Tips for Pre-harvest Glyphosate and Desiccation


photo courtesy of
Lentils are the main crop that will get hit with Reglone (diquat) and I will touch on them first. Ideally the staging is so that the lowest third of the plant pods are rattling and the seed itself is hard and doesn’t split; the middle third of the plant will be hard and not juicy, but will split nicely into two halves; and, the top third will be full size but immature. This is also the proper stage for glyphosate timing. The MRL of glyphosate did get increased to 10PPM (same as peas) this year so you are able to use glyphosate if you wish.

Be aware glyphosate is NOT a desiccant. It will kill the plants, yes, but it does very little to increase dry-down rates like Reglone will. A glyphosate application still means you could have 10 to 14 days or more until the proper harvest timing, whereas a four to seven day dry-down is more typical from a Reglone application.

Proper staging for Reglone/glyphosate on pea is when the bottom third of the pods have detached seeds so the pods rattle, and the pods are translucent and shrunken. The middle third of the plant will have shrunken and leathery pods and will split when squeezed — the upper third will just be starting to turn. Again, glyphosate is not a desiccant and will only speed up harvest by a few days or so vs. no glyphosate.

When it comes to using Heat (saflufenacil from BASF) there is no MRL set and I would suggest to avoid using it if you can to save yourselves from having to deal with a buyer denying your lentil crop. If you do decide to use Heat be aware that it will not be as effective as Reglone, at least not in my experience. You also must use an increased rate as opposed to the 10.4g/ac (80ac/jug). You should use at least 14g/ac and ideally use upwards of 20 grams per acre (40ac/jug) to see better results. Aim (Carfentrazone) from Nufarm is also registered as a desiccant. You have to increase the rate significantly to get the dry-down results you want. In my experience it is a product that will still get the job done if you decide to go this way.

For wheat and barley (not destined for malt) timing of a pre-harvest application of glyphosate, coincides with swath timing. The wheat and barley will be at 30% to 35% moisture, or hard dough stage. A finger nail imprint will remain on the seed. You can get away with maybe two to three days before typical swath timing, but remember if you go in to early with glyphosate the seeds will appear shrunken and it will have a similar appearance to frost damage. In wheat you may also look at the peduncle (the stem located just below the head) and it will have turned from green to a brown colour.

Remember glyphosate is much better than a desiccant on perennials so if you have a field with lots of quackgrass, Canada thistle, etc., then using glyphosate is your best route to go. Don’t tank mix, but if you want to get the best of both worlds use glyphosate first and then Reglone three days later to get dry down and good perennial weed control.

Some notes on Reglone:

-Reglone prefers water pH of <7 -Ideally use 15-20 gallons of water per acre, the more the better. -Doubling up on surfactant can be very effective to ensure chemical penetration into the plant. -Be sure to increase PSI to above 50 -I have heard mixed comments on nozzles, Twin TurboJet seem to be a good option though. -LI700 is a surfactant that helps get the chemical into the plant as well as lower pH, and I've seen good results with it. Rate is 0.1% v/v, 0.2 if you want to double the rate. If you are using an AgSurf product, for example, then it is recommended you double it. -Reglone is a contact product that reacts off UV light so spraying in the evening and allowing the chemical to get into the plant is a very effective route to go. This means it is fully soaked into the plant for the next morning/day. You may get some slight local systemic effect vs. straight contact as well if sprayed at night due to it soaking in a bit better within the leaves. It is also very rainfast — about 15 minutes. -Reglone prefers hot temperatures so if you can time it so that you spray in the evening and the next day is HOT, it will be more effective. -Reglone is a group 22, this can be an effective chemical to change up herbicide groups in your rotation. -The rate is 0.7-0.8L/ac typically, but some farmers go 1L/ac. My main tip with the rate is don’t assume that since you are going the high rate you can cut the water volume. In my experience going the lower rate with higher water volume is MUCH better than going high rate with a low water volume. Visit Shane’s Blog.

Sources: Syngenta Canada

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