Management of Allium White Rot

Final Report for FNE11-721

Project Type: Farmer
Funds awarded in 2011: $8,301.00
Projected End Date: 12/31/2012
Region: Northeast
State: Maine
Project Leader:
Amy LeBlanc
Whitehill Farm
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Project Information


The intention of our 2011 SARE grant was to test a biostimulation program, for at least two years, with the goal of gaining management/control of Allium White Rot (AWR). As AWR is the most devastating allium fungal disease, lasting as dormant sclerotia for up to 25 years in soil, we felt we needed to test biostimulation here in Maine.

We have made tremendous progress over the course of the last two years.  To be complete, the study should take place over the course of four years, using a crop rotation (excluding alliums in the beds used for the study) that is typical on organic farms.  We have since earned a second grant to complete the study for the full four years.

Initially we chose 6 raised beds, in different areas of our gardens, each with known AWR presence (garlic crops had failed spectacularly in all 6 beds, please see photo).  We divided each bed into three sections with solid wood dividers.  

The study was designed to test two biostimulants – garlic juice diluted in water, and ground garlic green plant material, and a control section with no treatment.  We designed the sections and treatments so there would be complete replication.

Three lab tests were performed – assays of the number of dormant AWR sclerotia in each sample and the number of sclerotia that actually germinated. The initial assay, in the spring of 2011, served as a baseline assessment of the presence of AWR in all six beds and 18 sections.  Then two more assays were performed, in the spring of 2012 and 2013, by Nematodes Inc., to assess the amount of AWR pathogen – sclerotia – in the soil AFTER the first two treatments.

The tests show a significant drop, of 91%, in the amount of pathogen found. In fact the drop in numbers, both of sclerotia and the number that germinated, is dramatic. There are many variables involved – depth of sampling, pattern of sampling across each bed as examples – and I feel that further testing is necessary.  We will continue the study for two more years, taking the variables into consideration.


Whitehill Farm is a small diversified and Certified Organic operation.  We primarily produce vegetable seedlings for local home and market gardeners.

The gardens are ~75 4’X10’ wooden sided raised beds in several locations on our hillside.  We also have a 26’X48’ hoophouse and several smaller greenhouse structures, all heated seasonally, for our seedling business.  All of these spaces are planted to crops during the summer and fall, and the large hoophouse is used for a brief time in the fall/winter for Asian greens production.

Our garden crops include trial varieties for the seedling business, herbs and garlic for our value-added products, and our own family garden. Altogether the area actually farmed in the summer months is less than a quarter acre. 

Because poultry specialize in scratching in gardens, and probably contributed to spreading AWR, our hens are now fenced in and we do rotational “grazing”.

Until AWR became a serious issue in 2010, garlic was a major cash crop for us. We planted between 2,000 and 2,500 garlics every year to be harvested and sold as planting stock and to be used in our products.

The presence of AWR put that production into a tailspin, including a significant financial hit, and we knew we could not sell seed garlic unless we were able to ensure it to be disease free.  In order to continue growing garlic we have constructed 5-6 new beds every year, in an area completely removed from the AWR contaminated beds.

We initially got Allium White Rot on seed that we bought from out-of-state. Once on the property it is very easy to move. People (think hands and boots), tools, a steep slope, rain, chickens, compost, and all kinds of equipment can move the pathogen very effectively.  Parallel to the biostimulation study we designed a sanitation protocol to limit the spread of the disease.

The advisors for the project were involved primarily with designing the biostimulation plan. I continue to be in contact with all of them reporting progress and tossing around new ideas.

Dr. Fred Crowe, Emeritus, Oregon State University, has done extensive work with biostimulation with farmers in both Oregon and Canada.  He provided inspiration and the nuts-and-bolts assistance with planning the biostimulants and methods of application.

Dr. Steven Johnson, Crops Specialist, University of Maine Cooperative Extension, and David Fuller, University of Maine Agriculture and Non-Timber Forest Products Extension Professional, are currently working on a SARE project to produce certified disease free seed garlic. They were both involved in helping design my project and have been monitoring it along the way.

In addition Dr. Eric Sideman, Organic Crop Specialist at MOFGA, has been a trouble-shooter and sounding board.



