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You Are Here Sunflower Magazine > Spartan and The Crop Injury Issue


Sunflower Magazine

Spartan and The Crop Injury Issue
March 2000

Editor’s Note: February’s issue of The Sunflower carried an article

addressing the availability of Spartan® herbicide for control of

broadleaf weeds in sunflower under a conservation tillage system. Most

of that article focused on the weed control efficacy provided by

Spartan, with some mention of crop safety issues. This month, we are

expanding the discussion regarding possible crop injury and steps

growers should consider to avoid it.



Taking advantage of Section 18 labels available in several states

last year, hundreds of producers applied Spartan for pre-emergence

broadleaf weed treatment in conservation tillage sunflower fields. The

consensus? Given sufficient moisture for activation, Spartan provided

good to excellent control of such problem weeds as kochia, pigweed and

Russian thistle.

Intermingled among the satisfaction, however, were some reports of

sunflower crop injury — e.g., stunting, chlorosis, a “rippling” effect

on leaves — attributed to Spartan. While the sunflower plants usually

recovered and went on to harvest without any apparent yield loss, there

were certain instances where the crop never seemed to fully catch up

following the early season injury.

Spartan will be available in at least eight states once again this

year under a Section 18 registration. The key to avoiding sunflower

injury from Spartan, university weed science specialists emphasize, is

to follow the label directions closely — particularly as they pertain to

rates used on differing soil types. Label application rates range from

0.094 to 0.25 pound active ingredient per acre (i.e., 2.0 to 5.33 ounces

of product). FMC Corporation, Spartan’s manufacturer, provides the

following general rate recommendations:

Coarse Soils — A 2.0- to 2.67-ounce rate if the organic matter is

less than 1.5 percent; a 2.67- to 3.0-ounce rate if OM is between 1.5

and 3.0 percent; and a 3.0- to 4.0-ounce rate if OM is greater than 3.0

percent. FMC does not recommend using Spartan on coarse (“sand”) soils

with less than 1.0 percent organic matter.

Medium to Fine Soils — Rate of 2.67 to 3.0 ounces if organic matter

is under 1.5 percent; 3.0 to 4.0 ounces if OM is between 1.5 and 3.0

percent; and a 4.0- to 5.33-ounce rate of Spartan if the organic matter

is above 3.0 percent.



Last year, Kansas State University researchers Curtis Thompson and

Alan Schlegel established Spartan trials at two western Kansas

locations. At one site (near Tribune in Greeley County), the tests took

place on a silt loam soil with pH varying from 7.4 to 8.3 and organic

matter from 1.2 to 1.7 percent. The second site (Stevens County)

contained sandier soils with a 1.6-percent organic matter and a 7.7 pH

level. Visual injury ratings were made at two and nine weeks after

treatment.

Thompson and Schlegel found that at the silt loam site, injury from

Spartan increased in accordance with soil pH and calcium. The most

injury occurred when soil pH was 8.0 or higher and when calcium levels

were above 5,000 ppm. Crop injury did not translate into yield loss,

however.

On the sandier Stevens County site, sunflower crop injury actually

occurred only with the 0.25-pound (5.33-ounce) high-end label rate of

Spartan. While injury in that instance was significant, again it did

not result in reduced sunflower yield.

North Dakota State University weed scientist Richard Zollinger

reported no sunflower injury problems in his 1999 trials with Spartan at

the 1x rate. There was injury (ranging from 12 to 30 percent) at the 2x

rate when Spartan was applied either preplant incorporated or as a

pre-emergence treatment, Zollinger indicates. There also was

herbicide-induced damage to seeds with the PPI treatment, he notes, with

the higher percentage of PPI injury occurring with small seeds, as

compared to their medium or large counterparts.

Sunflower has exhibited good safety to Spartan on medium- to

fine-textured soils with organic matter above three percent, Zollinger

states in his North Dakota weed control guide for 2000. “Crop injury

may occur on soils with low organic matter and soil pH greater than 8.0,

especially on calcareous outcropping,” he observes.

Like FMC, Zollinger does not advise using Spartan on coarse-textured

soils with an organic matter of less than one percent. “Poor growing

conditions at and following sunflower emergence; cold temperatures; soil

compaction; or a rate too high based on soil type and organic matter may

result in sunflower injury,” he points out.

In his work with Spartan, Kansas State University weed scientist

Phil Stahlman experienced sunflower stand reductions only when

higher-than-recommended rates were used. “There is some risk of crop

injury on high-pH, lower-organic soils,” he concurs, adding that he

would like to see additional research to further refine Spartan use

rates for these types of soils.

Stahlman does not favor the use of Spartan as a PPI treatment. He

feels there’s too great a risk of the herbicide coming into contact with

the sunflower seeds, thereby harming seed germination rates and crop

emergence. — Don Lilleboe



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