Allium white rot biostimulation project-Part 2
2015 marks the culmination of a four year study (FNE11-721 and FNE13-782) of biostimulation techniques as a potential management tool of the garlic (allium) disease Allium White Rot (AWR). AWR is a persistent fungus, affecting all allium crops, that produces resting bodies called sclerotia, rather than spores, and these resting bodies can survive in garden/farm soil for up to 25 years. We aquired AWR in 2004 as the result of purchasing seed garlic from out of state – and we unwittingly introduced AWR into our gardens. After identifying the disease and experienceing significant crop losses in 2007 and 2010 we embarked on this study.
Biostimulation is a technique that introduces allium juices and/or ground up plant materials, that contain the active plant chemical substance allicin, into the soil thus stimulating the resting sclerotia to germinate. But without actual plants available to complete the life cycle, the germinated sclerotia die, thus gradually reducing the amount of infection.
We designed a study to test these two biostimulation applications, as well as control beds without treatment, and with guidance from our main mentor Dr. Fred Crowe, and continuing encouragement from Eric Sideman (MOFGA) and Dave Fuller (UMaine Extension) we’ve completed the study. We applied garlic juice and ground green plant material (from each previous years harvest), or no treatment in the control beds, to bed sections in 2011 through 2014, annually, each spring. The beds were then planted to crops other than alliums and maintained and harvested each fall. With help from the laboratory Nematodes, Inc., in California, we’ve been able to track the numbers of viable sclerotia in soil samples from each bed, taken each spring, and chart the decrease in numbers.
Our goal in 2015 was to make test plantings in all the beds in our study. In late May and mid-June we planted the test beds to three crops: two were plug-planted; pearl onions, designed to be a very early crop; and storage onions, designed to be harvested much later. In mid-June we planted our third crop, direct seeded scallions. The plantings were entirely random, spread over all 18 bed sections At the appropriate times – mid-July for the pearl onions, September for the storage onions, and October for the scallions, we harvested and subsequently delivered crop samples to the University of Maine Insect and Plant Disease Diagnostic Lab. The results of these analyses are incredibly encouraging!
The photos we’ve uploaded are of the bed sections showing the plug planted onions, the just planted scallions, and the scallions just after germinating.
The results of the lab tests at the University of Maine Insect and Plant Disease Diagnostic Lab are very gratifying. The pearl onion harvest showed only two samples (out of 36) with any AWR infection, and the results were the same for the storage onion harvest. And as I had hoped, the scallion harvest showed NO infection!
The growing season this year was very beneficial to allium crops as there was plenty of rain in June. All of our allium crops benefitted from the weather. As a result I feel this was a prime year to make the test plantings.
The next step is to compile and assess all the lab and planting results and create a statistical report. I will have help from Tom Molloy at the University of Maine Extension to do this part of the project.
- Harvesting Pearl Onions
- Pearl onion lab report
- Copra Onion lab report
- Scallions CLEAN lab report!
- Harvesting Copra onions
- Scallions ready to harvest
Impacts and Contributions/Outcomes
Over the last four years I have taken EVERY opportunity to educate folks on the importance of understanding garlic and allium diseases, especially the diseases that are new to New England, including AWR. Most recently I spoke at the New England Vegetable and Fruit Conference (December 15, 16, and 17, 2015) in Manchester, New Hampshire. I was asked to participate in a session that centered on creating on-farm research projects, and specifically SARE grants. I was asked to outline our study in detail, our progress so far, and what I felt would be the impact of our study. I was able to describe in detail the design of our project, the challenges we found/tripped over, and report on the raw results of our test plantings. The talk was very well received.
I am scheduled to speak at the NOFA Mass Winter Conference, January 16, 2016, on the subject of Growing Great Garlic. Along with cultural and culinary information, I will present a detailed program on disease id and management, including preliminary results from our statistical analysis.
I plan to attend the 2017 IFOAM World Congress (as I have every three years since 2002) and will propose a poster or presentation for the Congress in Delhi.
UMaine Cooperative Extension
138 Pleasant Street
Farmington, ME 04938-5828
Office Phone: 2077784650