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"A gleaming, cold battle machine is on patrol, red glowing eyes ever searching for the enemy. The slightest movement focuses the attention of this guardian, enabling it to determine if the intruder is friend or foe. Suddenly, a stirring in the soil alerts those ever-watchful burning eyes. A tentacle is seen extending furtively towards an unprotected root, intent on infecting, dissolving, digesting and destroying it. Instantly, the T-22 springs into action, training weaponry on the invader and dooming it quickly to a vapory oblivion..." Science fiction? Not any more, because gardeners today can call on a real live T-22 that can help protect their valued plants. Read on. . .
..this bodyguard can have the spare room!
If any fungus could ever be said to be a multitasker, Trichoderma would be one of the leading candidates. Researchers have found various strains to be useful for production of enzymes, as biocontrol agents, in plant growth promotion, and as a source of transgenes. In this article, I'm going to focus on the biocontrol aspect of one particular strain, the T-22, or Trichoderma harzianum because what this fungus is best at is of great interest to us as gardeners.
Trichoderma is common in nearly all soils and their activity is favored by the presence of plant roots. Some strains are better at colonizing the root zone, or rhizosphere, than others. T-22, known as RootShield, is a hybrid strain developed to incorporate many qualities of the better strains into one fungus. This workhorse colonizes the rhizosphere readily, and even grows along as the host roots grow. The more abundant and healthy the plant roots are, the better the fungus proliferates. This relationship is mutually beneficial. The plant roots provide the rhizosphere as a hospitable spare room and board for the fungus while the fungus attacks any pathogenic fungi attempting to invade the root zone.
The thumbnail picture above, right, shows RootShield hyphae ( shown in green) associating with a plant root (shown in brown).
Trichoderma is neighborly and tolerant as well, getting along with mycorrhizal fungi and able to function well even in the presence of many chemical fungicides. In fact, some work I've done demonstrates that different biocontrol organisms are most effective when working together as a group rather than as "lone rangers" on solo patrol. A normal or healthy soil biota will have a quantity of different types and strains of fungi and bacteria, so using several biocontrol agents together is more like the state of normal soil than a single overpowering strain would be.
The ability to stay on duty when chemical fungicides are present is a boon because the biocontrol fungus cannot, by itself, help a plant that is already infected with a pathogenic fungus. First, the unwelcome invader must be evicted. Then Trichoderma can move in and provide preventive protection for the plant. So you see that the best time to utilize this biocontrol agent is before an infection strikes, not after.
The picture at left shows a RootShield hypha attacking and invading Rhizoctonia, a pathogenic fungus.
Best to keep this one on the payroll!
RootShield is most effective when multiple applications are used. You want the entire root system to be protected and a plant in vigorous growth can outstrip the ability of the fungus to keep up. This can leave some roots unprotected, so the solution is to make new applications as your plants grow. The commercially available formulation includes recommendations and instructions for the proper timing of these applications.
One need not worry where the payoff is for Trichoderma; natural root exudates from the host provide sustenance for the fungus as it grows. So in this manner, the plant being protected is taking care of the fungus payroll! The post assumed by Trichoderma confers upon it a sort of "squatter's rights", enabling it to fend off the pathogens more effectively. This is also the reason why applying this bicontrol after pathogen infection is not effective. In that case, the pathogen has already exercised the squatter's rights, feeding off the same root exudates but damaging the roots and excluding the beneficial fungus in the process. In the photo below, right, Rootshield hyphae can be seen coiling around plant roots, making themselves at home in preparation for their role as defenders against disease-causing fungi.
My plants say, "We want the right fungus among-us!"
Home gardeners and plant fanciers can now obtain their own Trichoderma harzianum T-22 in the formulation known as RootShield. Some sources are Gardener's Supply Company, Johnny's Selected Seeds, and Territorial Seed Company. Each of these sources offer the home and garden version of RootShield. Commercial agricultural and horticultural interests can obtain professional formulations from BioWorks, Inc.. Much more information about RootShield is available on the BioWorks website.
