sanitation

If reforesting an area impacted by SOD with local acorns, what can be done to prevent spreading the pathogen during planting?

Take the following precautions when using local acorns for oak reforestation projects in areas impacted by SOD to help minimize pathogen spread.

  • Place acorns in a 10% dilution of bleach for 10 minutes then rinse twice with tap water.
  • Make sure volunteers’ shoes are free of soil, mud, and organic material.
  • Be sure tools being used are clean and free of soil, mud, and organic material.

 

How long can Phytophthora ramorum survive in wood chip mulch?

Survival of P. ramorum (SOD pathogen) in wood chips depends on a few factors:

  • Were the chips allowed to become wet?
  • What size are the chips?
  • Is green waste present?
  • What time of year was the wood chipped?
  • Where in California are the chips located?

Chips that are piled wet or tarped and include infected green waste (e.g. bay laurel leaves) may support pathogen viability for over 1 year, especially in mild coastal areas. If the wood is chipped in the summer and early fall and the chips are not piled, but rather broadcast in a 1-inch layer in a dry and sun-exposed area, pathogen viability may only be supported for a few weeks, especially if in hotter interior areas.

How long can Phytophthora ramorum survive in soil moved from an infested area?

Survival of P. ramorum (SOD pathogen) in dead hosts or non-plant substrates is extremely variable and strongly affected by climatic factors. Although a comprehensive study on this topic has not conducted, extrapolating from several studies we can say the following:

Soil becomes more infectious from late winter to early summer in the presence of rainfall, so any movement of soil away from a SOD-infested area from January to July could transport viable P. ramorum.

Keep the following in mind:

  • The larger the volume of soil moved, the greater the risk.
  • In organic rich soils (e.g. top layers of forest soils), pathogen survival is less than 18 months.
  • If P. ramorum is present in green waste incorporated in the soil, survival can be much longer (2 years or more).
  • In inert soils (e.g. potting mix), the pathogen can survive multiple years.  However, for all soils, areas with less temperate climates (cold winters, hot summers) may hasten loss of pathogen viability.

From a practical perspective, if infested forest soil is picked up on tires or shoes from late winter to early summer, the pathogen will likely remain viable for about 1 year, in the absence of incorporated green waste. If soil is picked up from late summer to early fall, survival duration is much less, possibly in the order of a few months.

Does glyphosate (Roundup and other trade names) enhance P. ramorum (sudden oak death) infection?

There is no research or other observational evidence to indicate that glyphosate application increases Phytophthora ramorum infection. In mixed-evergreen and redwood forests some land managers use glyphosate to control invasive weeds, such as French broom, poison oak, and other problematic weeds. In coastal CA, these forest types contain coast live oak, California bay laurel, tanoak, and other plants susceptible to P. ramorum, but the disease is not known to spread or intensify due to glyphosate treatment.

Precautions. Always follow pesticide label instructions and consider non-pesticide alternatives to control pests. Pesticides can be injurious to humans, domestic animals, desirable plants, fish, and other wildlife if they are not handled or applied properly. Use all pesticides selectively and carefully. Follow recommended practices for the disposal of surplus pesticides and pesticide containers.

After taking down a P. ramorum-infested bay tree, can the foliage be left onsite to decompose?

Once down, spores from bay foliage will not travel nearly as far as they do in the canopy. The concern on the ground is that infested leaves, while still fresh, could have spores picked up during a wet event from soil splash onto the trunk of the tree. So, spread bay foliage in a thin layer in a sunny area that will promote drying. Be sure to not have foliage near the base of oak or tanoak trunks where soil splash/infection could occur.

SOD: Cleaning Tools & Equipment

Doug Schmidt All Posts
SOD: Cleaning Tools & Equipment

Topic:

Cleaning tools in SOD-infested areas.

Problem:

Can tools become infectious when used on trees infected by SOD? Yes, in particular when dealing with infected foliage, infested soil, and marginally with infected wood. The risk of spreading SOD is higher if soil or infected leaves are present on tires, shoes or tools. Wood is generally, not as infectious

Recommendation:

 Differently from other pathogens which produce invisible microscopic and often sticky spores that can remain viable even on apparently clean tools, the SOD pathogen produces spores that are normally lodged in plant debris, organic matter, and plant or soil residue.

In order to clean your tools, shoes, and vehicle tires you can follow this two-step procedure:tools1
  • Clean all visible organic residue, plant tissue or soil from the tool. A wire or plastic brush is generally effective. Removal of all visible debris will eliminate 99% of all infectious propagules.
  • Washing with a disinfectant that will kill any remaining spores. We have found that 70% ethanol, diluted bleach, and Lysol brand disinfectant are all effective. Lysol, which contains benzalkonium chloride, a powerful and effective antiseptic, is the product we use most often as ethanol tends to be the most expensive of the three, and bleach can cause corrosion of metal tools.

Note: it is important to ensure all parts that came in contact with infected plant material are visibly clean and that no organic matter remains. This is particularly crucial for tools like chainsaws or machinery like chippers. The physical cleaning step  (above) is critical, and can be effective even without washing although the application of a disinfectant may help). Washing first and then cleaning will be ineffective. Always wear safety glasses and protective equipment as recommended by the manufacturer and always follow the manufacturer’s directions, restrictions, and precautions on the product label.

Research behind the Recommendation:

To test the effectiveness of tool cleaning on the transmission of P. ramorum, a chainsaw and handsaws were “contaminated” with SOD-infected wood chips and saw dust. The saws were treated by different methods in an attempt to “decontaminate” them including, removing the visible organic matter with a wire brush or brushing followed by a disinfectant rinse. The disinfectants used were 10% ethanol, 5% bleach, and lysol (diluted as instructed on the label).

After cleaning, the saws were examined under magnification, any remaining bits of plant or organic matter plated on selective agar Petri dishes. The percentage of infectious propagules that grew on the agar plates is graphed below. Click to rebigulate the pdf.

Download (PDF, 17KB)

Links and References:

Disclaimer: Mention of any company, trade name, or commercial product does not constitute endorsement by the University of California or recommendation for use. Always follow the manufacturer’s directions, restrictions, and precautions on the product label.