Project Objectives:

Our goal, over the course of this grant, was to determine if a concentrated program of biostimulation, using materials produced on farm, could be an effective management tool for AWR.  We framed this as a program that would fit into the normal 4 year crop rotation pattern of a small Organic operation.

The results thus far, showing a full 91% drop in the amount of assayed AWR pathogen, are very encouraging.  In the second phase of our study (FNE13-782) there will be two more lab tests, two more applications of biostimulants, and a final planting of allium crops in all 18 sections.

A big part of our efforts have been to contain and prevent any spread of the AWR pathogen on our property.  To date all allium crops - planted in beds not known to be infected - have matured successfully with no sign of AWR.  This reinforces the importance of a strong sanitation program that is followed carefully, side-by-side with the biostimulation program.


Click linked name(s) to expand/collapse or show everyone's info
  • Dr. Fred Crowe
  • David Fuller
  • Dr. Steven Johnson
  • Dr. Eric Sideman


Materials and methods:

[Before applying for our first grant I began researching biostimulation and it became obvious that I’d need to prepare for any applications. So in July of 2010, when we harvested the healthy portion of our garlic crop, we ground up the healthy green plant material with water and froze it to use the following spring.  Please see photos 1, 2, 11, and 9.]

[Tests for the presence and subsequent germination of AWR sclerotia can only be done in the spring. As the life cycle of Sclerotium cepivorum requires a period of dormancy, the assay and subsequent germination in the lab need to be after this dormancy, and after the dormancy breaks with warm weather/soil.  The rhythm of the seasons here in Maine includes a full winter for dormancy of the fungal sclerotia. After the soil warms and can be worked the samples can be taken and the biostimulation applications applied.  After the growing season, when beds are planted to non-allium crops and harvested, the cycle begins again.

Biostimulation is a process where a biological product - in our case garlic juice or green garlic material - is used to trick an organism into germinating.  In the absence of a host plant the organism dies.  The garlic juice or green plant material is incorporated into the soil and the normal chemical exudates of the juice/green material stimulate the AWR fungal sclerotia and cause them to germinate.  However, since there is no actual plant for the sclerotia to live on they die.  The result is a reduction of pathogen in the soil.]

Spring of 2011

Early May – We constructed the dividers in all the beds to be tested. The sections are numbered (the Bed numbers and section numbers correspond to the numbers on the lab test sheets) and there is a randomized assignment of biostimulants and controls.  Please see photos 8, 12, and 13.

Very early June - First soil samples taken for baseline AWR assessment, when the soil had warmed.  We dug into each section, in at least 6 different places, taking soil at all depths up to 10”. We thoroughly mixed those samples from each section, and then packaged a half gallon sample from each section to send to the lab.  All 18 samples went to be tested at Nematodes, Inc., in Selma, CA, a lab that specializes in testing for Allium White Rot.  

We then prepared and applied the first treatments.  We made fresh garlic juice (using a juicer) from purchased garlic and applied the juice diluted in water – per Dr. Crowe’s suggestion, “with a strong garlic odor”, a half cup per 4-gallon sprayer load. We sprayed the water/garlic mix and simultaneously cultivated until the soil was evenly wet at least 6-8” deep. Incorporating the garlic juice and water quickly is important as the garlic is very volatile.  Please see photos 14, 15, and 16.

We also dug in thawed green garlic plant material (prepped in July of 2010), mixing it thoroughly into the soil to a depth of about 6-8”.  Please see photos 17 and 18.

In our initial proposal we planned to apply a second round of garlic juice and green material later in the season.  This has not happened as it is not practical - nearly impossible - to try cultivating 6-8" deep while other crops are maturing in the beds.

Since we are using hand tools we had to develop a method to do the applicatons that was fast and effective.  We have found that loosening the soil first, with a pitchfork, and then cultivating with a claw while the juice is being sprayed works very well.  Similarly, we loosened the soil and then thoroughly dug in the ground up green material, incorporating it to 6-8”.  We then planted the beds to non-allium crops, following our rotation plans for the year.  Please see photos 19 and 10.

