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Frequently Asked Questions
- Herbicide Options to Enhance Harvesting
Which
glyphosate products are registered for pre-harvest application?Crops
registered and rates (per acre)
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Product
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Barley*,
Bean (dry), Canola, Field Pea, Flax (including Solin), Lentil, Oat*,Chickpea**,
Soybean, Wheat
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Oat
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Forages
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Credit, Factor, Glyfos,
Maverick, Renegade, Roundup Original, Roundup Transorb, Touchdown iQ,
Vantage, Vantage Plus
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1.0 L
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1.0 L
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1.0 –
2.0 L
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Roundup Dry
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0.53
kg
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0.53
kg
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0.53
- 1.06 kg
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Renegade HC, Roundup
Ultra, Roundup WeatherMax
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0.67
L
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0.67
L
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0.67
- 1.34 L
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Do not apply to crops grown
for seed.
*Registered for application
to barley grown for malt and tame oat grown for milling. Contact malt barley
or milling oat buyers prior to application to confirm acceptance of glyphosate-treated
grain.
**Roundup WeatherMax
only
What types
of actions do these herbicides accomplish?
Glyphosate products are
registered to be used prior to harvest, specifically for the purpose of killing
perennial weeds. Glyphosate works systemically upon absorption by the plant’s
foliar tissue.
Which
weeds are controlled by pre-harvest applications of glyphosate?
- Quack grass - four to
five green leaves.
- Canada thistle and perennial
sow-thistle - bud stage or beyond.
- Common milkweed - bud
to bloom stage.
- Toadflax - bud to full
bloom stage.
- Dandelion - from rosette
to full bloom stage.
How much
water do I use when applying glyphosate in this application?
To ensure good coverage
of weeds and to help penetrate crop canopy, a minimum of 23
L/ac. (5 gal./ac.) is recommended. For heavier canopies, or high weed densities,
use 45 L/ac.(10 gal./ac.).
Is the timing
of application important?
Applications of glyphosate
should be made when grain moisture is less than 30 per cent (does not apply
to forage). The following chart can be used as a guideline to help determine
when 30 per cent grain moisture has been reached.
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CROP*
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VISUAL SYMPTOMS
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Wheat, Barley, Oat
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Hard dough stage –
a thumbnail impression remains on the seed.
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Canola
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Pods are green to
yellow, and most seeds are yellow to brown.
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Flax (including Solin)
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Majority of the bolls,
75 to 80 per cent, are brown.
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Lentil
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Lowermost pods (bottom
15 per cent) are brown and rattle when shaken.
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Pea
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Majority of the pods,
75 to 80 per cent, are brown.
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Chickpea
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Thirty per cent or
less grain moisture. Stems are green to brown in colour; pods are mature
(yellow to brown in colour); 80 to 90 per cent leaf drop (original leaves.)
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Soybean
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Stems are green to
brown in colour, and pod tissue is brown and dry in appearance (80 to
90 per cent leaf drop.)
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Dry Bean
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Stems are green to
brown in colour, and pods are mature (yellow to brown), and 80 to 90 per
cent of the original leaves have dropped.
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Forage
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Three to seven days
prior to the last cut before rotation for forage renovation. Do not apply
to forage stands that are to be maintained.
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*See the crops section of
the 2006 Guide to Crop Protection for a guide to the products registered on
each crop.
What
is a pre-harvest interval?
The pre-harvest interval
is the number of days that must pass between the last application of a pesticide
and harvest. Harvest is the cutting of the crop, or removal of the produce
from the plant. It includes direct-combining, cutting (swathing), or grazing.
It does not include swath-combining or baling for hay.
What is
the pre-harvest interval following glyphosate application?
To allow the herbicide to
work, allow three days or 72 hours before swathing to allow for weed control.
The crop may be harvested (straight cutting or swath pickup) seven days after
application. Thorough weed dry down usually occurs in 10 to 14 days following
application.
How does
a true desiccant work?
