate cleaning agent can be used after removing large particles of debris and soil to provide a higher level of protection. Detergent solutions, diluted bleach, and ethanol or isopropyl alcohol (70% or higher) can facilitate cleaning of contaminated surfaces and may directly kill exposed spores. Some formulated products, such as Lysol® Disinfectant Spray (79% ethanol), can be used for this purpose. Allow wet surfaces to dry thoroughly to further reduce the chance that any P. ramorum propagules will survive.

If it is not possible to completely clean items such as shoes or hand tools at the infested area, these items may be placed in plastic bags for later cleaning at an indoor site such as a utility sink. It is important to make sure that all potentially contaminated material is washed down into the sanitary sewer system (not into stormwater drains) or is sealed in bags that will be sent to a landfill.

Disinfecting with diluted bleach. Standard commercial bleach (5.25% sodium hypochlorite) diluted to 10% strength (1 part bleach, 9 parts water) may be used as a disinfectant for hard surfaces. For concentrated ("ultra") bleach (6.15% sodium hypochlorite, EPA Reg. No. 67619-8), the corresponding dilution ratio is about 1 part bleach to 10.5 parts water. Equipment to be disinfected needs to be maintained in contact with the bleach solution for at least a minute to kill P. ramorum propagules. Longer contact times and more thorough soaking will be needed if large pieces of debris are present. Use fresh bleach solutions and change them if they get heavily contaminated. Bleach solutions lose potency over time and are deactivated with use.

Concentrated bleach and hypochlorite solutions are corrosive and need to be handled with care, using both eye and skin protection. Bleach solutions can also react with various chemicals to release toxic chlorine gas and other hazardous chlorinated gases. Bleach solutions can corrode steel, and are not advisable for equipment such as chainsaws.