2012: Changes in Cotton Weed Management Practices in Georgia Following the Development of Glyphosate-Resistant Palmer Amaranth Lynn M. Sosnoskie 1,2 and A. Stanley Culpepper 1 1 University of Georgia - Tifton 2 University of California - Davis

Distribution of GR Palmer amaranth Map credit: R. L. Nichols

Cotton producing regions in US Map credit:

Glyphosate-resistant cotton: Changes in weed management Shaner (2000) Pest Manage. Sci. 56: – Glyphosate use increasing in cotton – Concomitant decrease in: PS II inhibitors – diuron, fluometuron, prometryn DNAs – pendimethalin, trifluralin Arsenates – MSMA Carotenoid biosynthesis inhibitors - clomazone

Glyphosate-resistant cotton: Changes in weed management Young (2006) Weed Technol. 20: – Increase in glyphosate applications: 1/crop (1996) to 1.8/crop (2001) – Decreased use of fluometuron and trifluralin: Fluometuron % ( ) to 20-27% ( ) Trifluralin – 52-67% ( ) to 30-39% ( ) Glyphosate – 30-36% ( ) to 56-57% ( )

Objective: To determine if cotton weed management practices in Georgia have changed following the development of glyphosate-resistant Palmer amaranth

Survey development and administration Two surveys (growers and extension agents) Surveys were designed by the authors and reviewed by an expert committee consisting of: extension agents, University (UGA and other) research scientists, UGA rural sociologist, industry personnel Surveys were ‘identical’ except for the fact that the growers were asked (anonymously) about their individual farming practices and agents provided 3 rd party information about county-wide activities

Survey development and administration Final survey was 8 pages long, contained 19 questions, and was administered in person Survey sections: – Commodities/acreage – Herbicide use – Additional weed management practices Tillage, cultivation, hand-weeding – Weed problems Including the presence and severity of glyphosate-resistant Palmer amaranth BEFORE AFTER

Survey development and administration was sent to all Georgia extension agents with cotton responsibilities (2010) describing the survey and requesting that they and 3-5 ‘representative’ growers in their county participate in the process Grower qualifications: – Cotton production – Responsible for making (agricultural) decisions on their property – Did not work for a chemical manufacturer, distributor, of retailer, nor a seed company

County Data 2009 Georgia Farm Gate Value Report (AR-10-01) County *Cotton acresValue (Millions)Cotton rankTotal commodity rank Berrien21,804$ Candler9,000$ Grady22,403$ Irwin28,269$ Macon9,781$ Miller28,366$ Randolph7,229$ Seminole24,369$ Screven12,822$ Sumter17,697$ Taylor452$ Terrell15,466$ Tift18,820$ Thomas25,858$ Turner20,879$ Worth49,185$ * Extension agent from Colquitt County also returned a survey (54,010 acres, $42.1 Million, Rank = 2).

Total grower (n = 65) acres = 129,615 (12.6% of GA cotton) Total agent county (n = 10) acres = 246,034 (24% of GA cotton)

Commodities - example Grower Question 4: How many acres do you farm?____________________ Grower Question 5: What types of agricultural commodity groups do you produce on your farm? YesNoApproximate number of acres or number of heads, houses or ponds Row and forage crops___________________________ Poultry and eggs___________________________ Livestock and aquaculture___________________________ Forestry products___________________________ Vegetables___________________________ Ornamental horticulture___________________________ Other (Please describe) (Continued on next page)

Commodity composition of growers' farms

Herbicides - example Grower Question 9: What herbicides have you relied on for weed control in cotton before ( ) and after ( ) the development of glyphosate-resistant Palmer amaranth (pigweed)? On what percent of you row crop acreage have you used each product? PREPLANT and PREEMERGENCE (burndown (including early), applications made at or prior to planting, and applications made prior to cotton emergence): Before ( ): After ( ):Yes No Average % of Acres Roundup, Glyphomax, Touchdown, others___ ___ _________________ ___ ___ _________________ 2,4-D___ ___ _________________ ___ ___ _________________ Aim___ ___ _________________ ___ ___ _________________ Clarity___ ___ _________________ ___ ___ _________________ Valor SX___ ___ _________________ ___ ___ _________________ Direx, others___ ___ _________________ ___ ___ _________________ Firestorm, Parazone, Gramoxone Inteon ___ ___ _________________ ___ ___ _________________ (Continued on next page)

Herbicides - example Herbicides are not divided up/grouped by MOA, activity, selectivity Grouped by timing of application as expressed in Georgia Pest Management handbook ( 1. PREPLANT and PREEMERGENCE (burndown (including early), applications made at or prior to planting, and applications made prior to cotton emergence): 2. POSTEMERGENCE OVER-THE-TOP (following cotton emergence): 3. POSTEMERGENCE DIRECTED:

Growers: Pre-plant herbicides applied Percent (%) of acres treated * **

Agents: Pre-plant herbicides applied Percent (%) of acres treated * * *

Growers: Pre-plant*/PRE herbicides applied Percent (%) of acres treated * * * *

Agents: Pre-plant*/PRE herbicides applied Percent (%) of acres treated * * * *

PPI herbicides applied Percent (%) of acres treated GROWERS AGENTS *

Growers: POST herbicides applied Percent (%) of acres treated * * *

Agents: POST herbicides applied Percent (%) of acres treated * * *

Growers: PD herbicides applied Percent (%) of acres treated * * *

Agents: PD herbicides applied Percent (%) of acres treated * * * * *

Growers: Changes in glyphosate and glufosinate applications from to *

Agents: Changes in glyphosate and glufosinate applications from to *

Growers : Herbicide costs = $32.30/A : Herbicide costs = $62.50/A

Agents : Herbicide costs = $27.80/A : Herbicide costs = $68.00/A

Additional practices - example Grower Question 13: Have you ever hand-weeded cotton due to insufficient chemical or mechanical weed control before ( ) and after ( ) the development of glyphosate-resistant Palmer amaranth (pigweed)? Before ( ):After ( ):Yes No Average % of Acres ___ _________________________ ______________________ Grower Question 14: Please estimate the cost of hand-weeding in cotton before ( ) and after ( ) the development of glyphosate-resistant Palmer amaranth (pigweed). Before ( ):After ( ): ____________________________$/Acre___________________________$/Acre (Continued on next page)

Photo by A.C. York : 17% of growers hand-weeded 5% cotton acres at $2.40/A : 92% of growers hand-weeded 52% cotton acres at $23.70/A

Photo by A.C. York : According to agents, growers hand-weeded 3% cotton acres at $3.50/A : According to agents, growers hand-weeded 66% cotton acres at $21.70/A

Growers: Changes in tillage/planting practices from to

Agents: Changes in tillage/planting practices from to

In-row cultivation Growers: : 34.3% of cotton acres cultivated : 43.9% of cotton acres cultivated Agents: : 13.1% of cotton acres cultivated : 32.1% of cotton acres cultivated

Growers: Most troublesome weed* * Summed averages are greater than 100% because of multiple votes for most troublesome species/grower

Growers: 2 nd Most troublesome weed* * Summed averages are greater than 100% because of multiple votes for most troublesome species/grower

Agents: Most troublesome weed

Agents: 2 nd Most troublesome weed