Caltec Ag research confirms that high heat levels are more effective than fungicides to eliminate Powdery Mildew mycelium.
In a study just released by Caltec Ag of Modesto, CA. Agrothermal Systems® heat-treatments "...provided significantly better control/eradication of powdery mildew," than the standard grower solution of fruit wash and fungicides.
Few crop diseases are feared as much as Powdery Mildew which can devastate crops from wine grapes to leafy greens. Powdery Mildew is one of the primary reasons for the frequent use of fungicides as a prophylactic treatment to prevent spores from developing into mycelium. Once at the mycelium stage, chemical control is impossible with conventional fungicides, and can be difficult with the few materials available that can kill Powdery Mildew. Crops are frequently obliterated or harvests are limited and there are price reductions for wine grapes among other crops, that have visible levels of Powdery Mildew.
This study was done in combination with a two-year study aimed at reducing fungicide applications by alternating heat with fungicides. Tome Martin-Duvall MS, Senior Director of Research for Caltec Ag., took over the two-year project initiated by the late Dr. W. Douglas Gubler after his passing in July 2018. According to Martin-Duvall, "It was amazing to see how effective heat was at killing mycelium and there was no apparent harm or burning of leaves or fruit at these high heat levels averaging 500ºƒ. The heat is instantaneous, does not linger but lasts long enough to do the job. I could see where this could be done selectively at the first sign of an outbreak and stop further development of Powdery Mildew. Having worked to control powdery mildew all my career, this is a major breakthrough!"
Martin-Duvall also looked at the costs involved and made the following comments, "the propane used per acre to produce the heat was about 6 gallons per acre, or roughly $10. We did three passes at a total of $30 per acre. This compares with one fungicide application at $70." A second opportunity to test the use on mycelium was arranged at another location and it showed that only one pass of heat was effective. Martin-Duvall expects to do more work on this in 2019 on a vineyard near Fresno that always deals with PM outbreaks.
According to Marty Fischer, CEO of Agrothermal, "We have known for some time, that higher heat levels, higher than the normal range we use for Thermaculture, would be effective on mycelium, but finding the opportunity to actually test this in a replicated trial with a scientist to do the evaluation was pure chance. It resulted from a study we were doing where PM broke out in the control rows of Chardonnay. We were there to attack it with heat and provide outside scientific evaluations. Martin-Duvall’s work also showed that 3-4 applications of fungicide can be eliminated when a wine grower uses our basic protocol. lt has been determined that following the protocol will provide other valuable benefits such as insect control, assuring fruit set during cool wet bloom periods and improving fruit quality by increasing phenol and antioxidants through what we call instantaneous heat shock."
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