Is It Too Late… or Too Early to Spray?

A brief write up by our Crop Input Specialist, Zach Machura, clarifying when and what can be spayed this fall for desiccation and insect control.

Desiccation: An excellent way to accelerate crop dry-down and speed up harvest. What would we do without desiccation?... First of all it is important to realize exactly what desiccation is. We all know that desiccating can help you get into the field to combine much faster; however, it is also important to realize that all a desiccant does is dry down the crop, maturity has to come on its own. Because of this crucial misunderstanding farmers often desiccate too early, which results in shrunken seeds and locked in green seed.

There is a bit of a belief with wheat that as long as the straw is cured the head can still be green, you can desiccate with Roundup, and you’ll combine two weeks later. You might combine two weeks later and the grain quality may have a small chance of being passable but this is far from acceptable. It is important to know that there is only a small handful of herbicides registered as desiccants (i.e. Reglone Ion and Heat LQ). Registered desiccants like these are the only products that can be sprayed shortly before harvest (3-4 days) and or when the crop has a high moisture content (>30%).

Roundup has never been registered as a desiccant. Roundup is registered for weed control within close proximity of harvest. Roundup is, however, subject to residue limits, stage restrictions, and pre-harvest intervals just like other in-crop chemicals. As a result Roundup should only be applied when the crop is below 30% moisture (or when the seed stays dented after you put you put your thumbnail in it) and at the very least 7 days before harvest if not 14. The reason why it is so important to do this is that a seed over 30% moisture will readily absorb glyphosate which leads to increased amounts of residue in the grain which do not decline. The reason why you would wait 7 or more days before harvesting is due to the fact that the levels of glyphosate on the outside of the seed need time to decrease. Grain that has high glyphosate residue can be difficult to sell and can even jeopardize the market. Major grain buying countries such as China have been getting more and more apprehensive about residue within crops and there is even a quiet murmur of residue limits being decreased in the coming years to half or even zero. Just think about a world without pre-harvest Roundup. With trade relations around the world growing more and more fragile it is even more important to considering the impact of the timing and herbicide that you use to dry down your crops.


Insect Pest Control:

In our area we are starting to get a greater variety of, and more outbreaks of, crop damaging insects such as Bertha Armyworms and Grasshoppers. An important thing to remember is that if left untreated, in time, population densities of insects will come into check from natural predators.  We need to understand when spraying an insecticide we also kill the natural predators to the pest species; which creates a climate where we are continuously susceptible to insect outbreaks. This being said I understand that producers also need to make a profit so it is hard to let a crop be destroyed by insects. But, remember the application of insecticide is only beneficial if the cost of the insect damage will exceed the cost of applying an insecticide including the application costs. These expenses exist whether you own a sprayer or not. This magic number known as the economic threshold for control. This threshold can be easily found using the price of grain and the cost of application and referencing the two together on a chart for the specific pest (these charts can be found from sources such as the Canola Council). If you have found that an insect has exceeded the economic threshold at this time of year the next thing to consider is the pre-harvest interval for the crop.

Both Decis and Matador have a pre-harvest interval of 30-40 days in cereals which means at this time of the year don’t even think of it. (As much as you’d like to take a pot shot at those grasshoppers).

Trying to tackle Bertha Armyworms in Canola? Decis and Matador both have a pre-harvest interval of 7 days in Canola. Exactly what harvest is with these insecticides is a loose term, swathing can in fact cause insecticides to become encapsulated. This means their levels do not drop off quite as fast (due to the decreased airflow in the swath).

In summary, when debating a late herbicide application, pondering desiccation or arming up to control insects, remember managing residues is vital for being able to sell grain. So please pay close attention to your Pre-Harvest intervals. If you ever have any questions please contact our team or reference the product label.

Link to August 30th Newsletter Here.