Although this spring, in many ways, did not go as planned, it provided an important reminder as to what can happen when mother nature steps in and decides she’s going to throw a curve ball. For many, the crop went in wet and stayed wet. Conditions staying wet was a benefit in many regards, no crusting on the heavier ground and no further crop stress due to droughty conditions on the sandier soils, but it also meant many couldn’t get back into the field to apply their “pre” or early “post” herbicide programs on time.
In most cases we were able to adapt, changing to products with a longer post window, but for some a residual chemistry never got applied and we played catch up the rest of the year.
It’s important to respect that even when you have practiced proper weed control methods such as rotating chemical families, tillage where needed and cover crops, the weed seed bank takes years to deplete. Canada fleabane can live in the soil for two - three years, common ragweed five years, nightshade eight - ten years and velvet leaf an impressive (or terrifying) 15-20 years, but some populations have survived as long as 40 years. The point here is that when we fail to stay on top of the weed pressure, it will show itself.
Fleabane pressure in Xtend soybeans
Sometimes we are “euchred” by environmental conditions and there isn’t much we can do. For example, this Xtend soybean field received plenty of rain following planting the beans quickly took off (1). We were dealing with more green material, less soil to target and more sensitive crops emerging in neighbouring fields every day until it was too late to apply dicamba.
The custom operator, understandably, did not want to risk any off-target movement so a decision was made to switch the chemical program. The result, a strong flush of fleabane that competed with the beans throughout the growing season. This crop was treated with a preharvest burndown to help with harvestability, but many of the plants had already set seed.
Fleabane pressure in wheat under seeded with red clover
Other times it is a management decision. For example, in this wheatfield the customer was adamant about keeping his stand of red clover, so BuctrylM was sprayed instead of Infinity (2). Pair that with a thin wheat stand thanksto our tough fall in 2018 and have a recipe for a mess of fleabane.
Looking back,it is easy to say, well Infinity should have been applied to that field, thebenefits of red clover aren’t worth the loss suffered due to weed competition,however it is also easy to underestimate how large a weed seed bank can be.Hindsight is 20/20. A solution to this could have been applying Infinity in thefall to get ahead of some of the fall germinated fleabane however, springgerminated fleabane in this thin stand could have still caused a problem.
Sprayer miss in soybeans
A more innocent example I saw this year was an accidental “untreatedcheck” in a soybean field. You can see exactly where the sprayer missed and howopportunistic these weed species can be.
Almost all weeds are tougher to kill when they are largercompared to when they are smaller. There is a reason as to why many herbicidelabels specify to spray when weeds are young and actively growing. Of course, therewill be years where things do not go as planned and we can only work with what Mother Nature has given us, but we are equipped with many great solutions andwe can usually come up with a strategy.
Residual chemistry's are a great tool thatneed to be part of a tank mix with multiple modes of action. We can no longer expect glyphosate to carry us through an entire growing season. Contact your local AGRIS or Wanstead Farmers cropsales specialist to further discuss what could work for you and your farmingoperation.