Crop Rotation and Herbicide Use Influence. Horseweed (Conyza canadensis) in No Till Crop. Purdue University

Transcription

1 Crop Rotation and Herbicide Use Influence Population Dynamics of Glyphosate Resistant Horseweed (Conyza canadensis) in No Till Crop Management Systems Vi M D i K i D Gib d Willi G J h Vince M. Davis, Kevin D. Gibson, and William G. Johnson, Purdue University

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3 Horseweed Seed Production Capsule 4-8mm Avg 32 (+7) seeds/capsule when grown in competition with soybean Seed and Pappus 3-5mm 1-2mm

4 Horseweed Prone to evolve herbicide resistance One of the top ten most important herbicide resistant weeds worldwide 40 documented d cases on Herbicide id Resistance Website 13 different countries, many different herbicides Including glyphosate-resistant biotypes in 16 states and 5 countries

5 Glyphosate-Resistant (GR) Horseweed Indianapolis In Indiana Found in 29 / 92 counties GR biotypes are most frequently found in the southeastern region 4 times more continuous soybean than rest of state Southeastern Purdue Agriculture Center (SEPAC) centrally located Glyphosate-Resistant t t Glyphosate-Susceptible

6 Management Options Long-term no-till field experiment Established at SEPAC Fall 2003 Fall 2007 Study area was previously in a no-tillage management system contained a moderate infestation glyphosatecontained a moderate infestation glyphosate resistant horseweed escapes (1 plant m -2 )

7 Hypothesis Integrated Weed Management systems would shift the population dynamics of mixed glyphosate-resistant t t and susceptible horseweed populations

8 Materials and Methods *Replication 1 and border corn Rotation Design S S S S S C S C Special design considerations Plot size 4.5 by 4.5 meters 6 rows of border corn planted bi-directional to surround each plot to limit seed movement

9 Treatment and Data Collection Timeline Trt Fall Spring In-Crop # treatments treatments treatments 1. Oc ctober glyphosate 2. - glyphosate March soil sam mples 3. residual residual 5. residual - soil sam mples 6. - residual 7. cover crop terminate CC 8. cover crop terminate CC - Oc Cro A August s ctober p harve soil sam est / Se soil sam mples eed Rain mples

10 Treatment and Data Collection Timeline Trt Fall Spring In-Crop # treatments treatments treatments 1. Oc ctober glyphosate March soil sam mples - glyphosate 2. - glyphosate glyphosate 3. residual - glyphosate 4. - residual glyphosate 5. residual - nonglyphosate 6. - residual non- glyphosate soil sam mples Oc Cro A August s ctober p harve soil sam est / Se soil sam 7. cover crop terminate CC glyphosate 8. cover crop terminate CC non- glyphosate mples eed Rain mples

11 Crop Rotation 2005 October 2005 Source Adults Seedbank P>F F P>F F Rotation Rotation* ti Treatment All seedling and plant counts are pooled over crop rotations Treatment N=10

12 Seedbank Density dry soi il Se eedling gs kg Treatments Oct-03 Apr-04 Oct-04 Apr-05 Oct-05 Sample Timing

13 Seedbank Density Se eedling gs kg -1 dry soil Fall glyphosate fb glyphosate Treatments Oct-03 Apr-04 Oct-04 Apr-05 Oct-05 Sample Timing

14 Initial SEPAC S:R Seedbank Ratio 452 transplanted horseweed seedlings sprayed with 1.7 kg ae ha -1 survivors at 21DAT were followed by 3.4 kg ae ha -1 76% resistant t or 1:3 S:R *21 DA 4X glyphosate

15 SEPAC Glyphosate-Resistant Seedbank % (n=452) % (n=50) % (n=46) Most plants came from exclusive glyphosate system! *21 d after 4X glyphosate

16 Conclusions cuso s No influence from crop rotation Viable horseweed seed persistence declines rapidly during the spring and summer months Seedbank reliant on annual seed rain event To maximize crop yield apply residual herbicide in the spring prior to crop planting Davis et al Weed Sci. 55: Experiment continued.

17 Crop Rotation Year Crop rotation Adult plants Seedbank plants P>F F 10 m -2 Plants kg dry soil -1 P>F F

18 Crop Rotation Year Crop rotation Adult plants Seedbank plants P>F F 10 m -2 Plants kg dry soil -1 soybean-soybean soybean-corn P>F F

19 Crop Rotation Year Crop rotation Adult plants Seedbank 2006 plants P>F F 10 m -2 Plants kg dry soil -1 soybean-soybean soybean-corn P>F F soybean-soybean 29 soybean-corn 14 <

20 SEPAC Glyphosate-Resistant Seedbank % (n=452) % (n=50) Densities but % GR % (n=46) % (n=85) Rotation S:R shifts = NS System S:R shifts = NS % (n=1022) Rotation S:R shifts = NS System S:R shifts = *** *21 d after 4X glyphosate

21 SEPAC S:R Seedbank Ratio 2007 Proper herbicide application timing is important! Residual control and herbicide rotation is important! Preplanned contrasts Fall preplant timing vs. Spring preplant timing Glyphosate Glyphosate- Chi- -resistant susceptible square plants plants <0.0001

22 SEPAC S:R Seedbank Ratio 2007 Proper herbicide application timing is important! Residual control and herbicide rotation is important! Preplanned contrasts Glyphosate Glyphosate- Chi- -resistant susceptible square plants plants Fall preplant timing vs Spring preplant timing < Glyphosate fb glyphosate vs No glyphosate at preplant or post <0.0001

23 SEPAC S:R Seedbank Ratio 2007 Proper herbicide application timing is important! Residual control and herbicide rotation is important! Preplanned contrasts Glyphosate Glyphosate- Chi- -resistant susceptible square plants plants Fall preplant timing vs Spring preplant timing < Glyphosate fb glyphosate vs No glyphosate at preplant or post < Residual fb glyphosate post vs Residual fb NON-glyphosate post 4 24 <

24 Conclusions Horseweed densities were greater in continuous soybean systems. This supported Indiana in-field survey results. SR S:R ratio shifted dfrom 13t 1:3 to 61 6:1 after four years in systems using residual herbicides and no postemergence glyphosate

25 Any Questions? Purdue Weed Science Website