National pesticide risk reduction strategy for wireworm in potato

For inquiries please contact:
Pesticide Risk Reduction Program, Pest Management Centre, Agriculture and Agri-Food Canada
pmc.cla.info@agr.gc.ca

April 2015

Preface

Pesticide risk reduction strategies are developed under the Pesticide Risk Reduction Program(PRRP), a joint program of Agriculture and Agri-Food Canada (AAFC) and the Pest Management Regulatory Agency(PMRA) of Health Canada. The Program's objective is to reduce risks to the environment and to human health from pesticide use in agriculture. To achieve this, the Program works with grower groups, provincial experts and researchers to identify gaps in pest management and opportunities for pesticide risk reduction, and to develop and implement strategies to address these.

A pesticide risk reduction strategy is a detailed plan that aims to address grower needs for reduced-risk management tools and practices for specific pest issues. The strategies are developed through extensive consultation with stakeholders. The strategy document presented here summarizes the framework and activities supported by the PRRP. It is intended to provide information about the development and implementation of the strategy and new tools and practices made available through this process.

For more information, please visit the Pest Management Centre.

Acknowledgement

The Pesticide Risk Reduction Program acknowledges all participating stakeholders and organizations, especially, those who contributed to the development of the strategy through the Wireworm Working Group, including: grower organizations, industry processing groups, provincial crop specialists and AAFC researchers.

Executive summary

This document reports on the Pesticide Risk Reduction Program's (PRRP) joint collaborative pesticide risk reduction strategy for the control of wireworm in potatoes. Wireworm was identified as one of the top priorities for potato growers through the PRRP's consultations with stakeholders across Canada, including the Canadian Horticultural Council's Potato Committee.

Traditionally wireworms were controlled using carbamate and organophosphate insecticides; however due to regulatory re-evaluation, the majority of these products have been removed from registration for this use. Phorate was the last organophosphate available for wireworm when it entered a period of regulatory phase-out in 2004 due to a science based assessment of environmental risk to birds, mammals and aquatic organisms. As an economically important crop in Canada, potato was identified as a key priority for strategy development as no suitable alternatives for the control of wireworm were available for this crop.

Knowledge gaps, potential risk reduction solutions and barriers to the adoption of future reduced risk management approaches were identified and developed into a strategic approach for pesticide risk reduction by the PRRP through consultations with key stakeholders. The resulting strategy centred on the need to find lower risk alternatives which would protect the crop while also being environmentally sustainable.

Since 2003 the PRRP has funded 7 projects, exploring the biology and geographic distribution of the pest, as well as funding research leading to the development of pest management solutions. Key outputs from these projects include:

  • improved pesticide screening protocols
  • a national species distribution map
  • efficacy data leading to the minor use registration of clothianidin, chlorpyrifos and bifenthrin
  • novel blended formulations of conventional insecticides and of a wireworm specific strain of Metarhizium anisopliae
  • new recommendations on the use of brown mustard and buckwheat as rotation options to supress wireworms in potato crops

More details about the solutions resulting from this strategy are provided in Table 2 at the end of this document. Through the Canadian Agri-Science Cluster for Horticulture, work continues to further develop the knowledge and tools generated through this strategy into a comprehensive integrated pest management program.

Pest management and pesticide risk reduction issues

Wireworms are the larval stage of click beetles (family: Elateridae). Wireworms live in the soil where they cause damage by chewing and burrowing into the roots and tubers of many different plants. There are more than 800 species of wireworm worldwide, but only a small number of these are serious agricultural threats that cause economic losses. Approximately 30 species are recognized as pests in Canada, many of which are found in potato fields. Potato is one of the most important horticultural crops in Canada, both in planted area (over 150000 hectares) and farm gate sales ($1.2 billion in 2012).

In Canada, many older, broad-spectrum products historically used for control of wireworm such as carbamates and organopshosphates are no longer available or are being phased out. Wireworms are a serious problem in many regions of the country and there are few effective control options. In 2004 the re-evaluation of the regulatory status of phorate was completed and the decision was made to phase out all uses in Canada. As no commercially acceptable alternatives existed at the time for wireworm control in potato, the Pest Management Regulatory Agency (PMRA) extended the phase-out period for this use only, to allow for transition to alternatives. To assist in this the PMRA continues to coordinate and facilitate the Phorate Transition Strategy Working Groupto promote agricultural practices that will decrease the likelihood of wireworm infestations while also identifying potential alternative and support research to aid the registration of products to replace phorate use in potato.

