NRC Accepts Preliminary Hazardous Substances Report on Pesticide Use on Public Property


The Initial Report Recommends an Immediate Ban on Neonicotinoid Use by the City, a Phaseout of Glyphosate Use, and Gradual Conversion of Parks and Open Spaces to more Green and/or Organic Status.

by Alan Pryor

This article is timely given the recent incident regarding a controversial pesticide application recently at Slide Hill Park as reported yesterday by Paul Steinberg yesterday in the Vanguard (An Apparent and Sneaky About-Face on Neighborhood Efforts to Care for Parks).

At its January 23rd meeting, the NRC’s Hazardous Substances Subcommittee presented a report to the NRC for discussion purposes that proposed sweeping changes to the City of Davis’ current Integrated Pest Management (IPM)/Pesticide Use Policy. After further discussion on February 27, the NRC unanimously accepted the report with its policy recommendations and proposed next steps. Other Commissions including Open Space & Habitat and Recreation & Parks are currently deliberating the proposed changes and Staff has yet to respond.

The report is entitled “Discussion Paper: Pesticide Use by the City of Davis with Initial Recommendations to Reduce Use In Public Places and Potential for Exposure and to Increase Efficiency”. The report can be downloaded in its entirety at

Disclosure by Author – I am a member of both the NRC and their Hazardous Substances Subcommittee that authored the report. I am a past Certified Pest Adviser (CPA) and have been managing a family-owned Certified Organic almond orchard for 30 years. I am also a past Visiting Scientist at the Department of Nematology at UCD where I investigated environmentally-benign pesticide alternatives.

Note by Author: I understand this article will be published on Thursday, March 2 and I suspect it will generate a few comments and inquiries to which a technical response may be warranted. I will be unavailable to provide such responses until later in the day on Thursday but will endeavor to do so as soon as possible.

Following is the Executive Summary and Table of Contents of the Report as accepted by the NRC.


Introduction and Background

Davis established its first IPM program in 1989 and its first IPM coordinator was hired in 1990. Since 2007, consistent progress has been made by the current IPM Sin reducing use of pesticides in public places across Davis and in reaching out to the local community to teach IPM principles. In particular, steady reduction of overall use and/or elimination of some of the most toxic and or environmentally persistent chemicals has been seen such as glyphosate (a herbicide found in Round-Up TM) and neonicotinoids (a class of systemic insecticide implicated in pollinator die-off).

Within the last year, there have been of citizen complaints and observations about inappropriate use or planned use of pesticides in locations used by children and pets throughout the City where they had previously not been used. These included herbicide spraying or planned spraying in established Pesticide Hazard and Exposure Reduction Zones in certain major parks (Mace Ranch and Slide Hill), directly adjacent to childrens’ or pet animals’ play areas in other parks in South Davis, along a storm drainage channels adjacent to a walking path in North Davis, and in the North Davis ditch open space areas, and green belts in South Davis and North Davis.

An update of pesticide use in the City also shows increased overall glyphosate use as a herbicide in the City as well as a renewed use of neonicotinoids by City Staff replacing an unwritten policy of discontinuance of neonicotinoid . As a result, three different City Commissions discussed the problem and passed a series of motions calling on the City Council to establish a new body comprising representatives of the Natural Resources, Open Space and Habitat, and Recreation and Parks Commissions. The task of the new body would be to undertake a comprehensive pesticide use review in Davis with additional stated objectives of eliminating use of the neonicotinoid class of insecticide as soon as possible due to their adverse effects on pollinators. It was also recommended that the City gradually phase out the use of glyphosate as a herbicide in the City due to recent disclosures of environmental toxicity.

Eventually, it was unilaterally decided by Staff that such a review of the IPM and Pesticide Use policy would alternatively be undertaken by the Hazardous Material Subcommittee of the Natural Resources Commission with subsequent review by all three of the Commissions. This report is the initial effort by this subcommittee to identify and quantify the problems and make specific recommendations to improve the IPM program in Davis.

