Impact of Winter Weed Management and Crop Rotation on Winter Annual Weeds and Soybean Cyst Nematode

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1 Impact of Winter Weed Management and Crop Rotation on Winter Annual Weeds and Soybean Cyst Nematode Bill Johnson and Earl Creech Associate Professor and Graduate Research Assistant

2 Field in Knox Co., IN, Fall 2003

3 Winter Annual Weed Hosts of SCN Common Chickweed Henbit Shepherd s-purse Purple Deadnettle Venkatesh, R., Harrison, S. K., and Riedel, R. M Weed hosts of soybean cyst nematode (Heterodera glycines) in Ohio. Weed Technol. 14:

4 Winter Weed Species in Indiana Fields # of species/field North (29) South (26) ---Number of fields

5 SCN Hosts in Indiana Fields # of SCN hosts/field* North (29) South (26) ---Number of fields *Confirmed hosts - henbit, deadnettle, shepherd s-purse, field pennycress, common chickweed, smallflowered bittercress

6 Reproduction of SCN on Purple Deadnettle PDN plants collected from NT soybean field at SWPAC in mid October 2004 Examined roots of 10 PDN plants and found SCN cysts on 9/10

7 Reproduction of SCN on Purple Deadnettle Recovered cysts from PDN and reinoculated Williams soybean variety Recovered new cysts from soybean after 6 weeks 1 st confirmed report of SCN reproduction on PDN in the field. Creech, J. E., Johnson, W. G., Faghihi, J., Ferris, V. R., and Westphal, A First report of soybean cyst nematode reproduction on purple deadnettle under field conditions. Online. Crop Management doi: /cm br. Venkatesh, R., Harrison, S. K., Regnier, E. E., and Riedel, R. M Purple deadnettle effects on soybean cyst nematode populations in notill soybean. Proc. North Central Weed Sci. Soc. 59:56.4.

8 Soybean Cyst Nematode (SCN) Microscopic round worm Cysts contain up to 600 eggs Found in most soybean growing regions of U.S. In 2002, estimated yield losses in U.S. were $783.8 million (Wrather et al. 2003) Wrather, J. A., S.R. Koenning, and T.R. Anderson Effect of diseases on soybean yields in the United States and Ontario ( ). Online. Plant Health Progress doi: /php rv.

9 SCN Management Recommendations 1. Crop rotation 2. SCN resistant varieties Role of winter annual weed management??

10 Objectives To determine the effect of various winter weed management tactics and crop rotation on: 1. SCN populations 2. Winter weed seedbank

11 Materials and Methods September 2003 Agronomy Center for Research and Education (ACRE) Chalmers silty clay loam Low weed, low SCN Southwest Purdue Agricultural Center (SWPAC) Patton silt loam High weed, high SCN SWPAC ACRE

12 Treatments Split-plot design with 6 replications Crop Rotations 1. Soybean-Soybean 2. Soybean-Corn Winter Weed Management Tactics 1. No herbicide application 2. Fall + spring herbicide applications 3. Spring herbicide application 4. Fall herbicide application 5. Annual ryegrass cover crop 6. Winter wheat cover crop

13 Materials and Methods Plots measured 9.1 x 12.2 m Winter wheat border around plots to prevent soil movement Glyphosate or glufosinate for fall, spring, and in-crop applications Burndown application prior to planting Crops planted in 76 cm rows Long term experiment (at least 4 growing seasons)

14 Data Collection Harvested center 4 (SWPAC) or 8 (ACRE) rows of plots and adjusted soybean yields to 13% moisture 38 soil cores/plot at harvest and at planting 1. SCN counts by Purdue Nematology Lab 2. Weed seedling emergence technique 1,500 cc soil 26 x 26 cm flats

15 Data Analysis RCBD with 12 replications SCN and seedbank data were analyzed with covariate analysis. Mean separations with t- tests. Yield data subjected to ANOVA and means separated with Fisher s Protected LSD.

16 Number of Seedlings Emerged from Seedbank SWPAC (2004) 62 # seedlings / 1500 cc soil a 27 c 31 c 38 bc b b No Weed Control Weed Free Spring Applied Herbicide Fall Applied Herbicide Fall Seeded Wheat Fall Seeded Ryegrass

17 Number of Seedlings Emerged from Seedbank ACRE (2004) 18 # seedlings / 1500 cc soil a 2.2 cd 1.2 d bcd bc 4.1 b No Weed Control Weed Free Spring Applied Herbicide Fall Applied Herbicide Fall Seeded Wheat Fall Seeded Ryegrass

18 SCN Egg Density - SWPAC SCN eggs / 100 cc soil Treatment P = No Weed Control Weed Free Spring Applied Herb. Fall Applied Herb. Fall Seeded Wheat Fall Seeded Ryegrass 0 Spring 2004 Fall 2004 Spring 2005

19 SCN Egg Density - ACRE SCN eggs / 100 cc soil Treatment No Weed Control P = Weed Free Spring Applied Herb. Fall Applied Herb. Fall Seeded Wheat Fall Seeded Ryegrass Spring 2004 Fall 2004 Spring 2005

20 Purple Deadnettle and Henbit Density ACRE less than 1 plant /sq. m. SWPAC 12 plants / sq. meter

21 2004 Soybean Yield - SWPAC Soybean yield (kg/ha) 3540 a a a a a a No Weed Control Weed Free Spring Applied Herbicide Fall Applied Herbicide Fall Seeded Wheat Fall Seeded Ryegrass

22 2004 Soybean Yield - ACRE Soybean yield (kg/ha) ab ab a ab 3480 c 3780 b No Weed Control Weed Free Spring Applied Herbicide Fall Applied Herbicide Fall Seeded Wheat Fall Seeded Ryegrass

23 Conclusions 1. To reduce seedbank, spring herbicide application timing most effective 2. Winter wheat negatively influenced soybean yield on heavier soils 3. At low weed populations, winter annual weed management does not appear to impact SCN egg density 4. However, the story is not complete!

24 Future Studies Fall weed control timing may be the most important factor Focus on fields that contain the best overall host purple deadnettle Thanks! Indiana Soybean Board USDA NCIPM Competitive Grants Program