Regular monitoring is recommended to ensure infestations are managed early and before trees become hazardous. Early detection enables the treatment of trees when they are lightly infested ensuring the greatest chance of overcoming infestations.
Monitoring and Sampling Best Practices Video
A video outlining best practices in monitoring and sampling for invasive shothole borers (ISHB) is now available on the University of California Integrated Pest Management YouTube channel. View it at https://youtu.be/1LKKJe3NgTY
Cultural and Chemical Management
Management decisions for trees in the urban forest depend on whether or not the tree species is a reproductive host, the level of infestation, tree location, and the potential hazards associated with infested limbs and trunks. Use the ISHB Detection & Management Assessment Tool to help you determine the best steps to manage ISHB-FD infestations.
For low to moderately infested trees, the removal of actively infested branches as well as chemical treatments with a combination of insecticide and fungicide have proven to be effective control measures. Treatment options include systemic pesticides that can be applied as a tree injection or soil drench and pesticide bark sprays. These treatments are ideally timed in early spring and fall when adult beetles are emerging.
Heavily infested trees (with more than 150 entry/exit holes and signs of branch dieback) often have their vascular system extremely compromised by the disease and may not be able to be saved with chemical treatments. These trees are a big source of new beetles and often become hazardous due to the structural damage caused by the beetles’ galleries. Timely removal and proper disposal of the infested wood is recommended in these cases.
So far, no preventative treatment has been proven effective. Treatment of uninfested trees is not recommended.
A certified arborist should be familiar with best practices with respect to both maintaining trees and disposing of infested wood and green waste. Find a Certified Arborist
- Don't move firewood!
Many wood-boring pests, including ISHB, are spread by the transport of infested wood. Buy firewood where you intend to burn it. Visit dontmovefirewood.org and www.firewood.ca.gov for additional resources and information that you can share with others.
Properly dispose of infested material
Do not use untreated ISHB-infested logs or chips for firewood or mulch. Options for treating infested material include solarization, composting, kiln-drying, and biogeneration. Learn more about these options here.
Disinfect pruning tools
Poor pruning practices can facilitate the spread of plant disease. Any pruning, sampling, or other tools that come into contact with infected wood should be sanitized before being used on uninfected trees. This includes chainsaws and wood chipping equipment. If several infested and uninfested trees need to be maintained on a property, we recommend managing the trees in batches. First take care of all of the uninfested trees, then move to the infested trees so that your tools won't need to be cleaned until the end of the day.
For pruning and tool sterilization tips, see UC Riverside's "Best Management Practices for Disease in Oak Woodlands" .
Wood from ISHB-infested trunks and branches is still full of live beetles. If infested wood is not properly handled, beetles will emerge from the cut logs and attack new hosts. This two-step process will help prevent the beetles from spreading to other locations or re-infesting your own property. Details on each procedure can be found below.
Chip infested wood immediately after tree removal or pruning. Running ISHB-infested material through a wood chipper is one of the most effective ways to kill the vast majority of beetles living in cut logs.
- Chip as small as possible. The chip size should be smaller than 3 inches. Chipping to 1 inch or less is optimal.
- Do not leave piles of contaminated wood uncovered. If wood cannot be chipped immediately, tightly wrap the logs in plastic to contain the beetles.
- Cover unchipped wood in transport.
- If wood cannot be chipped, tightly cover cut logs and follow directions for solarization or kiln-drying.
After chipping infested wood, select one of the options below to ensure that beetles and fungi are destroyed. Some of these methods also work for logs that cannot be chipped.
Always cover the material in transit when transporting infested plant material to another site for treatment.
This method is suitable for handling both infested chips and logs. When done correctly, solar energy will heat plant material until both the beetle and fungi are killed.
How long does infested wood need to be solarized?
Solarization is most effective during the peak of summer, when temperatures are higher and days are longer, but it may be used during other seasons as long as time and space can be committed.
- July - August: Cover chips or logs with sturdy plastic for at least 6 weeks. Temperatures during these months should be regularly above 95°F.
- September - June: Cover chips or logs with sturdy plastic for at least 6 months.
Other tips for proper solarization:
- Use a sturdy plastic sheet or tarp that can withstand rain and wind. Clear plastic is preferred since it lets more sunlight through and heats the content more efficiently.
- Fully contain chips, logs, and beetles by wrapping plastic both underneath and over the material.
- Keep log or chip layers as thin as possible, two logs deep maximum, to ensure even heating throughout the pile.
Proper composting should kill remaining beetles and fungi in the chips. Composted, chipped plant material may then be re-purposed as mulch or added back into soil to improve texture and water retention.
It is recommended that wood chips be composted at a professional composting facility that has earned the U.S. Composting Council's Seal of Testing Assurance (STA). Facilities in the STA program are tested for proper decomposition and pathogen control.
Find a local STA Compost Facility at the US Composting Council website.
Composting can also be done at home, as long as guidelines for adequate decomposition are carefully followed. See UC IPM for guidelines on composting. Find additional composting tips from the UCCE Master Gardeners or from CalRecycle.
Unchipped, ISHB-infested wood can be decontaminated by the heat used in kiln-drying. To destroy the beetles and fungi that cause Fusarium dieback, it is necessary to heat the material for at least 60 minutes at 140°F. Wood that has been disinfected can then be re-purposed.
Biogeneration facilities burn green waste and convert it into energy. Learn more about biomass energy here.