Last week I attended the Ontario Certified Crop Advisor Annual Meeting and Conference. It's always an interesting few days as the sessions can be very scientific or political and it's only open to CCAs.
One of the most interesting sessions at the conference last week was presented by Doctor Clarence Swanton who is a professor at the University of Guelph.
A few years ago, Dr Swanton first introduced us to the idea that a corn plant can "sense" weed comeption and alter it's growth. These findings led to the establishment of the critical weed free time for corn seedlings.
Now, he has expanded his research to determine what exactly makes the corn seedling change and how we can prevent it from happening.
-a corn plant seedling can sense competition by the far red light that is reflected off of anything green growing close to it (around 8cm). This includes other corn seedlings. Stubble and trash do not reflect the far red light.
-Even when underground the roots and shoots can sense the far red light up to 2cm deep depending on soil conditions and subsequently alter their growth before they are even out of the ground.
-The reaction to the far red is a release of free radicals (basically an atom or molecule the is very ready for a chemical reaction). Hydrogen Peroxide (H2O2) is one such free radical that is released and then is oxidized in the plant tissue. This can cause alteration of DNA, oxidation of proteins and lipids and alteration of plant metabolism. The amount of H2O2 in the leaves and roots can be measured as an index of the plants reaction to the far red light.
Now here is where it gets really interesting. Dr Swanton has found that treating the corn seed with Thiamethoxam (Cruiser, Syngenta) reduced the amount of H2O2 in the seedling, and resulted in no altered seedling growth when exposed to the far red light from weed competition.
So the main take away here is not that if you have Cruiser treated seed you can let your field get weedy and spray at 8 leaf corn. Rather, that some seed treatments do more than just protect the seedling from disease and insects and are a valuable part of integrated weed management.
Other thoughts
This is phenomenal research and we are very lucky to have Dr Swanton working on this for Ontario Agriculture!
