By Brian Hefty

This may seem crazy to you, but glyphosate has been in short supply for several weeks.  Monsanto and Dow have both had allocation programs since mid-June.  The reason why product is so tight is due primarily to 2 factors: higher use rates and an early spring.

Most farmers have bumped the standard rate of glyphosate from 32 oz. to 48 oz. on a 4# basis.  In fact, we find many farmers using 64 oz. on a 4# basis because glyphosate is so inexpensive, and it seems like it takes more product every year to control the same weeds.

When the weather got unseasonably warm early this spring, weeds got an early jump on things, meaning farmers across the country were forced to make an extra herbicide application.  Even in conventional-till fields in the Midwest, we saw glyphosate being used pre-emerge.  That just doesn’t happen in a normal year.

Anyway, the companies are really struggling to catch up, and there is a nationwide shortage of glyphosate right now.  Here is my advice to you in terms of glyphosate and spraying your post-harvest burndown.

  1. Get your glyphosate bought now.  The longer you wait, the higher the price will be and the less chance you’ll have product when you want to spray.
  2. Use a tankmix partner when you spray.  Banvel is the most popular product to add in because it is highly effective on almost all broadleaf weeds, and it is very inexpensive.  Plus, if you use the 1 pint per acre rate, you will get a little bit of residual control.  Since 2,4-D has gone up so much in price over the last couple of years, Banvel is now less expensive rate for rate.  On our farm, we have used a 1 quart per acre rate of Banvel in the fall post-harvest to eliminate dandelions and marestail prior to planting corn or wheat the next spring.  Yes, this costs about $10 per acre at that high rate, but it’s the best option to wipe out those tough weeds.
  3. If you are planting a fall crop, make sure you have eliminated the green bridge.  In order to help prevent the spread of disease and insects to your next crop, your land needs to have no green growth on it for a full 2 weeks prior to seeding.  It is a lot less expensive to control weeds now rather than to try to stop diseases and insects in your next crop.  More importantly, you’ll get higher yields if you eliminate the green bridge.
  4. Use the right adjuvants.  Depending on the tankmix partner you use, you may need crop oil or nonionic surfactant with your herbicide.  Keep in mind that weeds are often more difficult to control late in the summer.  After the weather has been hot and dry for a while, leaf cuticles get thick, meaning they are harder to penetrate with herbicide.  With a Roundup/Banvel mix, use 17 pounds of ammonium sulfate (AMS) per 100 gallons of water.  True AMS, in our experience, is better than any of the AMS-replacement products.  Plus, you get a little exercise carrying a few 51# bags each day.  In addition to the AMS, you can add 1 to 2 quarts of nonionic surfactant (NIS) per 100 gallons of water.  This isn’t a requirement, but it could help keep your spray on the leaves and penetrate them slightly better.  Many farmers take this step, as they have seen slightly improved results.
  5. Don’t use too much water.  Keeping droplets concentrated, especially when leaf cuticles are thicker and waxier in the late summer is key.  There are a few people that will tell you to bump your water rate to 15 or 20 gallons per acre, but never use more than 10 gallons of water per acre when spraying a glyphosate product.  Excess water means more of your product ends up on the ground rather than in your weeds.

A post-harvest burndown is very important if you want to keep your weed seed bank low, as well as reduce the likelihood of future disease and insect problems.  While glyphosate is still important in burndown situations, be sure to add a tankmix partner for residual control and activity on glyphosate-resistant (or tolerant) weeds.