Chemosensitization

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.