Strategy development

Working group consultations

An expert working group of industry stakeholders including grower groups, provincial crop specialists, researchers and government scientists was established by the PRRP in 2006 to work on the development of a pesticide risk reduction strategy. The group outlined issues, potential solutions and action items which informed the development of the strategy and the framework for program support targeting the issues.

Priority issues and gaps

The pest management issues facing potato growers identified by the working group included:

Lack of knowledge on the distribution of species of concern in Canada

There are many different species of wireworm across Canada, including invasive species from other countries. At the beginning of the strategy there was very limited knowledge on what species of wireworm were present and causing damage in different geographic regions of Canada. The lifecycle of different species was known to vary, with some surviving in different layers of the soil for years at a time. In addition, differences in the susceptibility to chemical and cultural control measures of different species was observed, making targeted testing of potential alternatives a necessity.

Lack of effective control products following phase-out of phorate

With the only available effective control – phorate - under phase-out, the need to screen for potential replacement products was a main priority established by the working group. Identification of effective products was challenging, as knowledge of the actual toxic, lethal and non-lethal effects of different chemical classes on wireworm species were not known. In addition the efficacy of new, more specific insecticide chemistries varied on different species of wireworm.

While biopesticides were being explored for this use, as of the early 2000's they were many years away from being commercially available to growers.

Lack of tools for an effective integrated pest management program

Basic tools such as monitoring and sampling techniques, as well as knowledge pertaining to the effects of cultural controls like crop rotation were insufficiently developed. The vast number of associated variables (bait used, presence of wireworm in different soil layers, soil moisture levels et cetera) complicated the development of sampling techniques in the field.

Some evidence suggested potential in lethal trap crop strategies and green manures; however the impact of alternative rotational crops was not well understood. More knowledge of the potential of rotational crops to reduce populations or oviposition in potato fields was identified as an area needing a thorough literature review and more research.

Need for grower education on wireworm biology and alternative control strategies

Demonstration plots showing IPM (Integrated Pest Management) programs in addition to posters or other educational aids on wireworm biology and IPM components would be required for uptake of any developed approaches.

Action Plan

Based on the information collected through the potato wireworm working group and consultations with stakeholders from other commodities, a pesticide risk reduction strategy, including an action plan for the control of wireworm in agriculture, was developed. The following action plan table outlines the goals of the strategy, identifies targets and milestones, and indicates the activities that took place as part of the strategy.

Three key goals were identified in this strategy to address the above four priority areas:

  • Replacement of organophosphate insecticides with reduced risk products
  • Development and implementation of alternative control strategies
  • Communication of results

Table 1 – Progress and results on action plan to implement a reduced-risk strategy for wireworm management in potato production in Canada

Goal 1. Replacement of organophosphate insecticides with reduced risk products
Target Milestones Status Implementation Activities Completion period
Status legend:
  • Completed: Project addressing a milestone is complete
Laboratory and field procedures to facilitate effective screening of candidate insecticides
  • Develop handling and storage protocols for wireworm
  • Develop a toxicity bioassay to quickly test new insecticides against wireworm
  • Develop a repellency bioassay for use in established protocols
Completed Laboratory and field protocols were developed by Vernon and van Herk through MU03-ENT1. All were used in subsequent projects to identify the mechanism by which potential insecticide classes control wireworm, and these protocols led to new information on lethal, sub lethal and repulsive properties of candidate insecticides. The protocols continue to be used to identify new effective chemistries for control of wireworm. 2003-2006
Registration of alternative chemical insecticides for control of wireworms and click beetles Minor use label expansions submitted and uses added to product labels Completed

Data was generated through both AAFC-PMC programs within projects AAFC04-001, MU03-ENT1 and MUR06-310 for the submissions and registrations below.

  1. Wireworm control

    Chlorpyrifos was registered Canada-wide for control of wireworm in potato, domestic use only, and is only being used in British Columbia. There is no MRL for this product in the United States, and growers supplying table or processed potatoes to United States do not use this product east of British Columbia;

    Clothianidin was registered for suppression of wireworm in potato in 2009. Used with good effect against wireworm species in British Columbia, but not in other provinces;

    Bifenthrin was registered conditionally for control of wireworm in potato as in-furrow spray in May 2014. Will be reviewed for full registration in 2016. No MRL restrictions for trade to United States;

    Thiamethoxam, due to variable efficacy against wireworms in different regions of Canada, has not been pursued for label expansion for use against wireworms by registrant company. It has, however, been registered for use in potatoes as an in-furrow spray and as a seed-piece treatment for systemic control of above-ground pests, and can therefore be used in combination with chlorpyrifos and bifenthrin (non-systemic control of wireworms), which together provide broad-spectrum control of soil and above ground insect pests.

