Effects of Isoxadifen on Field Corn Injury and Yield …

1 Effects of Isoxadifen on Field corn Injury Effects of Isoxadifen on Field corn Injury and Yield from sulfonylurea Herbicidesand Yield from sulfonylurea Prostko Prostko Professor and Extension Weed SpecialistProfessor and Extension Weed SpecialistDepartment of Crop & Soil SciencesDepartment of Crop & Soil SciencesINTRODUCTIONINTRODUCTIONI soxadifen is a corn safener that was originally developed by BIsoxadifen is a corn safener that was originally developed by Bayer ayer CropScience. When applied in combination with certain postemergCropScience. When applied in combination with certain postemergence ence herbicides , Isoxadifen increases crop selectivity by enhancing herbicides , Isoxadifen increases crop selectivity by enhancing metabolic metabolic degradation.

2 Isoxadifen is a component of several corn herbiciddegradation. Isoxadifen is a component of several corn herbicides such as es such as Laudis, Option, and Status. DuPont recently released a Laudis, Option, and Status. DuPont recently released a QQ line of herbicides line of herbicides that also contain Isoxadifen (Resolve Q and Steadfast Q). Histothat also contain Isoxadifen (Resolve Q and Steadfast Q). Historically, the use of rically, the use of sulfonylurea herbicides in corn has been prohibited in fields tsulfonylurea herbicides in corn has been prohibited in fields that were treated hat were treated with an OP soil insecticide such as Counter.

3 Therefore, the objwith an OP soil insecticide such as Counter. Therefore, the objective of this ective of this research was to determine if the new research was to determine if the new QQ formulations of sulfonylurea herbicides formulations of sulfonylurea herbicides could be used in Field corn treated with Counter. could be used in Field corn treated with Counter. MATERIALS AND METHODSMATERIALS AND METHODSA small plot Field trial was conducted in 2010 at the UGA PonderResearch Farm. The experimental design was a randomized complete block with a factorial arrangement of treatments replicated four times.

4 Treatments were all possible combinations of two in-furrow soil insecticide applications (-Counter 15G or Counter 15G @ 7 oz/1000 row feet) and four postemergence (POST) herbicides (Resolve Q, Resolve, Steadfast Q, and Steadfast) applied at 1X and 2X rates. The corn hybrid DKC 67-21RR was planted on March 25. POST herbicides were applied on April 13 (19 DAP) using a CO2-pressurized backpack sprayer with 11002DG nozzles calibrated to deliver 15 GPA. The entire plot area was maintained weed-free using a combination of mechanical cultivation, hand-weeding, and a timely POST application of Roundup WeatherMax + Atrazine + Prowl H2O.

5 All data were subjected to ANOVA and means separated using Fischer s Protected LSD Test at P = AND DISCUSSIONRESULTS AND DISCUSSION1)1) corn Injury was greater when any herbicide was applied followingCorn Injury was greater when any herbicide was applied followingan inan in--furrow furrow soil application of Counter (Figures 1, 2, and 3).soil application of Counter (Figures 1, 2, and 3).2)2)When applied at 1X rates following Counter, the When applied at 1X rates following Counter, the QQ formulations caused 21formulations caused 21--27% less crop Injury when compared to the non27% less crop Injury when compared to the non--safened formulations.

6 Safened formulations .3)3)When applied at 2X rates following Counter, the When applied at 2X rates following Counter, the QQ formulations caused 30formulations caused 30--37% less crop Injury when compared to the non37% less crop Injury when compared to the non--safened formulations .safened formulations .4)4)Despite causing obvious visible Injury symptoms when applied folDespite causing obvious visible Injury symptoms when applied following lowing Counter, the Counter, the QQ formulations did formulations did notnotcause significant corn Yield losses (Figures cause significant corn Yield losses (Figures 4 and 5).

7 However, non4 and 5). However, non--safened formulations caused a 43safened formulations caused a 43--65% Yield loss when 65% Yield loss when applied following following 1. Crop Safener ( Isoxadifen ) Effects on corn Stunting (22 DAT) -1X Herbicide Rates13681031582950010203040506070 Resolve QResolveSteadfast QSteadfastNo CounterCounterCN-12-10 LSD = 11 HerbicideStunting(%)Figure 2. Crop Safener ( Isoxadifen ) Effects on corn Stunting (22 DAT) -2X Herbicide Rates1613141436662663010203040506070 Resolve QResolveSteadfast QSteadfastNo CounterCounterCN-12-10 LSD = 11 HerbicideStunting (%)Figure 3. Steadfast/Counter Interactions1X RatesCN-12-10 May 522 DATNo CounterSteadfast QCounterSteadfast Q(+ Isoxadifen )CounterSteadfast(- Isoxadifen ) Figure 4.

8 Crop Safener ( Isoxadifen ) Effects on corn Yield -1X Herbicide Rates11612912212611369128720204060801001 20140 Resolve QResolveSteadfast QSteadfastNo CounterCounterCN-12-10 LSD = 22CV = 5. Crop Safener ( Isoxadifen ) Effects on corn Yield -2X Herbicide Rates11813012013210546118610204060801001 20140 Resolve QResolveSteadfast QSteadfastNo CounterCounterCN-12-10 LSD = 22CV =