1. Reemerging Weed Problem in Wisconsin -or-What was Old is New Again Tim Trower, Mark Renz, Bryan Jensen and Larry Binning University of Wisconsin

2. The Culprits

3. Why the Resurgence? Both weeds are perennials Shift to reduced and no-till tillage systems favors both weeds Changes in herbicide programs may favor survival Glyphosate not always the most efficacious program Application timing may not be optimum

4. Dandelion- Taraxacum officinale“Built to Last” Deep-rooted perennial Tap root can reach six feet in length Early riser in the spring Are some of the first weeds to green-up in the spring Early seed production Begins in late April or early spring at the Arlington Research station Seeds are viable and can germinate the same year

5. Dandelions“Application timing, what is best?” Weed biology can make optimum application timing difficult Fall applications traditionally are the most efficacious Translocating herbicides such as glyphosate and the synthetic auxins move into the tap root But application timing is limited by harvest and weather

6. Dandelions“Application timing, what is best?” Spring applications have been less effective Application timing can be delayed by weather and planting interval Trials conducted at the Arlington Research Station in 2009 and 2010 to determine dandelion control with fall and spring applications Application information: RCB, four replicates, 10’ X 25’ plots 20 GPA, XR8003 tips, 23 PSI, 3 MPH

7. Dandelion ControlFall compared to Spring Applications

8. Percent Dandelion ControlFall Compared to Spring

9. Dandelion ControlFall applied and evaluated the following spring Canopy EX @ 1.1 oz/a + 2,4-D @ 16 fl oz + PowerMax @ 21 fl oz 2,4-D @ 32 fl oz + PowerMax @ 21 fl oz Synchrony @ 0.375 oz/a + 2,4-D @ 16 fl oz + PowerMax @ 21 fl oz Enlite @ 2.8 oz/a + PowerMax @ 21 fl oz

10. Conclusions Fall-applied Canopy EX, Synchrony and Enlite tank mixes all provided better dandelion control at spring green-up that 2,4-D/glyphosate. All fall-applied treatments gave better early-season dandelion control which coincides with normal corn planting. Conversely, spring-applied 2,4-D/glyphosate, Synchrony and Enlite tank mixes provided better late-season dandelion control which coincides with normal soybean planting.

11. Conclusions Fall-applied Canopy EX followed by an in-season glyphosate application provided 93% dandelion control at harvest. Dandelion growth stage is important Seedlings much easier to control than mature plants Spring applications of contact herbicides generally do a good job on the seedlings No yield differences were observed.

12. Percent Dandelion Control:Fall-applied treatments

13. Conclusions Autumn, Canopy EX, Synchrony, Express and Sharpen tank mixes all provided 90% or greater dandelion control at spring green-up. Dandelion control decreased with most treatments at the mid and late evaluations. The Canopy EX tank mix was the best overall treatment, followed by Autumn and Express tank mix. No yield differences were observed.

14. Field Horsetail- Equisetum arvensePlant Biology Perennial Spreads by rhizomes and spores Tan-colored stalks are the first to emerge in the early spring- Followed by the vegetative stage-

15. Field Horsetail Competitive plant that can cause yield reductions. Generally starts at the edge of the field and slowly spreads. Favors low spots Three trials were conducted in 2009 and 2010 in grower fields. Application information: RCB, four replicates, 10’ X 25’ plots 20 GPA, XR8003 tips, 23 PSI, 3 MPH

16. Field HorsetailAddition Information With the exception of two treatments, Dual II Magnum plus atrazine was applied preemergence to reduce competition from non-target weeds. Postemergence herbicide treatments were targeted for corn at the V3 growth stage. Plots were hand-harvested in 2009 and machine harvested in 2010.

17. 2009 Monroe County Percent Ground Cover Means followed by same letter do not significantly differ (P=.05)

18. 2009 Columbia County Percent Ground Cover Means followed by same letter do not significantly differ (P=.05)

19. 2010 Sauk County Percent Ground Cover Means followed by same letter do not significantly differ (P=.05)

20. ConclusionsField Horsetail Results between years and locations were variable. Steadfast/Status applied postemergence provided the best field horsetail control in two studies. Steadfast/Hornet applied postemergence was effective in one study. Soil-applied programs provide varying degrees of suppression but were generally ineffective after mid-season. Python applied preemergence provided acceptable control in only one trial. Significant yield decrease in one study.

21. Summary Both weed species are favored by reduced tillage. Both species require a system approach to provide best results: Scout fields often, don’t let the weed increase in the “background” Crop rotation Sequential herbicide applications Application timings Fall compared to spring Tillage? May be required under severe weed pressure