Scope of Problem

The City of Davis currently manages 1,616 acres of land that may be subject to pesticide application by the city. This acreage is divided into six major management areas including:

The Public Works Department is by far the largest user of pesticides in the City accounting for approximately 80% of the glyphosate used annually and almost 100% of the herbicides Garlon, Transline, and Telar. Much of this use is associated with the overland flow process at the wastewater treatment plant and associated vegetation management requirements will be eliminated upon completion of the wastewater treatment plant upgrades. In general, the public is not exposed to these applications although there is substantial environmental exposure associated with this use. A substantial amount of herbicide is also used for storm water conveyance channels although most of this weed control can also be accomplished by mowing. Most storm channels are freely accessible by the public and often used by children “exploring” and/or pets during roaming activities

Parks and green belts are the next largest user of herbicides and represent the most common mode of exposure to the general public. Most of the alternative treatments discussed below and in Section 4 of this report have been carried out to some degree to reduce herbicide use in these areas. These herbicides are applied both by City workers and the contracted landscape maintenance firm with that firm using approximately twice as much herbicide as City workers. It is recommended that initial efforts to reduce public exposure to these herbicides should focus on application to parks and greenbelts.

Proven Non-Toxic Alternatives Exist to Eliminate Use of the Most Toxic Pesticides Used by the City – Glyphosate for Weed Control and Neonicotinoids to kill Tree Aphids and Lawn Grubs

Alternatives to Glyphosate for Weed Control

The overwhelming use of pesticides in Davis is for weed control. However, there are a variety of proven alternative methods available for acceptable weed control in lieu of use of glyphosate or other contact or pre-emergent herbicides. These include:

  • Mechanical Removal (Weeding),
  • Mulching,
  • Solarization,
  • Grazing,
  • Weed Flaming,
  • Green Herbicides,
  • Use of Native Vegetation in Landscaping Projects, and
  • Irrigation Control

Alternatives to Neonicotinoids for Tree Aphid and Turf Grub Control

The City has also reintroduced use of a neonicotinoid insecticide (“Imidicloprid”) for treatment of leaf-sucking aphids on some trees (particularly Chinese Hackberry). Such an aphid infestation can result in deposition of “honeydew” excretions which fall to the ground and are unsightly. Staff has stated this presents a potential public safety hazard on concrete surfaces which view in not necessarily shared by the subcommittee.

In lieu of conventional treatments with systemic insecticides (typically neonicotinoids), good control of the problem can be obtained by maintaining tree health and vigor of the tree through proper watering and fertilization, application of a dormant spray during the winter months to smother overwintering eggs (organic copper-oil formulations are available), and release of predatory lace-wings which feed on the aphids in the spring and/or summer if warranted by monitoring.

Grubs live and propagate beneath lawn surfaces by feeding on the grass roots which can cause death or unsightly browning of the overlying turf. Staff has stated such turf damage can result in uneven playing surfaces and possible trip hazards on recreation fields which view in not necessarily shared by the subcommittee. Often neonicotinoids are applied to the turf surface which is uptaken by the grass and results in death of the feeding grubs. Good control can otherwise be obtained by biological release of appropriate nematodes populations which are eaten only by the grubs and results in their near-immediate death, or by application of non-systemic, contact insecticides.

Other Municipal IPM Strategies

Many U.S. cities, particularly in the western half of the country, have adopted or implemented IPM programs and policies. To various degrees, these mandate use of or consideration of use of cultural mechanisms or organic or least toxic chemicals on public property in lieu of chemicals with more adverse environmental impacts or persistence of health and safety issue.

