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

Bill Johnson and Earl CreechAssociate Professor and Graduate Research Assistant

Field in Knox Co., IN, Fall 2003

Winter Annual Weed Hosts of SCNCommon Chickweed

Henbit

Shepherd’s-purse

Purple Deadnettle

Venkatesh, R., Harrison, S. K., and Riedel, R. M. 2000. Weed hosts of soybean cyst nematode (Heterodera glycines) in Ohio. Weed Technol. 14:156-160.

Winter Weed Species in Indiana Fields

---Number of fields---

10013-146310-122107-97104-6161-3

South (26)North (29)# of species/field

SCN Hosts in Indiana Fields

---Number of fields---

915-61473-43171-2040

South (26)North (29)# of SCN hosts/field*

*Confirmed hosts - henbit, deadnettle, shepherd’s-purse, field pennycress, common chickweed, smallflowered bittercress

Reproduction of SCN on Purple Deadnettle

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

Reproduction of SCN on Purple Deadnettle

Recovered cysts from PDN and reinoculatedWilliams soybean varietyRecovered new cysts from soybean after 6 weeks1st confirmed report of SCN reproduction on PDN in the field.

Creech, J. E., Johnson, W. G., Faghihi, J., Ferris, V. R., and Westphal, A. 2005. First report of soybean cyst nematode reproduction on purple deadnettle under field conditions. Online. Crop Management doi:10.1094/CM-2005-0715-01-BR.Venkatesh, R., Harrison, S. K., Regnier, E. E., and Riedel, R. M. 2004. Purple deadnettle effects on soybean cyst nematode populations in no-till soybean. Proc. North Central Weed Sci. Soc. 59:56.4.

Soybean Cyst Nematode (SCN)

Microscopic round wormCysts contain up to 600 eggsFound 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. 2003. Effect of diseases on soybean yields in the United States and Ontario (1999-2002). Online. Plant Health Progress doi:10.1094/PHP-2003-0325-01-RV.

SCN Management Recommendations

1. Crop rotation2. SCN resistant

varieties

Role of winter annual weed

management??

Objectives

To determine the effect of various winter weed management tactics and crop rotation on:

1. SCN populations 2. Winter weed seedbank

Materials and MethodsSeptember 2003Agronomy Center for Research and Education (ACRE)

Chalmers silty clay loamLow weed, low SCN

Southwest Purdue Agricultural Center (SWPAC)

Patton silt loamHigh weed, high SCN

SWPAC

ACRE

Treatments

Split-plot design with 6 replicationsCrop Rotations

1. Soybean-Soybean2. Soybean-Corn

Winter Weed Management Tactics1. No herbicide application2. Fall + spring herbicide applications3. Spring herbicide application4. Fall herbicide application 5. Annual ryegrass cover crop6. Winter wheat cover crop

Materials and Methods

Plots measured 9.1 x 12.2 mWinter wheat border around plots to prevent soil movementGlyphosate or glufosinate for fall, spring, and in-crop applications Burndown application prior to plantingCrops planted in 76 cm rowsLong term experiment (at least 4 growing seasons)

Data CollectionHarvested center 4 (SWPAC) or 8 (ACRE) rows of plots and adjusted soybean yields to 13% moisture38 soil cores/plot at harvest and at planting

1. SCN counts by Purdue Nematology Lab2. Weed seedling emergence

technique1,500 cc soil26 x 26 cm flats

Data Analysis

RCBD with 12 replicationsSCN 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.

Number of Seedlings Emerged from Seedbank – SWPAC (2004)

No WeedControl

Weed Free SpringApplied

Herbicide

FallApplied

Herbicide

FallSeededWheat

FallSeeded

Ryegrass

# se

edlin

gs /

1500

cc

soil a

cc

bc

b b

62

2731

38

45 45

Number of Seedlings Emerged from Seedbank – ACRE (2004)

No WeedControl

Weed Free SpringApplied

Herbicide

FallApplied

Herbicide

FallSeededWheat

FallSeeded

Ryegrass

# se

edlin

gs /

1500

cc

soil a

cdd

bcd bcb

18

2.21.2

2.5 2.94.1

SCN Egg Density - SWPAC

0

1000

2000

3000

4000

5000

6000

Spring 2004 Fall 2004 Spring 2005

SCN

egg

s / 1

00 c

c so

il

No Weed ControlWeed FreeSpring Applied Herb.Fall Applied Herb.Fall Seeded WheatFall Seeded Ryegrass

Treatment

P = 0.7156

SCN Egg Density - ACRE

0

50100

150

200250

300

350400

450

Spring 2004 Fall 2004 Spring 2005

SCN

egg

s / 1

00 c

c so

il

No Weed ControlWeed FreeSpring Applied Herb.Fall Applied Herb.Fall Seeded WheatFall Seeded Ryegrass

Treatment

P = 0.1904

Purple Deadnettle and Henbit Density

ACRE – less than 1 plant /sq. m.SWPAC – 12 plants / sq. meter

2004 Soybean Yield - SWPACSo

ybea

n yi

eld

(kg/

ha)

No WeedControl

Weed Free SpringApplied

Herbicide

FallApplied

Herbicide

FallSeededWheat

FallSeeded

Ryegrass

aa a a

aa

35403140 3200 3110

3430 3510

2004 Soybean Yield - ACRESo

ybea

n yi

eld

(kg/

ha)

No WeedControl

Weed Free SpringApplied

Herbicide

FallApplied

Herbicide

FallSeededWheat

FallSeeded

Ryegrass

ab aba ab

bc

3910 39404160 4050

34803780

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!

Future Studies

Fall weed control timing may be the most important factorFocus on fields that contain the best overall host – purple deadnettle

Thanks!Indiana Soybean BoardUSDA NCIPM Competitive Grants Program