Desiccants work by contact
on plant foliar tissue. The action dries immature green material at the top
of indeterminate crops and green weeds to facilitate harvest. Application of
a desiccant does not facilitate quicker maturation of the crop.
What
products are registered desiccants in Canada?
Two products are registered
for the explicit purpose of desiccating crops: Reglone Desiccant, and Liberty.
Which crops
are registered for application with Reglone?
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CROP
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STAGE
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RATE
(L/AC.)
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Dry beans, soybeans
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Crop has lost 80 to
90 per cent of its leaves and 80 per cent of the pods are yellow.
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Ground
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Aerial
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Flax, Solin
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75 per cent of the
bolls are brown.
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0.5 to
.7 L
(Use
high rate for dense crop, heavy weed infestations)
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0.7 to
0.9 L
(use
high rate for dense crop, heavy weed infestations)
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Lentils
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Lowest pods are light
brown, and rattle when shaken.
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Mustard
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75 per cent of the
seed has turned brown.
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Canola*
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60 to 75 per cent
of the seed has turned brown.
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Peas
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Bottom pods are ripe
and dry; seeds are detached from the pods.
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Chickpeas**
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Plants are yellow,
pods mature, seeds changed colour and detached from pods.
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Sunflowers
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Backs of sunflower
heads and bracts are turning yellow and seed moisture is 20 to 50 per
cent.
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Potatoes (some top
growth and / or some weeds
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Two weeks prior to
harvest.
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0.7 to
0.9 L
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Two applications
are required.
First
application
0.7 to
0.9 L/ac.***
Second
application (four to five days later) at 0.5 L/ac.
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Potatoes (dense crop,
heavy weed infestations)
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1.4 L
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Alfalfa, bird’s-foot
trefoil, red and white clover (for seed production only).****
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Pods are ripe but
before shattering. Harvest within 7 days.
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0.7 to
1.L
(use
high rates for dense crops, heavy weed infestations)
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0.7 to
1.L
(use
high rates for dense crops, heavy weed infestations)
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* This product can cause
shattering losses in canola. It should only be used on Argentine canola to
assist in the harvest of a severely lodged crop.
** Aerial applications
to chickpea – 0.7 L/ac. only.
*** Use of high rate
for dense or immature vines.
****Do not use on
forage legumes that have been treated with a residual herbicide in the previous
12 months.
Water Volumes: 91
to 222 L/ac.(ground); 222 to 445 L/ac. on potatoes (ground); 18 L/ac. (aerial);
use the highest water volumes when crop canopy is heavy or if weed growth is
dense.
How long
do I wait before harvesting following Reglone desiccant application?
Pre-harvest interval:
Wait four to seven days before harvesting lentil. Do not exceed seven days
to harvest when treating forage legumes. Wait at least seven days before harvesting
lupins. Wait seven to 10 days before combining canola and mustard, but do not
wait longer than 14 days. Wait 15 to 20 days for sunflowers. Harvest flax
and peas when sample tests dry.
How do
I use Liberty desiccant?
- Alfalfa (seed production
only) – 50 to 75 per cent pod turn (brown) – 1.09 L/ac.
- Lentils* - 40 to 60 per
cent pod turn (yellow to brown) – 0.81 to 1.09 L/ac.
- Potatoes* - 14 to 21
days prior to harvest - 1.21 L/ac.
- *Not for crops grown
for seed production.
- Water Volumes: 45 L/ac.
(ground) and 13 to 22 L/ac. (aerial).
What is
the Pre-harvest interval for Liberty?
Do not harvest desiccated
potato or lentil crops within nine days of treatment.
More
information can be found at these Internet websites:
Or contact:
- Saskatchewan Agriculture
and Food’s Agriculture Knowledge Centre at 1-866-457-2377
Acknowledgements:
- Dale Risula, PAg, SAF,
Integrated Cropping Management Systems Specialist
- Ray McVicar, PAg, SAF,
Crop Production Specialist
- Grant McLean, PAg, SAF,
Crop Management Specialist
- Dr. Patrick Mooleki,
SAF, Crop Development Specialist
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