Following are lists of such California cities:

  • Policies or ordinances restricting use of toxic pesticides on public property in favor of alternative, organic methods – San Francisco, Richmond, Fairfax, Irvine
  • Policies or ordinances promoting an IPM policy that restricts highly toxic pesticides and urges pesticide use as a last resort – Moraga, Oakland, San Anselmo, Corte Madera, Mill Valley,
  • Policies or ordinances promoting an IPM policy that urges pesticide use as a last resort – Palo Alto, Berkeley, Albany, Arcata
  • Policies or ordinances encourages implementation of a limited IPM programDavis, Contra Costa Co, Alameda Co, Marin Co., Santa Barbara

Following are lists of Western US cities that have Park policies that prohibit pesticide usage in parks:

  • Policies or ordinances prohibiting the use of non-organic pesticides in public parks with limited exceptions – San Carlos CA, Portland OR, Eugene OR, King Co. WA, Seattle WA, Shoreline, WA

Following are lists of Western US cities that have policies that prohibit the use of neonicotinoid insecticides on public property with limited exceptions:

  • Policies or ordinances prohibiting the use of neonicotinoid insecticides in public places with limited exceptions – Sac, Boulder and Boulder County CO, Seattle WA, Spokane WA, Thurston County WA, Milwaukie OR


On December 7th0 – 90 members of the public attended in addition to speakers, City Staff, and members of various City citizen commissions. An extended Q&A and public comments period was also held in which many members of the public spoke in favor of reduced pesticide use by the City.

This sentiment was also expressed by many of the 25 participants in a survey conducted by the sub-committee both on and distributed and collected after the public forum. The survey results show that the survey participants are quite knowledgeable about IPM, glyphosate and neonicotinoids, and how tolerant they might be of seasonal or periodic “unconventional” or unkempt look that is natural in transitioning from using chemicals to more Green or organic practices.

Survey Results Summary:

  1. 100% are familiar with the impacts of pesticides on pollinators.
  2. 92% of respondents make an effort to reduce pesticides at home.
  3. 91% said they are willing to put in at least 1-2 hours per month to volunteer to help maintain those parks by pulling weeds or spreading mulch.

These results indicate a strong desire on the part of the survey participants to elimof pesticides and a willingness to tolerate some seasonal messy appearance to accomplish long term Green IPM goals (there were no responses that indicated a desire for manicured landscapes in parks or greenbelts). And they indicated they were willing to volunteer their time to make it happen in their parks.

Proposed Policy Changes to Further Explore

  1. Move IPM Specialist from Parks and Community Services Department to the Environmental Resources Division within Public Works, or to the Open Space Division within Community Development with Supervisory Authority over Pesticide Management Citywide
  2. Immediately Ban Use of Neonicotinoids
  3. Gradual phaseoutof glyphosate on all public places and open spaces over a three year period
  4. Convert all parks and open spaces where children and pets play to “Green” status and strive for full organic status with neighborhood volunteers for problematic weed abatement
  5. Concurrent public education plan, activities, and signage to notify residents
  6. Establish City-wide abatement crew under the IPM Specialist
  7. Update the IPM Policy to be more specific regarding exemption procedures
  8. Incorporate IPM policy requirements into city contracts/lease agreements and establish practices
  9. Increase Public Availability of IPM and Pesticide Application Data

Proposed Next Steps

  1. Present this report to the Natural Resources, Open Space and Habitat, and Recreation and Parks Commission – Upon acceptance of this report following initial presentation to and receipt of comments from the Natural Resources Commission, it should be subsequently presented to Staff and the Open Space and Habitat Commission and the Parks and Recreation Commission by the Hazardous Material subcommittee comments and deliberation.
  1. Prepare Detailed Time-line and Financial Analysis for Each Goal – Upon receipt of comments from the respective Commissions and following further discussions with Staff, an implementation time-line should be developed including a cost analysis for implementing each objective or goal in the Plan
  1. Plan for Additional Public Outreach and Input – Staff has indicated their intention to perform further public outreach including a public forum to discuss standards of service and an additional public survey with a broader reach. The Hazardous Material Subcommittee welcomes these efforts providing they are coordinated with an include input from the respective Commission.
  1. Update Initial Report with Finalized Recommendations and Additional Information and Present Policy Changes to City Council – Upon receiving comments from each of the Commissions, suggestions from Staff, and input from the public outreach effort, the initial report will be updated and finalized and presented to City Council for their deliberations.

About The Author

Disclaimer: the views expressed by guest writers are strictly those of the author and may not reflect the views of the Vanguard, its editor, or its editorial board.

