Asian Soybean Rust Monitoring in 2005 and 2006

Dr. Layla Sconyers

Dr. Robert Kemerait

Dr. Philip Jost

Dr. Dan Phillips

Research Associate

Extension Plant Pathology

Extension Crop and Soil Science

Plant Pathology

University of Georgia

College of Agricultural and Environmental Sciences

Symptoms• Brick-red spots on upper leaf

surface

• Pustules form on lower leaf surface

• Leaves yellow and defoliate

• Confused with other foliar diseases!

• YOUNG infections MAY BE MISSED– 1-2 pustules per leaf– Color range: clear, tan, red

Similar Diseases

Septoria Brown SpotPhoto by G. Ruhl

Bacterial PustulePhoto by G. Hartman

Downy Mildew SporesPhoto by J. Brock

Disease Development• Fungal spores = urediniospores

• Wind or wind-blown rain

• Land on leaf, penetration

• Pustules form after about 10 days

• 1 pustule can produces spores for 3 wks

• More wind = more infections

• Canopy closure and crop flowering

400X

60X

Disease Development

• Totally defoliates plant or until environment is no longer conducive

• 59-84°F optimal range, long dew periods

• Defoliation can occur 4-6 wks from initial infection

2005 Sentinels

• 25 total sentinel plots in GA– 3 clover– 5 kudzu– 17 soybean sentinels

• Sentinels scouted weekly

• Soybean: 50’ X 50’ plots– MG II, III, IV planted from 1st to

3rd wk of April

D. Hershman

2005 Disease Monitoring• 100 leaves or leaflets examined

– Visually– Dissection microscopy (60-80X)

• Soybean: 40 lower, 40 mid, 20 upper canopies = 100 leaflets

• Severity (low, moderate, or heavy)

• Incidence (leaflets infected of total collected)

• First finds for each county were confirmed by PCR or UGA trained expert

2005 Spore Trapping

• 10 spore traps provided by Syngenta

• Placed in center of each soybean sentinel

• Slides changed weekly

• Analyzed by J. Rupe, U. Ark.

D. Hershman

2005 Spore Trapping

*1,2,3*4,5

*6,7

*8

*9

*10,11*12

*13,14

*15

*16

*17

*18

*19,20,21

*23

*25

*22

*24

Spore traps were placed at #6, 7, 8, 10, 16, 17, 18, 22, 23, and 25 on map

What happened in 2005?Disease Monitoring

• Clover = no rust• Kudzu = 1 of 5 sites had

rust• Soybean = 13 of 17 sites

had rust

• First find: Seminole County• First sentinel: Tift County,

Lang Research Farm

• First commercial farm: Appling County

• 33 counties by Nov 3 – ~60 miles per wk

SBR Observation – 02-16-2005SBR Observation – 02-23-2005SBR Observation – 03-02-2005SBR Observation – 03-09-2005SBR Observation – 03-16-2005SBR Observation – 03-23-2005SBR Observation – 03-30-2005SBR Observation – 04-06-2005SBR Observation – 04-13-2005SBR Observation – 04-20-2005SBR Observation – 04-27-2005SBR Observation – 05-04-2005SBR Observation – 05-11-2005SBR Observation – 05-18-2005SBR Observation – 05-25-2005SBR Observation – 06-01-2005SBR Observation – 06-08-2005SBR Observation – 06-15-2005SBR Observation – 06-22-2005SBR Observation – 06-29-2005SBR Observation – 07-06-2005SBR Observation – 07-13-2005SBR Observation – 07-20-2005SBR Observation – 07-27-2005SBR Observation – 08-03-2005SBR Observation – 08-10-2005SBR Observation – 08-17-2005SBR Observation – 08-24-2005SBR Observation – 08-31-2005SBR Observation – 09-07-2005SBR Observation – 09-14-2005SBR Observation – 09-21-2005SBR Observation – 09-28-2005SBR Observation – 10-05-2005SBR Observation – 10-12-2005SBR Observation – 10-19-2005SBR Observation – 10-26-2005SBR Observation – 11-02-2005SBR Observation – 11-09-2005SBR Observation – 11-11-2005

What happened in 2005? Spore Trapping

CountySporestrapped

Diseasedetected

Difference in days

Colquitt 5 July 3 August +31

Laurens 29 July 3 August +5

Washington 5 July 30 August +55

Sumter 5 July 18 August +34

Decatur 28 June 21 July +23

Tift (trap 1) 15 August 15 July -31

Tift (trap 2) 21 July None NA

Appling 28 June None NA

Toombs None None NA

Burke None None NA

2006 Sentinels• Number based on funding from USDA and NCSRP

• At least 22 in Georgia

• Clover or lupine

• Kudzu– Overwintering sentinels– 10 in Georgia

• Soybean– Disease monitoring– Spore trapping

2006 Sentinels• Protocol modified

• Scouting interval: every two weeks until bloom

• Collect 100 leaflets from lower soybean canopy

• Dissection microscopy (40 – 60X)

• Incubation (24-48 hr)

• Need for education and training

Yorinori

Summary• Rust can be detrimental if undetected and infects early

in growing season (S. America)

• Rust CAN be managed

• Proactive scouting and monitoring needs to continue in 2006

• Communication with county agents and extension specialists – need to know what to scout for!

• Timely fungicide applications with good products – 1st application VERY important

• Still a learning process…we do not have all the answers yet

Acknowledgements• Georgia:

– Bob Kemerait, Dan Phillips, Phil Jost, Roger Boerma, Jason Brock, John Sherwood, Rick Jackson, Michael Foster

– Growers Mr. Billy Wayne Sellers, Mr. Glen Waller, Mr. Vic Thigpen

– Research farm managers and their crews

– County agents• John Rupe, U. Arkansas• USDA and NCRSP• Syngenta