Springs of 2012 and 2013
We repeated the entire process of taking samples for testing, doing the biostimulant applications, and planting normal non-allium crops

The resulting assays of AWR show significant improvement in the amount of pathogen.  Please see images 3, 4, and 5

During this entire time we have been following and streamlining our sanitation protocol.  No garden activity takes place without cleaning materials – we carry a bucket set up with soapy water and a brush to every task.  We clean tools, hands, wheelbarrows, boots - everything that touches soil - before moving on to any next task.  Although this sounds tedious, we’ve gotten to the point where it is “just the thing we do”. We have a discreet set of tools for our new garlic area (see below), which simplifies the cleaning needs. At the end of the day, or when the cleaning bucket needs it, we dump the soiled water into a 4’ deep sinkhole that we have dug for this purpose.  Then any further rinsing of tools, equipment, or buckets is done right into the hole.  Please see photos 6 and 7.

In order to have a garlic crop for our value-added farm products we’ve been building new beds every year.  By adding 5-6 beds every year we’ve been able to keep pace with our rotation and begin building up our seed crop again.  The new beds are up hill from the contaminated gardens, are filled with Certified Organic raised bed mix (a mix of loam and composted cow manure) that we are bringing in, and as part of the sanitation protocol have their own discreet set of tools.


Research results and discussion:

The outcome so far is very encouraging.  We have effected - with two biostimulant applications - a 91% decrease in the amount of AWR pathogen.   The three assays show a marked decrease in both number of sclerotia per sample and the number that actually germinated in the lab. Please see Image 6 - Table A - where I've listed the actual number of sclerotia found, for each bed, listed over the three tests.  The total found in the baseline test (47), compared with the total lost over the subsequent two years (43), shows the 91% decrease.  Of interest however, is the increase found in two beds, over the same time.  This indicates that there are variables that we hope to deal with over the next two years.  Please see Image 7 - Table B - where the number of sclerotia that germinated in the lab are tracked for each bed, over the two year time period.

Apart from the initial labor to set up the beds, the process of taking samples and applying the biostimulants has gotten easier with each year. In the spring of 2013 we reinforced the sides of several of the beds by bracing them with rebar stakes. We will probably do another round of bracing in 2014 as in the nature of things the wooden sides and corner joints deteriorate.

The most important consideration continues to be sanitation. We began with a protocol – suggested by Dr. Crowe and refined with advice from Dr. Johnson – that meant we would prevent the movement of all soil (and pathogen) during planting, cultivation, weeding, etc.  Every tool, all equipment, hands, and boots are washed between bed sections when working with the SARE beds.  Please see Images 1, 2, 3, and 8.

We did have one unanticipated expense.  During the growing season of 2011 we realized that our own compost bins were potentially contaminated, so we had a local contractor come in - in January of 2012 when the ground was frozen with very little snow cover - to remove everything. The load of compost, construction materials, and soil from under and around the beds, is now part of the fill under a new office building. We’ve started over with new compost bins in a different location.  Part of the sanitation protocol now involves separating potential compost ingredients: nothing from the SARE beds goes into the compost.  Please see Images 4 and 5.

The addition of new beds in new areas means that we will be able to increase our garlic crop every year.  This will eventually restore our income from garlic.

Our project will be continuing as we were awarded a second grant to take the project across 4 years.  So at this time all our results should be considered to be preliminary.

Research conclusions:

With the completion of this grant we have shown progress in developing a management program to combat AWR.  The positive results we have are the result of a program of biostimulation that is accessible for gardeners and small farmers.  It is that accessabily that will make it easy for gardeners to use this practice if they have the need.

We will continue to use this opportunity to educate other farmers and gardeners about allium diseases.  We have been very open about how we got AWR in the first place, the severity of the problem, and how it can be spread.  We have not spread the disease beyond our gardens, and we’ve used our situation as a springboard for educating as many gardeners as possible. 

Having a very positive result so far is gratifying, and all the gardeners we’ve talked with are very appreciative that we are doing this research.  The concept of biostimulation is simple, has been tested in other countries (primarily the UK), and appears to be a viable option should one have or acquire AWR.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:

We have been using our problems with AWR and our SARE Grant as a continuing opportunity to educate gardeners and farmers about the allium, particularly garlic, diseases that are becoming problems in Maine.  Our spring seedling customers frequently purchase seed garlic in the fall.  Every seed garlic sale is accompanied by an informative handout about planting, growing garlic well, and understanding disease and insect pests.  Please see Document 1, Garlic Handout

During the 2014 and 2015 growing seasons we will be presenting the results of our study in addition to the general information previously on our handouts.  Biostimulation, combined with a good crop rotation plan, is a viable way to manage allium disease.