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11 thoughts on “NRC Accepts Preliminary Hazardous Substances Report on Pesticide Use on Public Property”

  1. Don Shor

    Here is the city’s pesticide use report for 2016.

    If I’m reading this correctly, the city has used about three gallons of glyphosate city-wide, and less than one pint of imidacloprid.

    A couple of important points.

    Neither of these pesticides, particularly at these rates of application, poses any health risk to the public.

    Non-chemical approaches to the Asian woolly hackberry aphid aren’t very effective. It requires constant washing of surfaces to make a play site usable. Ultimately the best bet for the single situation where they appear to be treating a tree will be to remove the tree and replace it with another species.

    Having said all of that, the public doesn’t like to see pesticides being used and there is a strongly held opinion among many that none should be used. There is a strong preference for organic material usage. It should be noted that those organic materials aren’t actually any safer than the conventional materials, and people will still object to seeing them used. So non-chemical methods will be preferred by those pressing for this policy change.

    These are philosophical arguments, and there isn’t much point in debating the science on this issue. In my opinion (I have had certification and do have experience on this topic) the non-chemical strategies can work almost as well as the chemical approaches if they are implemented consistently. It will take more labor, but volunteer labor can eliminate any cost increase to the city.

    It appears that pesticide usage by the city has increased somewhat recently. It would be worth asking why and what alternatives could be adopted. There may be some intractable perennial weeds in some situations that are being dealt with. It could well be that enhancing the oversight status of the IPM specialist could temper that trend. I think some inquiries by council members to staff would answer those questions.

    1. Paul Steinberg


      With respect to your comments above:

      1. I strongly disagree with your initial sentence – that these post no risk to the public.  Its widely documented and studied on a global basis that glyphosate is a poison affecting animals and plants alike. I don’t wish to debate that here. The World Health Organization has published an article linking it to cancer – see and it is banned for use in a number of countries citing environmental and health issues.

      2. I am not sure if you’re reading the amounts used accurately or not, given the number of times these have been applied across Davis as reported, I find it hard to reconcile that the number as you interpret it is as “low” as you state.  I’ll leave that to others to clarify.

      3.  The thrust of my article published yesterday, and in recognition and support of our efforts last year, is that we do not need to use chemicals, conventional Monsanto-created poisons or otherwise.  These plants we seek to remove can be in other ways, manually for sure. There are many benefits to doing so and really no drawbacks.

      4. Comparative costs of poison vs. manual:  I’d be VERY interested to see what the real cost of chemical/poison application is.  Other than the direct cost of the chemical (and probably a longer term contract to procure these at a fixed rate), there are the costs of: training the applicators, suiting them up, disposal of the materials and applicators, costs associated with notifying neighborhoods; monitoring and responding to inquiries and complaints; insurance costs associated with staff working with chemicals…. There may be other costs I am not aware of.

      How these costs compare with the cost of physical labor + neighborhood volunteers… that would be interesting if cost is the city’s main argument.

      Perhaps Alan Pryor can weigh in on this above.

      1. Don Shor

        I am not sure if you’re reading the amounts used accurately or not, given the number of times these have been applied across Davis as reported, I find it hard to reconcile that the number as you interpret it is as “low” as you state. I’ll leave that to others to clarify.

        I believe they are required to report all usage, so I’ll assume these numbers are correct. It doesn’t take much active ingredient of glyphosate to work, especially when it’s used with Scythe. That’s one of the reasons they’re using the Scythe.
        It would be hard to quantify those ongoing costs you’ve mentioned.
        As to the WHO, regulatory agencies have not accepted the conclusions of the IARP report (that’s the agency that does the work for the WHO). The European Food Safety Authority and, apparently, the EPA have not agreed with the conclusions. It’s a subject some might find interesting, but not really germane here. I think a large percentage of Davis residents would like the parks to be maintained without pesticides (organic or otherwise). Some might add “to the greatest extent possible” while others would say “at all.” And it is possible to do it, particularly if citizens are willing to donate labor.

