The County of Hawai`i, Hawaiian Earth Products and the Hawaii Ant Lab are committed to preventing the spread of Little Fire Ants, Coconut Rhinoceros Beetle, Rapid Ohia Death and other pests or pathogens. This page shows the status of the green-waste processing facilities in Hilo and Waikaloa.
The County of Hawai`i provides free mulch to county residents. This material is a great soil additive, adding valuable organic matter and water retention properties to agricultural and residential soils. It is produced from green waste taken to landfills by other residents in the area. One potential disadvantage of this material is that it may contain plant pests and diseases, including Little Fire Ants, Coconut Rhinoceros Beetles, Rapid Ohia Death and others. The County of Hawai`i, in collaboration with Hawai`i Ant Lab and Hawaiian Earth Products, have established new protocols for it's Hilo and Waikoloa processing sites. These protocols with reduce the presence of these plant pests and diseases to the lowest level practical.
- Tell me about the background to this project
- Waste management in Hawai`i is an expensive exercise and as residents, we all pay for this service. The County of Hawai‘i has committed to a “path to zero waste” which will reduce costs and the need for more landfill sites. One part of that policy is to re-use organic garden or green waste (clippings, cuttings, logs and unpainted pallets) by mulching this material and giving it at no cost to residents for use on gardens and orchards. This keeps around 40,000 tons of green waste out of our landfills each year!
Using mulch on garden beds and around trees has many advantages. It reduces water use, enriches the soil, promotes a healthy micro-environment for beneficial soil organisms that help make nutrients available to plants and suppresses weed growth. Best of all, its free!
An unfortunate side-effect of mulching green material and re-distributing it is the possibility that plant pests and pathogens might be present in the mulch, thereby spreading these problems to other locations. In Hawai‘i, Little Fire Ants are a special concern. No-one wants to accidentally bring these critters to their home! Many households in Hilo and surrounding districts have LFA, so when these households take their garden waste to the one of the County’s green waste facilities, it is inevitable that some LFA will be attached to the clippings and cuttings.
Now, the mulching process is fairly brutal – all the garden waste is fed into a high-powered grinder where it is torn into tiny little chunks. Huge logs can be reduced to match sticks in seconds! Most arthropods (insects, spiders etc) will also be ground up and not survive. But, some insects can survive this process and make their home in the newly formed mulch.
Both the County of Hawai`i and Hawai`i Earth Products are committed to preventing the spread of invasive species. For this reason, they have embarked on a reisk management program to reduce the likelihood of inadvertantly spreading invasive species through the movement of county mulch.
- What is "risk management"?
- The term "risk management" is used in a number of professions to describe a systematic way of assessing and addressing the threat of an adverse event. There are five key steps in a risk management system:
1. identify threats
2. assess the vulnerability of critical assets to specific threats
3. determine the likelihood of the risk and the consequences
4. identify ways to reduce those risks
5. prioritize risk reduction measures based on a strategy
For example, there are many risks when driving an automobile (identify threat). One risk is that you might be injured in an accident (assess vulnerability). We know that automobile accidents happen on a regular basis and the consequences include damage to the car (expensive repair bills), and personal injury (hospitalization). There are many things we can do to reduce these risks: defensive driving, buying a newer car with extra safety features, not driving and wearing a seatbelt. Once we have a list of ways to reduce these risks, we can select the methods we are going to use. Buying a new car might not be possible for example, but always wearing a seatbelt is also effective and does not entail the same costs.
But, even if you take every possible precaution, accidents still happen. So, even if you take all possible actions to reduce your chances of an accident, it is still possible one might happen. But, athe probability of adverse consequences are much less if you wear a seatbelt, have a newer model car and drive safely.
The same process is an effective way of looking at the possibility of getting mulch that is infested with Little Fire Ants. We look at all the possible ways we can reduce the threat of LFA and choose the methods that are practical and possible.
- What is the guarantee?
- There are no absolute guarantees that the mulch you receive will be free of LFA and other pests or diseases. There is always a small chance that somehow, these things somehow slip through the system from time to time. What IS important is that all practical steps have been taken to prevent this from happening, and this reduces the likelihood of an adverse event from happening.
So, how did the County, HEP and HAL go about developing protocols to manage these risks?
First, let's look at the facility in Waikoloa.
1. This site, near the Kona Airport is a moonscape. It's dry, hot, surrounded by a recent lava flow and generally an inhospitable site for Little Fire Ants. LFA prefer warm, moist and shady conditions - exactly the opposite of conditions at this site.
2. Although LFA are found in west Hawaii, they are not widespread in the area. This means that only a few loads of infested material are likely to arrive at this site (compared with Hilo for example).
3. Once processed, the mulch in Waikoloa remains on the site for about a month. During this time the mulch heats up to over 130 degrees and is regularly turned.
These three factors mean that LFA are not likely to survive because the climate and moisture are far from ideal, there is much less material arriving from infested locations, and the heat generated by decomposition are likely to kill any surviving ants. An additional advantage is that the processed mulch remains onsite for around 4-6 weeks. This gives us an opportunity to survey all the mulch piles for LFA before they leave.
HAL has developed a protocol that includes regular monitoring for LFA, diversion of known infested material to another location and maintaining the facility in an ant-free state. Together, these actions will reduce the risks associated with LFA in mulch to a neglible level. Is there an absolute guarantee? - No, but the probability is extremely low.
What about the Hilo site?
Well, unlike the Waikoloa site, it is warm, wet, shaded AND infested with LFA. The neighboring land is also infested which means there is a constant threat of LFA moving into the mulch during all stages of the mulching process. Additionally, because most properties in and around Hilo are already infested, many if not most loads of raw material will arrive already infested with LFA. To make matters even more risky, mulch is often taken from the site within hours of it being shredded. None of these things help.
So, the County and HEP have developed a protocol that includes the following risk minimization activities:
1. Develop and implement a treatment program for the site. This will include the use of baits and residual insecticides applied around the site and between rows of mulch.
2. Keep the mulch on site so it can heat up (over 130 degrees). This should kill any ants and other pests or diseases in the mulch.
3. Regular monitoring on the site to make sure ants are being controlled around and within the site.
The combination of these risk management actions will virtually eliminate invasive ants, other insects and plant diseases from the mulch. Remember, there is always a small possibility that ants occasionally survive this process. If you are concerned about even this small risk, check out the HAL fact sheet for managing mulch.
Results of surveys at Hilo facility. Red circles show where LFA were detected and white circles show where a sample was taken and no LFA found. At our last survey in May 2017, only a single LFA was found on the entire site. Well Done HEP!
download key documents
Little Fire Ants and County mulch page
Results of surveys at the Waikoloa facility. Red circles show where LFA were detected and white circles show where a sample was taken and no LFA found. No LFA have been detected since surveys began in June 2016 site. Well Done HEP!