In July of 2011 the Lewiston Sun Journal ran a very good article about garlic diseases.  Dr. Steve Johnson and Dave Fuller contibuted the bulk of the content, but there was also a good review of our SARE Grant plans as well.  The article appeared the Thursday before Open Farm Day - the 24th - and prompted a lot of folks to visit and learn more.  Please see Image 5, Lewiston Sun Journal article.

We open our farm to the public for Open Farm Day, held in July every year, and this gives us another opportunity to talk with folks about protecting their gardens and crops from allium diseases.  Please see Documents 2 and 3, Open Farm Day handouts from 2012 and 2013.

I attend the annual Agricultural Trade Show, held in January every year.  In 2012 I shared in a presentation led by Dr. Steve Johnson. This was an opportunity to speak to a large number of MOFGA farmers and gardeners about our AWR problem and progress with biostimulation.  Please see the Image 4, Ag Show 2012 program.

At MOFGA’s 2013 Spring Growth Conference, I participated in the day-long program, "Garlic in Depth". Three farmers shared a session and I was able to present a bit about how we grow garlic in raised beds and how we are working on the biostimulation project.  Please see the Image 6, Spring Growth Poster and Document 7, MOFGA article "Garlic in Depth"

The NOFA Summer Conference and local Adult Ed classes have also provided opportunities to share what we are learning. I present an Organic Gardening class every spring and a garlic how-to class every fall for our local Adult Ed program.  Besides the usual how-to and recipes, I’ve taken these opportunities to have a short but detailed discussion of the garlic diseases that gardeners and growers need to know about.  Please see Image 8,  Adult Ed brochure cover and Image 9, Adult Ed class descriptons.

I plan to publish our preliminary results in MOFGA and Extension newsletters.  We will then present final results – in 2015 – at the conclusion of the second grant.

Project Outcomes

Assessment of Project Approach and Areas of Further Study:

Potential Contributions

At this time making farmers and gardeners aware of AWR and how to prevent getting it in the first place is of primary importance. The results of our study show that it is possible to make signicant inroads to reduce the presence of AWR if it becomes a problem.  

Since we are experiencing positive results with our project I have begun to talk with farmers who farm on a much larger scale. After several conversations with farmers who plow and till with tractors, they have convinced me that the garlic juice biostimulation application could be done with existing equipment and could be very effective.  Thankfully none of the farmers I talked with are experiencing AWR, but after a detailed conversation they each agreed that the equipment they already own and use could be used for biostimulation.  As we are a very small-scale operation and can’t test this ourselves, this is a project for another SARE Grant!


Future Recommendations

Our study has definitely answered some key questions.  Yes, biostimulation can be done easily in a small organic system, with materials prepared on-farm.  And yes, biostimulation shows promise as a management tool for AWR.

I feel the next best step in this research will be to test the biostmulation program on a much larger scale.

Our study is still in process, and so ultimate answers are yet to come. The preliminary results are very encouraging and we will continue the study as planned while continuing to streamline some aspects.  We will take more care to address the variables in taking samples, including sampling from all the edges of the beds as well as the actual practical planting areas.  In addition we will continue to work on our sanitation protocol, making it an integral routine for everyone who works with us.

I am anticipating and planning to continue promoting our interim and final results to a varied audience.  I actively participate in MOFGA events – the Common Ground Country Fair, the Farmer-to-Farmer Conference, Spring Growth, and the Farm and Homestead Day.  These are events where I will be comfortable making a presentation about our research. It will also be well within my purview to write an article for the MOF&G, MOFGA’s quarterly magazine.

I am a regular contributor/presenter at the NOFA Summer Conference and at various state NOFA Winter Conferences.  In light of being awarded the second grant, I will wait until we have final results to take our findings to that audience.  The New England Vegetable and Fruit Conference is held every two years, and the next one will be in 2015.  Although it is held in December, I may be able to make a presentation there. If not 2015, then perhaps in 2017.

I have been attending the IFOAM World Congresses (2002 to the present), held every three years, and I will propose a poster presentation outlining our research for the 2017 Congress.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.