        For those who are interested, here’s the EFSA assessment:

        The peer review group concluded that glyphosate is unlikely to be genotoxic (i.e. damaging to DNA) or to pose a carcinogenic threat to humans. Glyphosate is not proposed to be classified as carcinogenic under the EU regulation for classification, labelling and packaging of chemical substances. In particular, all the Member State experts but one agreed that neither the epidemiological data (i.e. on humans) nor the evidence from animal studies demonstrated causality between exposure to glyphosate and the development of cancer in humans.

        1. Don Shor

          Note: the concern about imidacloprid (on the hackberry near the playground) is the impact on pollinators, not toxicity. Separate issue from glyphosate. Just for those who don’t feel like reading through the committee report. It’s used because of the Asian woolly hackberry aphid, which excretes honeydew that drips all over everything underneath the tree all summer long. The honeydew needs to be washed off daily or the site becomes pretty unusable.

          1. Don Shor

            I’m sure they only report active ingredient. So if you’re using 2.67 oz. of glyphosate per gallon (makes a 2% strength) they report 2.67 oz. One could extrapolate about the total gallons of solution sprayed. The Scythe allows them to use less glyphosate, probably a 1% solution mixed with the Scythe. I was surprised by how little glyphosate is used, frankly. That’s a result of the IPM adviser recommending the other materials, I’d guess. So giving the IPM adviser more oversight would probably help to continue that trend.

        2. Alan Pryor

          Re: Glyphosate and Neonicotinoid Toxicity – Readers can get extensively referenced information on the toxicity and/or environmental impacts of both glyphosate and neonicotinoids by downloading the full NRC report at the URL given at the beginning of this article. The information is contained in Appendices A and B of the report. The current understanding of the potential carcinogenicity of glyphosate is especially controversial and extensively discussed in the report.

          Re: Alternatives to Neonicotinoids for Aphid Infestations on Hackberry Trees – I have personally had very good success with controlling aphids on Hackberry Trees by spraying a dormant spray of Copper and tree oil (both are available in organically-approved formulations) for over-wintering insect eggs and scales followed up by monitoring and release of predatory Lacewings in the spring if warranted. If a problem still persists, I hose off the tree (using the run-off water to also irrigate the tree during the dry summer) but have never had to do it more than once or twice a summer and never approaching daily washings as Don suggests.

          1. Don Shor

            Copper is an approved fungicide for organic agriculture and landscape uses. But I would not recommend it in this case, since the pest is an insect. Copper wouldn’t affect the aphid population. The oil would be intended for killing the overwintering stage of the insect, or it can be used at a lower rate during the growing season for adult aphid control. Oil sprays are reasonably effective, though they do leave a sticky/tacky residue and multiple applications would probably be necessary. Spraying the trees is a challenge and is likely to spark resistance because the applicators would be wearing full protective gear.
            Since the Asian woolly hackberry aphid arrived in 2002, infestation rates have ranged quite a bit. At first it was severe and areas immediately beneath trees were just plain unusable — people were ready to remove the trees. Hence the use of the systemic.
            In some cases, natural control has gradually increased to the point that it is not such a nuisance. I would not promise that to anyone who counts on a particular playground for frequent use, but it is possible. Honestly, in the long run it’s probably best to just relocate the play structures or replace the tree if this is going to be a source of controversy. The population ebbs and flows and some years will be stickier than others. People with young kids won’t like the nuisance of it.
            I doubt that releasing predatory insects would be cost-effective for the city, but it would be something homeowners could certainly do by pooling funds. Alan Pryor or I can provide sources for mail-ordering the beneficials if people are interested.

  2. Paul Steinberg

    Don, thanks for your detailed replies – regardless of my (or others) viewpoint on these.  Your comment I find most appropriate … the desire of many to just avoid use of chemicals at all being the ideal… But it takes commitment, takes work and takes participation by the community. (and then there is that sneaky aspect of it… why those in charge push ahead with chemical application in spite of significant local opposition…

    1. Howard P

      Two questions… how do you define “chemicals” and “significant”?  Meant as a slightly baited question…  H2O is a chemical… toxic to the point of death in large quantities of exposure/ingestion…

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