  2. Click beetle control

    Lambda cyhalothrin. Trials conducted in 2014 and 2015 by Vernon and Kabaluk confirmed that foliar applications of lambda cyhalothrin (Matador 120EC) to grass effectively killed adult wireworms (click beetles, Agriotes obscurusand A. lineatus). A data package has been prepared and will be submitted for Minor Use as label expansion for click beetle control on all crops registered for Matador use in 2015. The objective is to kill adults before eggs can be laid in chronically-infested fields, such as in Prince Edward Island.

2003-2014
Development and feasibility assessment of local B.C. isolate of Metarhizium anisopliae Conduct trials and development work to assess potential usefulness of this biocontrol Completed Work conducted through MU03-270 and BPI07-080 indicated that although the M. anisopliae isolate is highly virulent to the larval wireworm stage, observed efficacy may only be appropriate to lower wireworm population levels or as part of an IPM program. However, through later work funded by the Canadian Agri-Science Cluster for Horticulture it was determined that the strain is very effective in the field on adult click beetles and work is continuing under the Canadian Agri-Science Cluster for Horticulture 2. In addition future work will test a promising new formulation of the British Columbia isolate with increased efficacy for the larval wireworm stage. 2003-2010
Determine potential of CA-1 BioGreen for wireworm management in potato and carrot Conduct trials to assess the potential for this product as a reduced risk control for wireworm in carrot and potato Completed Work was conducted through BPI07-200 on a biopesticide derived from mustard (CA-1 BioGreen) for use in potato and carrot. Results indicated product was not effective against wireworms and was phytotoxic to carrots. 2007-2008

Goal 2. Development and implementation of alternative control strategies
Target Milestones Status Implementation Activities Completion period
Status legend:
  • Completed: Project addressing a milestone is complete
Identification of wireworm species of economic importance in different regions Review of available information on wireworm species distribution Completed A short literature review conducted by AAFC Research branch scientists, concluded that more detailed information was required. Not PRRP funded
Develop in-ground bait traps to be used to monitor wireworm Completed Work was initially conducted by AAFC Research Branch scientists. The development of bait traps continued with funding from the Canadian Agri-Science Cluster for Horticulture. Not PRRP funded
Conduct survey of wireworm species distribution in Canada and which species are causing economic damage Completed Original survey was conducted through MUR07-040, and surveys have continued through AgriCluster funding I and II and partnerships with Syngenta, Bayer, and various provincial governments. 2007-2014
Beneficial crop rotations identified Research and selection of appropriate rotational crops Completed Through PRR07-030 both brown mustard and buckwheat were found to significantly reduce resident wireworm populations in Prince Edward Island potato fields when used as an alternative crop rotation to cereals. Further work on this cultural control option was continued through Canadian Agri-Science Cluster for Horticulture and implementation on grower fields began in 2014. 2007-2010
Novel blended reduced risk insecticide formulations Insecticides chosen based on control mechanism; potential blends tested Completed Work was conducted in two projects: MUR06-310 and MUR07-040. Combined in furrow spray [with organophosphate (chlorpyrifos) or pyrethroid (bifenthrin)] with an in-furrow spray or potato seed piece treatment (with a neonicotinoid) provided wireworm control equivalent to phorate with the benefit of reduced impact on beneficial organisms. Combinations of clothianidin and bifenthrin have also shown that the amounts of both insecticides can be reduced while retaining overall efficacy in all provinces tested. These combinations are currently being used by growers in British Columbia and Prince Edward Island. 2006-2010
Attract and kill (A&T) technology developed A&T technology developed Completed Work was conducted through: MUR06-310 and MUR07-040. An attract-and-kill (A&K) method was developed whereby wheat seed treated with fipronil and thiamethoxam can be planted in-furrow alongside potato seed. The A&K wheat rapidly attracts wireworms to their death, resulting in tuber blemishes being reduced to the same level as seen with phorate, but with much higher levels of wireworm kill. This is the first example of a highly effective living A&K intercropping method for control of wireworms. Although fipronil is not registered in Canada, the same method may be appropriate with other actives. These studies are continuing under the Canadian Agri-Science Cluster for Horticulture I and II. 2006-2010

