Dr. Eric P. Prostko Extension Weed Specialist Dept. Crop & Soil Sciences University of Georgia December Weed Control Update (Peanut, Field Corn, Soybeans, Sunflowers)

Peanuts t Spartan t Cobra t newer metolachlor formulations t Valor Issues t others issues

Spartan in Peanut t Labeled in not in FL t 4F formulation t 4.8 to 8.0 ozs/A t soil-applied t broadleaf weed control t nutsedge t cotton rotation concerns t crop injury on lighter soils t PPO inhibitor

Spartan Rotation Restrictions

Spartan Injury

Cobra in Peanut t Labeled in Fall 2004 t postemergence 36 leaf peanut 390 day PHI t 12.5 ozs/A t broadleaf weed control t a hotter Blazer t tank-mixes with Basagran, Cadre, Pursuit, Select, 2,4- DB t PPO inhibitor

Metolachlor Mysteries? t 9 formulations in marketplace t new metolachlors (88% s + 12% r) 3Dual Magnum, Dual II Magnum (Syngenta) 3Cinch (DuPont) t old metolachlors (50% s + 50% r) 3Stalwart, Stalwart C (Sipcam) 3Me-Too-Lachlor, Me-Too-Lachlor II (Drexel) 3 Parallel PCS, Parallel (Makhteshim-Agan)

Metolachlor Prices *only labeled for use in field corn and popcorn

Tropical Spiderwort

Tropical Spiderwort Response to Dual Magnum and Stalwart, Grady Co., I Applied PRE at 1 pt/A. *

Tropical Spiderwort Response to Dual Magnum and Stalwart, Grady Co., II Applied POST at 1 pt/A with glyphosate to 3” tall COMBE. *

Valor Issues: Is that hose clean? Tank/Line RinsateLine in Glyphosate

Valor and Sprayer Cleanup

Which plot had AMS? Which plot had AMS? (Both had Cadre at 1.44 ozs/A + 1% v/v applied 24 DAP) PE July 1, DAT

Which plot had AMS? PE August 3, DAT

Field Corn t Option vs. Accent t RR corn issues 3glyphosate timings

Field Corn Option vs. Accent t POST grass control t except crabgrass t OP/SU interaction t roughly same cost/A t 2004 Option was less effective than Accent

Texas Panicum Control - I Accent vs Option CN (Ponder Farm) Applied 22 DAP PANTE = 1”, 3-4 leaf a a abc bcd b cc d

Texas Panicum Control - II Accent vs Option CN (Attapulgus) Applied 21 DAP PANTE = 1-2”, 2-4 leaf ab b a b a b a b

Texas Panicum Control - III Accent vs Option CN (Attapulgus) Applied 21 DAP PANTE = 1-2”, 3-4 leaf ab abc a ab a bcd

Texas Panicum Control (104 DAT) - II Accent vs Option CN (Attapulgus) Applied 21 DAP PANTE = 1-2”, 2-4 leaf Untreated 0.67 ozs/A 1% v/v 1.5 ozs/A 1.25% v/v 3 lbs/A

Conventional or RR Systems?

Are the RR hybrids any good? CN b b a aa a a

Use Rates for Glyphosate in RR Corn

Soybeans t Nutsedge control in RR beans t RR cotton in RR soybeans t Mn tank-mixes t Sequence t tropical spiderwort t glyphosate timings

Nutsedge Management in RR Soybeans t split applications of glyphosate 3better on purple than yellow t tank-mix with Classic 3controls yellow suppresses purple t tank-mix with Pursuit 3better on purple than yellow 3 rotations/cost

Controlling RR Cotton in RR Soybeans t Canopy - PRE 3metribuzin + chlorimuron 38 ozs/A t POST glyphosate tank- mixes 3Resource (4 ozs/A) 3Reflex (12 ozs/A) 3Classic (0.33 ozs/A) t need PRE fb POST to be most effective

Glyphosate/Manganese Tank-Mixes t research from VA has shown that Mn will reduce weed control when tank-mixed with glyphosate 3 9 to 38% reductions depending upon species t Mn not a problem with Blazer, Classic, Pursuit, or Basagran. Sources: Bailey et al., 2002 (Weed Technology 16: ) and Heckman et al., 1999 (Journal of Production Agriculture 12: )

Sequence for Weed Control in RR Soybeans t label in October 2004 t mixture of glyphosate -K + Dual Magnum t pts/A 3$/15-18/A ae ai (2.5 pts) ae ai (3.0 pts) t prior to 3rd trifoliate t tropical spiderwort?

Tropical Spiderwort Management in RR Soybeans t Use Dual Magnum or generic PRE in known fields t tank-mix Pursuit or Classic with glyphosate t Extreme 3 pts/A = glyphosate (0.75 lb ai/A) + Pursuit (0.063 lb ai/A)

To Prevent Yield Loss in RR Soybeans  control weeds by 4-5 weeks after planting or  control weeds before they reach 6-9” in height or  control weeds before the V3 stage Source: Purdue University Extension Weed Science Group, 2004 (4.7 million acres of RR soybeans planted)

Sunflowers t Spartan t PPI or PRE t ozs/A t only soil applied broadleaf herbicide registered

University of Georgia Extension Weed Science (gaweed.com)