Reduce Desiccant Drift to Prevent Injury to Sensitive Crops

Prepared by Vikram Bisht, MAFRI MAFRI Plant Pathologist – Horticultural Crops

Wheat and other crops are now being desiccated with glyphosate. It is important to watch out for the neighbouring crops, especially seed crops. Drift of glyphosate can affect seed performance in the next spring.

 Potatoes, for example, are very sensitive to glyphosate drift.  Field demonstration plots in Portage and Winkler sites, the drift on to potatoes early in the season showed symptoms on the leaves of young plants; but late in the season the potatoes plants are so large, that they do not show much sign of injury.  However, in the next season the seed emergence is significantly reduced or slowed.  There are reports from US and Canada, of expensive lawsuits due to injury to seed potatoes.

 Use of low drift nozzles, larger droplet size by reducing sprayer pressure, use of drift reducing adjuvants, keeping in mind the wind speed and direction at time of spray – could help reduce the injury to neighbouring non-target crops.

CROP CHATTER-Prevent Herbicide Drift Injury

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Swath, Desiccate or Let it Be – Field Peas & Cereals?!?

Prepared by Anastasia Kubinec, MAFRI Oilseed Specialist & Pam deRocquigny, MAFRI Cereal Specialist

With the cool, damp weather, crops are not maturing as fast as we would like.  ‘Stagey’ crops, big weeds (ragweed, buckwheat, kochia, redroot pigweed) and risks of weathering impacting quality have resulted in many calls about the differences/benefits of swathing, desiccating or letting the crop be.

First, go look at the crop again – how many stages is the crop at? Is it just low spots that have not turned? If the crop is starting to even up, you may want to leave it with the warmer temperatures coming this week (August 12-19, 2013) and let nature work for you. If the crop is at multiple stages and there are big weeds that will cause combine plugging, swathing, desiccating or pre-harvest weed control is a good management option.  For specific product information, contact the marketing companies for rates and registration details.

Key Notes:

  1.  Swathing or desiccating earlier than recommend (30% seed moisture) will not shorten the maturity of the seed. That is based on genetics and weather.  Performing these activities too early will result in reduced seed yield and quality.
  2. Glyphosate is not a desiccant- it is a pre-harvest herbicide and kills crops and weeds.  Use it for perennial weed control and not to desiccate the crop. Don’t use if crop is for seed use.
  3. Some product MRLs (Maximum Residue Limits) have not been set or are lower than what we can meet for crop export into other countries.  Be aware of marketing restrictions that may arise from using certain desiccants/harvest management tools.  For pulses see  For other crops, talk to you buyers.
  4. Know the weather conditions at application timing that will give the best results – Reglone works better on senescing plants and when temperatures are warm, Glyphosate works better on actively growing plants.

Field pea –Swath when most of the vines/pods are yellow-tan color and you can only barely leave a thumbnail impression. Desiccate when bottom 75% of pods are yellow with seeds firm and rattling in pods.  Desiccation usually eliminates the need for swathing and avoids the issues of wind-blown or rain-soaked swaths, and pick-up losses.  Decision to swath or desiccate will be based on weather forecast for the next 10 days, experience and machinery available.

Winter/Spring Wheat – Swathing timing and desiccation timing is the same – seed at 30% to 35% moisture, or hard dough stage (thumbnail imprint can barely be left in seed). Reglone and HEAT are not registered on any cereal crops for pre-harvest use.  If crop is intended for seed, using  glyphosate is not an option, so swath.  If not for seed and the weather forecast calls for wet conditions for the 10 days, glyphosate may be preferred versus swathing as the crop will weather better standing than in a swath.

Barley/Oat – Check  with your buyer about their policy on desiccants on the crop.  This may make the decision for you.  After determining this, the timing of swathing/desiccant is the same as wheat and the considerations to swath or desiccate are applicable as well.

For malting barley, maltsters want plump, mature kernels. The crop must not be swathed on the green side. Delay swathing until the heads have lost their green colour and have a moisture content of <30%. Swath around green patches to avoid having the sample from the field turned down because of green or immature kernels.   Keep in mind that wet weather may loosen the hull, reducing quality. Straight combining is becoming popular. Standing malt barley suffers less damage from moisture and dries faster. However, this benefit must be balanced against the increased risk of shattering losses. Six-row barley is more prone to shattering and neck-break than two-row barley.


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Should I Still Desiccate My Sunflowers or Has the Frost Done it For Me?


A killing frost in sunflowers is considered to be –4C to –5C for 6 or more hours.

Although we have had a frost, we have not experienced a killing frost yet in Manitoba.  So, the current cold nights have not been cold enough to substitute for a desiccation.

A desiccant may still be considered, if no other frost is is the forecast, but as we have now gotten cooler, plant metabolism has slowed down. The plants are not metabolizing the harvest aid desiccant products as quickly and dry-down will take longer.

To optimize the benefits of applying a desiccant, it is necessary to look at the weather forecast for the next week.

How cold will it get? If a frost below –4C is expected, a desiccant might not be required

How warm will it get? Desiccants perform much better if applied in temperatures >20 C

Applications to healthy green plants will provide optimum results. Since we have had a lack of morning dew lately, it is extremely important of maintain water volumes to get proper coverage.

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