By Barbara Kessler
Green Right Now
Discerning diners would probably not find this much of a topic for dinner discussion, but back in the fields where their broccoli is grown, fungus can stop a good crop cold. Most farmers apply fungicides to deal with the problem, but fungicides, a subset of pesticides, can kill beneficial organisms and cause environmental damage in the course of attacking the problem invader.
Fungicides, like other pesticides, also can wind up growing better fungus as the disease adapts to fend off the poison. The fungus becomes resistant to the pesticide, and creeps back ever-more resilient. Which requires more chemical treatments; which can increase resistance; requiring more treatments…
To try to break this cycle, researchers in Canada have been developing new “green” fungicides that are less environmentally damaging because they go in for a targeted kill. This surgical approach plays off the plant’s own defense strategy by attacking the fungal infection as it ramps up to break through the plants defenses. Effectively, the new eco-fungicides, called “paldoxins,” disrupt the fungus’ response to the plant.
It works like this: The plant reacts to the encroachment of the fungus, and puts up a barrier of defenses; the fungus reacts by hitting those defenses with its own chemical reaction.
The paldoxins or anti-fungal agents intervene, rendering the fungus unable to hit back at the plant. Instead of dropping a bomb – the old way — which can damage the plant and the beneficial organisms that assist its growth, they go in for a guerilla attack, selectively disrupting the fungus’ ability to fight through a plant’s defense mechanisms. The researchers refer to these agents of targeted destruction as “inhibitors of fungal enzymes” (a term that we non-chemists will thankfully not be tested on).
The benefit is clear — the surrounding landscape is not harmed by paldoxins. Also, in theory, the fungus has been outwitted and should not develop defenses to thwart this type of intervention.
These developments could help save row crops, in addition to produce, according to a press announcement about the findings, released at the 237th meeting of the American Chemical Society over the weekend.
“Conventional fungicides kill constantly,” said study leader Soledade Pedras, a chemistry professor at the University of Saskatchewan. “Our products only attack the fungus when it’s misbehaving or attacking the plant. And for that reason, they’re much safer.”
Not everyone will be convinced. We’ve been down a similar path with other types of pesticides, specifically those that tunnel into a plant’s biology, working from the inside out to thwart pests. But those types of pesticide/plant interventions are different in a key way — they aim to alter the crop plant itself through genetic modifications.
This approach confuses the invading pest, without interfering with the biology of the crop plant, which appears to be a truly safer; plant-preserving, instead of plant-altering approach.
Pedras’ group has developed six synthetic versions of the paldoxins and successfully tested them in the lab on crucifer plants, including rapeseed plants and mustard greens. They plan field tests on other crops, including grasses such as wheat, rye, and oat which are more difficult to protect with fungicides.
The study was funded by the Natural Sciences and Engineering Research Council of Canada and the University of Saskatchewan.
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