NDSU Crop and Pest Report
Weeds


ISSUE 4  May 23, 2002

 

2002 PULSE CROP HERBICIDE OPTIONS

Field pea, lentil, and chickpea generally are poor competitors with weeds. Weeds should be controlled early (by one to three weeks after crop emergence) to minimize risk of reduced pulse crop seed yield and quality. Use integrated weed management strategies including cultural, mechanical, and chemical options. The following list displays the currently-labeled (May 2002) herbicides available for use in pulse crops.

Herbicides labeled for field pea:

Herbicides labeled for lentil:

Herbicides labeled for chickpea:

 

WEED CONTROL IN CHICKPEA

(Adapted from Montana State University publication "Growing Chickpea in the northern Great Plains" at: http://www.montana.edu/wwwpb/pubs/mt200204.html  .)

Spartan will control troublesome broadleaf weeds like kochia and Russian thistle in no-till chickpea. NDSU research has shown that higher rates of Spartan may be required to control wild buckwheat. Spartan can be applied up to 30 days prior to planting to 3 days after planting. A burndown herbicide like glyphosate may be tank mixed with Spartan if broadleaf or grass weeds have emerged. For optimum activity, Spartan needs a minimum of 0.5 to 0.75 inches of moisture after application to become activated in the soil. Soil factors such as pH, texture, and organic matter content affect Spartan activity in soils. Carefully consult the label to determine optimum rates for your farm.

In conventional tillage systems, Treflan, Sonalan, and Prowl applied preplant incorporated will control certain broadleaf weeds plus foxtail and barnyardgrass, but not wild oat or quackgrass. Pursuit can be applied preplant incorporated or preemergence to control certain broadleaf and grass weeds. However, Pursuit will not control ALS-resistant kochia and the user assumes all risk of crop injury.

Tough is the only POST herbicide labeled in chickpea that will control broadleaf weeds. Under optimum conditions, Tough will control kochia, pigweed, lambsquarters, and Russian thistle. Tough will not control wild buckwheat. For optimum weed control, Tough should be applied in a high spray volume (20 gpa), in warm, sunny conditions, and to weeds 3-inches tall or less. Tough should not be applied under cool, cloudy conditions.

 

NEWLY-LABELED HERBICIDES FOR USE IN 2002 ON FIELD PEA

Refer to herbicide labels and the North Dakota State University Extension Service circular W-253 ‘2002 North Dakota Weed Control Guide’ for required details on herbicide use. Also, note that crop rotation restrictions exist for several pulse herbicides including Pursuit, Raptor, Sencor, Spartan, and trifluralin. Get answers to your specific pulse weed management questions by contacting NDSU crop specialists or extension agents.

Gregory Endres
NDSU Extension Service Area Agronomist
Carrington R&E Center

Brian Jenks
NDSU Weed Scientist
North Central R&E Center, Minot

 

SECTION 18 FOR SPARTAN

Spartan received a Section 18 registration in 2002 for weed control in field pea, sunflower and flax. The cold weather has delay emergence of these crops while Spartan has been applied on much the acreage. There is concern and questions about amount of rainfall needed to activate Spartan before weed emergence. Information in ND Weed Guide suggests 0.75 inches of precipitation is needed to activate Spartan. Below is information which will help answer some of those concerns.

When activated by rainfall, Spartan provides 8 to 10 weeks controls of annual small-seeded broadleaf weeds including kochia, pigweed spp., common lambsquarters, nightshade spp. and biennial wormwood. Spartan rate ranges from 2.67 to 5.33 oz product/A should be based on soil texture and organic matter. The lower rates are for light soils with organic matter less than 3% and the higher rates are for heavy, clay soils with greater than 3% organic matter. However, Spartan becomes much more soluble and active as pH increases and as soil organic matter and clay content decreases. Spartan may be applied up to 30 days prior to planting but the rate should be increased for this early application. Spartan can be applied and incorporated before planting and also preemergence after the crop is seeded. SPARTAN SHOULD NEVER BE DEEP INCORPORATED! Keep any incorporation shallow, keeping Spartan concentrated in the upper 1 inch of soil. Deep incorporation dilutes the herbicide and reduces weed control. This limits applying Spartan with Treflan, Sonalan, and Prowl which require deep incorporation.

NDSU research has shown excellent weed control from Spartan in many environments but the best weed control results when 0.75 inch of rain occurs before weeds emerge. In high pH soils where Spartan solubility is much higher, adequate activation may occur where less than 0.75 inches of rain has accumulated. Less than 0.75 inch of rain will partially activate Spartan and should control more easily controlled weeds like pigweed, kochia, and nightshade but more difficult weeds, like marshelder and wild buckwheat will not be controlled. Under limited moisture conditions, a light harrowing with a spike-tooth harrow may improve control of some weeds but will not substitute for rain.

Ideally, the rain needed for activation will occur shortly after Spartan is applied and prior to weed emergence. Spartan is not susceptible to photodecomposition or volatility following application to soil so the Spartan will wait for a rain and become active after the rain. However, weeds that emerge prior to the activating rain probably will not be controlled. Spartan has a relatively long soil residual and will give 8 to 10 weeks of weed control. Recommended rotation intervals should be observed for crops that follow Spartan to avoid damage from carryover.

Crop injury from Spartan would not be expected in cool and dry conditions since the Spartan would not be activated by rain. However, cool conditions following and activating rainfall may increase crop injury as compared to good growing conditions because cool temperatures will slow crop emergence and increase the time of exposure of the emerging crop to the herbicide.

Alan Dexter
Extension Sugarbeet Weed Specialist
adexter@ndsuext.nodak.edu

Richard Zollinger
NDSU Extension Weed Specialist
rzolling@ndsuext.nodak.edu


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