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Reduced-Risk Strategy for Soil Fumigant Replacement: Ginseng Replant Disease

For inquiries regarding this strategy please contact:
Pest Management Centre, Agriculture and Agri-Food Canada
aafc.pmcinfo-clainfo.aac@canada.ca

March 2018

Preface

Pesticide risk reduction strategies are developed under Pesticide Risk Reduction (PRR) of Agriculture and Agri-Food Canada's (AAFC) Pest Management Centre. To reduce undesirable impact of the use of pesticides in agriculture, PRR works with grower groups, industry, provinces, researchers and regulators to identify gaps in pest management and opportunities to develop and implement strategies to address these.

A pesticide risk reduction strategy is a detailed plan developed through consultations with stakeholders aiming to address grower needs for reduced-risk management tools and practices for a specific pest issues. The strategy document presented herein is intended to update participating stakeholders and the public at large on the activities supported by the PRR in developing and implementing the strategy and the new tools and practices made available through this process.

For more information, please visit the Pest Management Centre.

Acknowledgement

Pesticide Risk Reduction acknowledges the contribution of participating organizations and collaborating stakeholders, including the Ontario Ginseng Growers Association and members of the Ginseng Replant Disease Working Group chaired by Dr. Sean Westerveld of the Ontario Ministry of Agriculture, Food and Rural Affairs.

Executive summary

Soil fumigants are pesticides used as soil treatments intended to control a wide range of soil-borne pests including insects, pathogenic fungi and bacteria, nematodes and weeds. Soil-borne pests are an important limiting factor for viable production of many annual and perennial crops, hence the use of soil fumigants has been viewed as essential to protect yields. Following the phase-out in Canada of two widely used broad-spectrum soil fumigants, methyl bromide (2005) and Telone (2011), a critical need for effective soil treatment alternatives was identified. Currently there are limited chemical fumigants available for soil-borne pest control, and growers are becoming increasingly concerned about the lack of adequate alternatives to replace the uses lost through product phase-outs.

Following a systematic assessment by Pesticide Risk Reduction, this issue was identified as a priority for development and implementation of a reduced-risk strategy to make available to growers effective alternative solutions which could be used as part of an integrated management system to manage soil pests.

Perennial crops in particular are seriously affected by the loss of these fumigants, mainly due to the fact that plantations remain in the same field for more than one year and the high prevalence of replant issues. For this reason PRR chose to focus its resources on ginseng replant disease.

Unlike other strategies which are led by PRR, in this case PRR joined as a member of the existing Ginseng Replant Disease Working Group which was established by stakeholders in 2013. The Program has contributed resources to address gaps identified through stakeholder consultations held in this forum.

A 3-year project (2014-2017) funded by PRR under this strategy generated new knowledge about several fungi associated with the replant disease complex and explored non-chemical management options for ginseng crops.

It is anticipated that adoption of new tools and practices resulting from this strategy will enable integrated management of replant disease and help growers transition towards a sustainable ginseng production.

Pest management and pesticide risk reduction issues

Telone (1,3-dichloropropene and chloropicrin) had been one of the main pre-plant soil fumigants used in Canada, particularly as an alternative following the phase-out of methyl bromide in 2005. Its label included over 110 uses to control mainly soil borne diseases caused by nematodes (approximately 40) and pathogenic fungi (approximately 70) in over 30 annual and perennial agricultural crops. Its removal from the market exposed a great need for replacement products, especially for use in soil preparation prior to perennial plantings including apple, raspberry, strawberry, high bush blueberry, grape and ginseng. Replant disease complex, occurring when susceptible perennials are planted into soil where the same or related plant species were previously grown, has been an area in critical need of alternative solutions.

Ginseng is a perennial herb grown primarily for its roots, which are a source of many health benefitting compounds. Globally, Ontario is the largest producer of North American ginseng, Panax quinquefolius, with approximately 99% of Canada’s total of 3,500 hectares of production, most of which takes place in Norfolk County. Ontario’s ginseng production represents a $240 million industry, with majority of roots exported to Asian markets.

Ideally, ginseng roots are harvested in the 3rd or 4th year, the last production year. The majority of fields are cropped only once to ginseng due to infestation with soil-borne pests which build up over the multi-year production cycle in gardens and which pose great risk to new ginseng plantings. With ginseng acreage increasing steadily over the last 25 years, growers are increasingly challenged to find new fields with suitable soil and conditions for viable ginseng production.

