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 Spot Photo by G. Ruhl Bacterial Pustule Photo by G. Hartman Downy Mildew Spores Photo 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 1 st to 3 rd 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

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What happened in 2005? Spore Trapping County Spores trapped Disease detected Difference in days Colquitt5 July3 August+31 Laurens29 July3 August+5 Washington5 July30 August+55 Sumter5 July18 August+34 Decatur28 June21 July+23 Tift (trap 1)15 August15 July-31 Tift (trap 2)21 JulyNoneNA Appling28 JuneNoneNA ToombsNone NA BurkeNone 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 – 1 st 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