At the 2015 ITC in Orlando Florida the last talk of the conference was by Dr. Glen Percival on Systemically Induced Resistance (SIR). He reported on his research using the fungus Trichoderma to successfully treat Apple Scab and Armillaria spp. in Great Britain.
At the 2016 ITC in Washington D.C., two studies done in Italy were presented using Trichoderma to treat diseases. One treated tree was an historic veteran. They grew the disease organism found in the veteran tree, tested some 60 different strains of Trichoderma in vetro and picked the best performers to apply to the tree. In both of the studies, Trichoderma suppressed the disease issues.
At the 2017 ITC in Columbus OH, Dr. Glen Percival presented another study in which Trichoderma suppressed Armillaria. His talk was on the Use of Biologicals and Their Potential for Soil Borne Disease Management.
At the Oak Wilt Qualification course in Fredericksburg TX September 2017, Gene Gehring stated that he often only needs to do a single application of propiconizol and is able to follow up in two years with fertilization to help with the recovery process. He does a second application of propiconizol only when he has recurring symptoms, which is not often.
In June of 2014, we had treated 5 Oak Wilt symptomatic Live Oaks in San Antonio with Alamo (a propiconizol product) applied at 20 ml/dbh, injected into roots and root collar. One of the Live Oaks was about 50-60% defoliated (we recommended not treating), three had abundant symptomatic leaves (veinal necrosis) with good canopies and the fifth did not have symptoms but was within 50 feet of the symptomatic trees. All trees responded well to the injections and stabilized.
The next year (2015) a June inspection discovered all five trees with symptomatic leaves and we recommended re-treatment. The client declined. I was aware that the organic folks used Trichoderma from whole ground cornmeal to suppress fungal diseases in tomatoes and asked the client if they would let me try cornmeal water and cornmeal broadcast to see if we could get a SIR reaction for Oak Wilt. Since it was free, they agreed.
For the cornmeal water or tea, we used one cup whole ground cornmeal per gallon of water. We let the cornmeal soak in the water for about 6 hours and then dumped the cornmeal water in the shallow trench around the base of each tree, the well we created with the air spade to expose flare and roots.
We used two buckets or 10 gallons per tree. On the fifth tree, we also did a broadcast under the entire branch spread of the tree using 20#/1000 square feet.
I returned in two months to inspect the treated trees and there were no symptomatic leaves on any of the five Live Oaks, in the tree or on the ground.
In 2016, we again treated all five Live Oaks with a cornmeal drench, but I charged for the treatment, $125 plus tax for 5 trees. By then we no longer used the broadcast method because of issues with squirrels, deer, and fire ants. We had another year with no symptoms. All trees were stable but all look like they have battled Oak Wilt.
In 2017, the client decided to do the treatment themselves and save the $125. The trees were stable in 2017 and 2018. (Keep in mind Gene’s experience about a single treatment being effective and all that is needed).
Since 2015, we have used a cornmeal drench with every injection that we do. We have the client do follow up annual drenches. So far, we have not had to do a second injection on any Live Oaks that have been treated this way. A note: we do very few injections for Oak Wilt, so this is not much of a survey.
When a client declines injection, we have tried just using cornmeal water alone and the results have been mixed. In my opinion, just using the Trichoderma is not reliable. Just the SIR reaction does not appear to be enough to reliably suppress Oak Wilt. Our success has been drenching in conjunction with Alamo injection.
Another note of caution, this is not science and in no way even approaches a controlled study. It is purely anecdotal. The nice thing is that it costs almost nothing. We can buy 50# of whole ground cornmeal for $10. If you buy from a good nursery it will cost $20. Put some bay leaves in the bag to keep out the flower beetles and you can treat a lot of trees with $10 of product. You can mix the buckets while you wait for the trees to take up the propiconizol injection, and dump the water after you remove the tubing. The cornmeal only needs to soak for 1-2 hours to get the Trichoderma into the water.
We have also started using the cornmeal water for other fungal diseases including Hypoxylon Canker, both Ganoderma, and Kretzschmaria (charcoal rot or burnt crust rot). Dr. Percival mentioned in his 2017 talk that Trichoderma was also producing an antibiotic, so we have applied the drench to trees with Crown Gall. So far, we have been pleased with the results and clients call asking for an annual re-treatment or ask for direction so they can mix their own. I had a medical doctor laugh at us when we applied Trichoderma to two mature Sycamore on his ranch. He called 6 weeks later to ask for mixing directions. I plan to try some this summer on Cedar Elms at the Head Waters Reserve to see what it will do with BLS.
I understand this is not the kind of science we need. Who is going to sponsor a study for something this simple that has no chance of being profitable on a large scale. I write this not to say we have a cure for any disease. SIR is real and it is working. As pesticides become less effective, as they become banned for use, as they kill beneficial organisms and pollinators, we need alternatives. That is why the research that is done is coming out of Europe and Great Britain where agrochemical use is so restricted. They are also working with Salicylic Acid (active ingredient in aspirin) for SIR effects and several other products and organisms.
If you get a chance, play with Trichoderma and see what it will do for your disease control. As Dr. John Ball teaches, all trees in an urban environment are stressed. Trees have developed marvelous systems for combating disease. We need to use or enhance these natural systems whenever we can. Give Trichoderma and SIR a try and let us know failures and successes.