Several pest-related issues are known to limit commercial success of the ginseng industry. 1) While longer production periods increase yield and quality of ginseng roots, these can also lead to increased incidence and severity of soil-borne diseases in roots. Growers will harvest prematurely (approximately the 2nd year), not reaching full yield potential if diseases are expected to cause major damage in roots. 2) To establish new ginseng gardens, growers must go distances to find new fields which have not been infested by soil-borne ginseng pests as a result of previous ginseng crops, thus increasing production cost and affecting quality, when optimal soils are not found. 3) Given these impacts of soil-borne disease agents on ginseng production, the industry is highly reliant on soil fumigants. With the few options which remain available (chloropicrin, dazomet and metam-sodium) undergoing regulatory re-evaluation, the need for alternative solutions is critical.

In the fall of 2012, a ginseng industry meeting led by the board of the Ontario Ginseng Growers Association (OGGA) established replant disease and soil-borne pests in general as the top two priority issues in view of the loss of major soil fumigants. One of the action items coming out of this meeting was to set up an expert working group to tackle the replant disease issue. This presented an opportunity for involvement of PRR to assist the ginseng industry with solutions in the context of the PRR’s soil fumigant strategy.

Strategy

The section below describes only the activities supported through PRR in addressing the ginseng replant disease issue as part of the PRR’s soil fumigant strategy.

Working group consultations

The industry-led Ginseng Replant Disease Working Group (WG) established in 2013, continues work to meet the needs of the ginseng industry. The WG brings together pest management and crop production expertise to discuss potential solutions and coordinate resources towards the sustainable management of replant disease complex. Members include OGGA chair, board representatives and research managers, Ontario Ministry of Agriculture, Food and Rural Affairs specialists, AAFC scientists, University researchers, industry representatives and consultants. The group meets two to three times per year by teleconference and in person once per year.

Priority issues and gaps

Lack of knowledge on ginseng replant disease complex and the causal agent(s)

Replanting ginseng, even 20 or more years after the previous crop and with multiple cropping rotations to other plant species in between, has resulted in poor crop stands due to replant disease. A need to study the etiology of ginseng replant disease, investigations into the complex of pathogens responsible, and improved understanding of the disease was identified as a priority.

Lack of adequate control options in the tool-box

Restoring old gardens and rendering them fit for re-growing ginseng is a key to enable sustainable growth of the industry. Despite the chemical fumigants still available, the impact of replant disease remains a difficult issue to address. Effective, lower-risk treatment options and alternative approaches are needed to re-establish the soil health of old gardens and allow the safe and viable re-cropping of ginseng in these sites. A variety of control practices is needed to allow the adoption of integrated management approaches.

Methods to assess soil for the risk of replant disease and determine when soils are safe for ginseng re-cropping are also needed.

Strategy goals

Based on discussions and solutions proposed through working group consultations, PRR established the following goals and associated milestones for its part of the work to contribute towards solutions to the ginseng replant issue:

Goal #1: Generate knowledge on the etiology of replant disease

Milestone 1 - Elucidate the pathogen complex associated with replant disease in ginseng

Milestone 2 - Identify relationship between replant risk and number of years since most recent harvest

Goal #2: Develop lower risk alternatives to fumigation for reclaiming old ginseng gardens

Milestone 1 - Explore various non-chemical control options as part of an Integrated Pest Management (IPM) approach

Progress

A 3-year project titled PRR14-050 Development of management strategies for replant disease in ginseng production in Ontario was initiated by PRR in 2014 to address the above goals. This project has contributed by characterizing a number of fungi associated with replant disease complex in ginseng and the role of ginsenosides in this pathosystem. Also, management approaches such as biofumigants, biopesticides, biological and cultural practices and soil amendments were investigated within the project in an effort to improve ginseng re-cropping opportunities for old gardens. Work is underway to finalize the findings from this project.

In addition to supporting this work, AAFC is allocating resources through the Pest Management Centre’s Minor Use Pesticides to help growers gain access to chemical solutions to address the gap of lost soil fumigant uses. Numerous projects have been supported through this Program since 2003, with various chemicals and biocontrol agents being assessed to find, among others, effective and viable pre-plant soil treatment alternatives to old soil fumigants for ginseng, apples, carrots, and strawberries. The data generated is contributing to support the registration of several of these products, and the status of these efforts is available on AAFC’s website at: Minor Use Pesticides - Project Status by Crop.

This summary report will be updated as new information is made available.

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