Resistance management of weeds with chemicals alone is no longer possible. Instead of new mechanisms of action, new mechanisms of resistance to herbicides are constantly being found. Palmer amaranth not only promotes mass in terms of seeds and growth, it also simply produces so many more receptors that the plants become highly resistant to glyphosate.

The only known strategy against the spread of this crop-damaging plant seems to be integrated resistance management using mechanical and physical weed control methods. Both scientists and crop.zone are working on this from different angles.

Lynn M. Sosnoskie of Cornell University, together with other scientists, has been studying the resistance of Palmer amaranth to pesticides in the US state of New York. (Link)

Glyphosate-resistant Palmer amaranth has been reported in more than 30 US states. It is one of the most important herbicide-resistant and crop-threatening weeds in the US and already has its own icon on the homepage of the world’s largest database of resistant weeds – where it is uprooted by hand (Link). However, the current work has revealed even more about the resistance mechanism.

While most resistance is based on mutation of a receptor for the herbicide, Palmer amaranth simply produces many more receptors. The herbicide cannot react with all the receptors. Using this relatively new mechanism, the plants became 42 to 67 times more resistant than control plants, continued to grow at a rate of 2.5 cm per day and produced millions of new seeds per female plant. It is feared that this resistance strategy could easily be transferred to other herbicides.

Further trials show that this process has already begun. Some other herbicides already work poorly. New herbicides are not on the horizon, and there is no guarantee that the mechanism will not work again. (Link)

Successful resistance management always involves a whole toolbox of measures from which the best ones must be selected. As the scientists working with Lynn M. Sosnoskie plan, an integrated weed management system needs to be developed that can (re)consider mechanical methods such as ploughing. However, tillage has significant side effects in terms of soil health, erosion and increased energy use. As there is no going back to the future, innovations such as electrophysical crop management should also be trialled and adapted to local needs. It remains to be seen whether large-scale application is a more effective solution than individual plant detection and treatment with electricity or lasers.

It is this integrated weed management that Cornell scientists are working on, as well as tools to help identify Palmer amaranth and strategies to reduce its spread by agricultural (Link). New strategies are therefore also challenging farmers, who have to deal even more intensively with individual weed species.

crop.zone makes its contribution by developing equipment that can be used over large areas for comprehensive electro-physical plant control without moving the soil.