Goal 3. Communication of results
Target Milestones Status Implementation Activities Completion period
Status legend:
  • Completed: Project addressing a milestone is complete
Improved grower knowledge and adoption of newly introduced tools and methods Dissemination of strategy accomplishments to the public Completed

Transfer of knowledge resulting from this strategy was accomplished through the distribution of the PRRP factsheet Reduced-risk Wireworm Management in Potato.

The first version of National Wireworm Species Distribution Map (from MUR07-040) is available on the PRRP website.

2010
Communicate project results to industry and grower organizations to inform national decisions in wireworm in potato management. Completed Project results were regularly communicated to representatives through reports, presentations and attendance at grower and industry meetings. Informing industry decision makers of strategy outcomes contributed to successful application by industry for on-going support for wireworm work under the Canadian Agri-Science Cluster for Horticulture 2010

Strategy outcomes

  • Identification of different wireworm species prevalent in key regions in Canada informing the development of targeted management strategies.
  • New knowledge on the effects of different classes of insecticides on wireworms leading to the development of new reduced risk blends and innovative attract and kill strategies.
  • Three new products available in different chemistry classes, providing alternative controls while also decreasing the development of resistance.
  • Identification of a wireworm specific biocontrol strain of Metarhizum anisopliaewhich is leading to the development of a new biopesticide.
  • New knowledge on the use of rotational crops as part of a reduced risk approach for wireworm management in Prince Edward Island.

Strategy impact: then and now

In 2003 Canadian potato growers were facing the phase out of phorate by 2006 with no alternative solutions, either chemical, biopesticide or cultural for wireworm control. Identification and implementation of acceptable alternatives proved to be a challenge due to a number of factors including: complex biology and behavior of the pest, regional variability of species, varying susceptibility of different species to control measures and complications in the registration of new insecticides. As a result the phase-out date for phorate has been extended to 2015.

The strategy was successful in generating important new knowledge and preliminary tools that have laid the groundwork for the continuing development of innovative, reduced risk solutions (Table 2). Work is being continued today in the areas of: harmonized chemical efficacy studies; development and implementation of attract and kill strategies and reduced risk insecticidal blends; national surveys on wireworm populations; crop rotation, and; the development of a Metarhizium biopesticide for wireworms and adult click beetles. Further funding to support this work was obtained through the industry-led federal funding program, the Canadian Agri-Science Cluster for Horticulture 2.

Table 2. Potential impacts of control solutions developed through the wireworm strategy
Solution Pesticide risk reduction mechanism Provinces where technology is applicable Total crop acreage (hectare) Potential acreage for adoption (in percent) Additional benefits and comments
Map of wireworm distribution in Canada Targeted, knowledge based management practices developed, and increased likelihood of risk tools being recommended and adopted All potato producing provinces 140,000 100 Survey continues to 2015. The knowledge gained from this work is crucial in developing targeted approaches given the response of different species of wireworm to chemical and cultural controls.
Unique laboratory and field protocols for screening of wireworm control products Increased likelihood of reduced risk tools being identified and recommended All potato producing provinces 140,000 100 These protocols are now used to efficiently and cost-effectively identify candidate insecticides for use against wireworm and have played an important role in the past 10 years in screening options.
A strain of Metarhizium anisopliaefor wireworm control Reduction in chemical pesticide use British Columbia 2,400 2 Isolate is effective for the larval and adult stage. Work is continuing to test a new formulation of this isolate with demonstrated high efficacy in the field.
3 new control products (chlorpyrifos, clothianidin and bifenthrin) Reduction in pest pressure All potato producing provinces 140,000 100 When applied on their own the products registered from this work do not have comparable control to phorate, however blends of these active ingredients provide equivalent blemish control and are now being used in British Columbia and Prince Edward Island
Brown mustard and buckwheat as rotational crops to reduce wireworm populations Reduction in pest pressure Prince Edward Island 36,500 26 Brown mustard as a rotation crop was implemented on commercial fields in Prince Edward Island in 2014.Crop rotation research is continuing in this province, future work may examine applicability in other provinces.

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