I’ve been
following this idea of enhancing the activity of fungicides. Or it could be
described as enhancing the target pathogen’s sensitivity to fungicides. I have noticed that there is similar
research and information in both the agricultural arena as well as human
health. The results are the same. This is one of those true “synergy” or
“win-win” scenarios. When using a tool like chemosensitization – proper math
goes right out the window. One plus one no longer equals two – now we get more.
The basic
idea is to use lower risk materials with antifungal properties along with
conventional fungicides. What was
unexpected in the research was how well this approach worked. Each product on
its own has activity on the pathogen. When put together the pathogen control
was much higher than the control achieved with either product alone (and higher
than the separate applications added together). Control has been so good that
the researchers were able to use lower
rates of the fungicides and still achieve good control. With the cost of
today’s fungicides I think it would be easy to achieve a favorable ROI using
this chemosensitization approach.
I used the
words lower risk earlier and I want to elaborate on what I meant. The phrase
“lower risk” applies for multiple reasons. Safety – Lower risk refers to the
mode of action of the products. They are much safer for people and the
environment. Resistance danger - The materials being used to achieve
chemosensitization are essential oils, plant compounds, and microbial exudates.
Materials with these types of origins, having evolved as parts of plant and
microbial defense mechanisms, carry a lower risk of a pathogen developing
resistance. Especially when compared to resistance buildup to chemical
fungicides.
One compound
that consistently shows up in research is thymol
(2-isopropyl-5-methylphenol). I have run across thymol in both human health
research and plant pathology work. The names of some of the antifungal
medicines that thymol was able to make more effective in the human health realm
end in “…azole” just like many of our crop fungicides. The thymol-azole
combination completely stopped fungal growth at rates lower than when an azole
medicine is used by itself. The research even tested the combo against
organisms already resistant to the medicines. Thymol made the organism
susceptible to the fungicide again.
Thymol seems
to have most of its action on cell walls and cell membranes. The azole drugs and fungicides also have
activity on cell walls and membranes which may be why they work so good together.
Our bio-pesticide products from Huma Gro®
utilize thymol as a major component. For soil use there is ProMax™ which also gives
us a bio-fumigant action. For foliar use we have Proud3® with local systemic
activity and residual control that is rare for an organic product. Here is a
way to maximize your fungicide dollar, reduce application rates, and use an
inexpensive lower risk product that is geared toward supporting plant health as
well as harassing the pathogen and making it easier to control.
Research examples: Quadris®
(azoxystrobin) and thymol together had enhanced activity on Bipolaris sorokiniana, Phoma glomerata, Alternaria
sp., and Stagonospora nodorum.
Dividend® (difenoconazole) and thymol
showed enhanced activity on Bipolaris
sorokiniana, and Stagonospora
nodorum.
Folicur® (tebuconazole) and thymol showed
enhanced activity on Alternaria alternata.
