Impact of Cultural Practices on Soybean Aphid Incidence, Soybean Yield, and Virus Incidence

Transcription

1 Impact of Cultural Practices on Soybean Aphid Incidence, Soybean Yield, and Virus Incidence John Gaska, Dr. Craig Grau, Nancy Kurtzweil, and Dr. Dave Hogg Depts. of Agronomy, Plant Pathology and Entomology UW Madison

2 Possible Cultural Practices for Aphid-Virus Control Date of Planting Seeding rate Row width comparisons Varietal selection Tillage practices Fertility and fertilization Rotations? Canopy Density Virus free seed 2

3 Cultural Practices for Soybean Aphid Control Observations in 2000 High soybean aphid pressure in late planted fields High soybean aphid pressure in low plant population areas First instinct is to use insecticides Cultural practices may help also 3

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5 5 A p hid Count 8/11 Effect of planting date and variety on aphid incidence. Arlington, WI LSD 0.10 PD=24 Var=25 PDxV=ns Grau, Kurtzweil, 2000 AG2401 Span 201 Span May 22-May 1-Jun Date of Planting

6 Horsfall-Barratt Effect of planting date and variety on virus symptoms. Arlington, WI LSD 0.10 PD=0.7 Var=0.5 PDxV=ns 4-May 22-May 1-Jun Grau, Kurtzweil, 2000 AG2401 Span 201 Span 250 Date of Planting

7 Materials and Methods 2001 Date of Planting Study Location: Arlington Ag Research Station Expt. Design: RCB Reps: 4 Variety: DSR-215RR Row width: 30, 120,000 seeds/acre Planting dates: May 9, May 29, June 7 No insecticides were used 7

8 Yield (bu/a) Soybean Aphid Date of Planting Arlington, WI May 29-May 7-Jun 8 Planting Date

9 Aphids/Youngest Trifloliate Soybean Aphid Population vs. Planting Date Arlington, WI R3 stage 9-May R3 stage 27-May 7-June 9 13-Jul 20-Jul 27-Jul 3-Aug 10-Aug Sampling Date 17-Aug 24-Aug

10 Yield Difference (bu/a) Soybean Aphid On-Farm Observations Planting Date Variations Various WI Locations <May15 May 16-May31 June 1-June 28 Planting Date 2001-Wedberg, Jensen UW Dept. of Entomology 10

11 Which one does an aphid prefer?

12 Materials and Methods 2001 Row Spacing x Seeding Rate Study Location: Arlington Ag Research Station Expt. Design: RCB-Split Plot Reps: 4 Variety: DSR-215RR Row width: 7.5 and 30 Population: K, 200K, and 250 K seeds/acre 30 75K, 125K and 175K seeds/acre Planting date: May 9 No insecticides were used 12

13 13 Yield ( bu/a) Soybean grain yield at two row widths and three seeding rates. Arlington, WI LSD 0.10 RS=6.3 SR=3.4 RSxSR=7.4 Low Medium High 7.5" Row Spacing 30"

14 Aphids / youngest trifoliate Soybean aphids at two row widths and three seeding rates on July 19 and July 26. Arlington, WI July 19 Low Medium High July 26 Low Medium High 0 7.5" 30" Row Spacing 0 7.5" 30" Row Spacing 14

15 Planting date significantly affected aphid numbers No conclusions on viral activity due to planting date or plant density Insecticides may have to be used if aphid populations reach damaging levels Future research will build on aphid colonization numbers and correlate GDU s with aphid numbers Summary 15

16 Conclusions and Recommendations for Cultural Management of Soybean Insect-Virus Complex Early Planting Date Advantage Maintain dense canopy High yield potential Lower aphid density Lower virus incidence Disadvantage Bean leaf beetle BPMV Late Planting Date Use higher seeding rate for denser canopy May require an insecticide application Very late plantings may be able to mix herbicide and insecticide Use of virus free seed 16

17 Thank You! Questions? Comments? 17

18 The Soybean Virus-Insect Team Entomology John Wedberg Dave Hogg Tom German Tom Klubertanz Robb Alleman Bob Ellingson Scott Myers Plant Pathology Nancy Kurtzweil Mary Lee Ana Mondjana Lee Nolden Agronomy Chris Boerboom John Gaska Palle Pederson 18