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Onion Disease Risk Assessment Bacterial Disease Forecasts (Xanthomonas, Pantoea, Slippery / Sour Skin & other bacteria) (update on a weekly basis) YOUR SCORE Total Rainfall (inches), summarize cumulative rainfall weekly up to Late Vegetative Growth Stage   Less than 0.1" [ 1 ] 0.1 - 0.5" [ 2 ] 0.5 - 1.0" [ 3 ] More than 1" [ 4 ]   Daily High Temperature (F), summarize weekly up to Late Vegetative Growth Stage   Less than 76 F [ 1 ] 76 - 81 F [ 2 ] 81 - 86 F [ 3 ] More than 86 F [ 4 ]   Forecasted Total Rainfall (inches), weekly between Late Vegetative and Late Bulbing Growth Stages   Less than 0.1" [ 1 ] 0.1 - 0.5" [ 2 ] 0.5 - 1.0" [ 3 ] More than 1" [ 4 ]   Forecasted Daily High Temperature (F), weekly between Late Vegetative and Late Bulbing Growth Stages   Less than 76 F [ 1 ] 76 - 81 F [ 2 ] 81 - 86 F [ 3 ] More than 86 F [ 4 ]   Forecasted Average Wind Speed (mph), weekly between Late Vegetative and Late Bulbing Growth Stages   Less than 1 mph [ 1 ] 1 - 5 mph [ 2 ] 5 - 10 mph [ 3 ] More than 10 mph [ 4 ]   Onion Rotation of less than 3 years, and/or initial bacterial infection (disease) confirmed in field or nearby   No onions (3 yr), No Disease [ 1 ] Recent onions OR Disease Nearby [ 2 ] Recent onions & Disease Nearby [ 4 ]   Yield Potential Estimate - in relation to plant population, fertility, irrigation, weeds, growing season   Low [ 1 ] Moderate [ 2 ] High [ 4 ]   Irrigation Practice or System   Drip-line System [ 1 ] Furrow or Gated Pipe [ 2 ] Sprinkler or Center Pivot [ 4 ]   Varietal Reaction to the Prevalent Bacterial Disease Threat   Resistant [ 1 ] Unknown [ 2 ] Susceptible [ 4 ]   Onion Disease Risk - TOTAL SCORE:

DISEASE RISK SUMMARY - If your Total Score was: more than 25 = High Risk 20 - 25 = Moderate Risk less than 20 = Reduced Risk

If the susceptible variety is planted in a field or region with a history of bacterial disease(s) and the total score was 20 or higher (moderate to high risk), treatment with a labeled bactericide (pre-package mix or tank mix with an EBDC fungicide, adjuvant, adequate gallonage, good coverage) as a protectant should be considered during the late vegetative (2 to 3 weeks pre-bulbing)) to the late bulbing (cropping or dry down) growth stages. Follow a 5 to 10 day interval between sprays, depending upon disease pressure and forecasted weather conditions. Pesticide Information available at: http://www.highplainsipm.org/

[ Strategy adapted for Colorado and surrounding region by Drs. H. F. Schwartz & D. H. Gent, M. S. McMillan, and K. L. Otto - 2008 ]

Onion Bacterial Disease - IPM STATEGY: Rotate to exclude susceptible hosts (i.e., onion volunteers, weeds) for 3 + years; examples of non-host crops include small grains and corn Avoid planting in fields with a history of disease during the last 3 years or near cull piles Plant resistant or less susceptible varieties if available