LariAnn has been gardening and working with plants since her teenage years growing up in Maryland. Her intense interest in plants led her to college at the University of Florida, where she obtained her Bachelor's degree in Botany and Master of Agriculture in Plant Physiology. In the late 1970s she began hybridizing Alocasias, and that work has expanded to Philodendrons, Anthuriums, and Caladiums as well. She lives in south Florida with her partner and son and is research director at Aroidia Research, her privately funded organization devoted to the study and breeding of new, hardier, and more interesting aroid plants.
Posted by Indy (from Alexandria, IN) on February 27, 2008 at 9:23 PM:
I have used Root Shield 3 seasons.......mixed into the seed starting mix for melons and tomatoes. The reason I use it is that I have raised melons for many years and it is hard to keep fusarium wilt down to decent levels in some years....without aids like T-22. I have used the left over supply as a booster drench later....need to learn better when to do this as melon roots really grow.
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Posted by LariAnn (from Miami, FL) on February 27, 2008 at 9:43 PM:
I've used T-22 on difficult Alocasia plants like A. nebula 'Imperialis' and others. I find that applying every one to two weeks works for these plants. I haven't grown melons, though, but if the roots grow fast, I would guess you need to apply the T-22 more often.
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Posted by Fitsy (from Hayesville, NC) on March 8, 2008 at 5:17 PM:
Thanks very much for this information. So much about
nature and gardening is mysterious, and enlightenment
is wonderful!
Fitsy
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Subject: More research with T22
Posted by starlight1153 (from Seale, AL) on February 27, 2008 at 8:21 AM:
Was a very interesting read LariAnn. Have you been doing any research with T22 yourself? I have a research project that I am working on titled Biological Control Using Trichoderma harzianum as a Liquid Drench on Broccoli and Melon Seeds. (sorry don't know how to italize on here yet).
I am investigating the capabilities of Trichoderma harzianum Rifai 1295-22 (T-22) s a souble pre-seed drench on broccoli and melon seeds on field soil and greenhouse potting mix.
If you have an experimentation going on, I would be interested to learn some of your finds. I hope to have my paper finished in a few weeks. it has been an interesting experiment and am getting ready to start pulling plants and observing and photographing the roots soon.
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Posted by LariAnn (from Miami, FL) on February 27, 2008 at 9:53 PM:
I did do a research study last year using ten different Alocasia species, two replications and nine different treatments, plus a control. The work was done in conjunction with the University of Florida Tropical Research and Education Center, Homestead, Florida. This extensive study ran for four months but I had to terminate it due to adverse weather events. The results were not conclusive enough for a paper, but I did learn quite a bit from the data acquired from it.
My most important finding was that several biocontrol products used together were, statistically, more effective than products used individually. One of the best performing products used individually was the T-22 (RootShield).
Posted by doccat5 (from Fredericksburg, VA) on February 27, 2008 at 7:58 AM:
Lari, thanks for sharing this. I regularly use BT for caterpiller control, but didn't realize there was something for fungi. Really appreciate the information. Thanks for sharing.
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Posted by Dutchlady1 (from Naples, FL) on February 27, 2008 at 11:57 AM:
So interesting.
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Posted by pajaritomt (from Los Alamos, NM) on February 27, 2008 at 8:04 PM:
I learned to pick safe mushrooms for eating a few years ago from a mycologist and learned how important fungi were to plants and to us all. I am so interested to see how we can increase the activity of these fungi in our soil. Nothing like more ways of making our plants healthy! Please share any other information along these lines that you come up with.
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Subject: I always enjoy your articles
Posted by Illoquin (from Indianapolis, IN) on February 27, 2008 at 5:52 AM:
Dear LariAnn,
I always enjoy your articles - you have a unique way of making even the dullest topics very interesting.
Suzy
P.S. That last B&W image should be an ad for an upscale dancing school.
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Posted by LariAnn (from Miami, FL) on February 27, 2008 at 6:51 PM:
Suzy,
Thanks so much for the compliment and encouragement! I like to share the wonder I experience when I learn new and (to me) exciting things about my plants.
