Kevin B. Kelley and Lloyd C. Haderlie

AgraServ, Inc., American Falls, ID

AminopyralidAuxinic herbicide labeled for use on

rangeland, permanent grass pastures, CRP land, non-cropland areas, and natural areas.

Very active on several annual and perennial broadleaf weeds, including Canada thistle.

Known to pass through animals that consume treated forage and be present in manure and urine similar to picloram.

Shorter soil half-life than picloram.

Aminopyralid Injury to PotatoesResearch Prompted by Farmer ComplaintsAerial applications of aminopyralid to

range/pasture in 2008Potatoes bordering pasture in 2008 and 2009

showed injury symptoms and yield lossWeeds sensitive to aminopyralid in potato

fields didn’t show injuryLaboratory analysis of potato foliage and

tubers resulted in positive detection of aminopyralid

Aminopyralid Affect on PotatoesPersistence in the soil?Potato sensitivity?

Growth stage differences?Daughter tuber response?

Methods - TimingFall Soil Carryover

Applied Nov. 7, 2009Spring Preplant

Applied May 18, 2010 – One day before plantingIn Season

Early – Applied 2 weeks after emergenceMid-Season – Applied late July near row closure

Daughter Tuber Plant ResponseApplied Aug. 31, 2009Treated tubers planted May 2010Known to be a very sensitive assay for picloram

Methods - RatesAminopyralid – Use rate range - 53 to 123 g

ai/haapplied from 44 g ai/ha (~50%) down to 0.044

g ai/ha (0.05%)Picloram – Average use rate - 280 g ai/ha

applied at 4.4 and 44 g ai/haClopyralid – Max use rate of 280 g ai/ha

applied at 26 or 280 g ai/haDicamba – Average use rate of 560 g ai/ha

applied at 56 or 560 g ai/ha

Fall Soil CarryoverPotato Injury July 16th

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LSD – 4 (P=0.1)

Perc

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jury

Aminopyralid – g ai/ha

Fall Soil CarryoverTotal Potato Yield

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LSD – 41 (P=0.1)Aminopyralid – g ai/ha

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Fall Soil CarryoverUS #1 Potato Yield

LSD – 37 (P=0.1)Aminopyralid – g ai/ha

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Spring Preplant AppliedPotato Injury Aug 10th

LSD – 17 (P=0.1)Rates in g ai/ha

Aminopyralid

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jury

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Spring Preplant AppliedTotal Potato Yield

LSD – 78 (P=0.1)Rates in g ai/ha

Aminopyralid

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Acr

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In-Season Applied Potato Injury Aug 10th (6 or 2 WAA)

LSD – 6 (P=0.1)Rates in g ai/ha

Aminopyralid Aminopyralid

Two Weeks After Emergence Near Row Closure

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jury

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In-Season AppliedUS #1 Potato Yield

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Acr

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LSD – 71 (P=0.1)Rates in g ai/ha

Aminopyralid Aminopyralid

Two Weeks After Emergence Near Row Closure

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Daughter Tuber Plant Response - Potato Injury Aug 10, 2010 (Sprayed 2009)

LSD – 9 (P=0.1)Aminopyralid – g ai/ha

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jury

Daughter Tuber Plant Response – Total Potato Yield (Sprayed 2009)

LSD – 67 (P=0.1)Aminopyralid – g ai/ha

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Acr

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SummaryAminopyralid injured potatoes and reduced yield

and quality following all scenarios tested including fall applied to soil.

Injury levels were similar to or exceeded that caused by picloram

Greater rates of dicamba or clopyralid were required to cause potato injury.

Potatoes appear to be especially sensitive to aminopyralid.

All potatoes were saved for seed grow out in 2011.

Questions?