Fungal and Bacterial leaf spots of soybean; How not to confuse these with soybean rust
36 Pages
English

Fungal and Bacterial leaf spots of soybean; How not to confuse these with soybean rust

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    Institute of Ag Professionals Proceedings of the 2004 Crop Pest Management Shortcourse www.extension.umn.edu/AgProfessionals Do not reproduce or redistribute without the written consent of author(s). Foliar diseases of soybean that look like soybean rust.Jim KurleDepartment of Plant PathologyUniversity of Minnesota - St. PaulSoybean Rust in Minnesota• Unlikely that Rust will Overwinter in MN• Rust will Survive in Gulf Coastal Areas – Texas, Louisiana, Florida• Spores will Follow the “PucciniaPathway”• Risk Analysis Indicates Likelihood of Weather Conditions Favorable for Epidemic – 6 to 15 out of 30 Years.Soybean Rust Management• Currently – No Resistant Varieties Available• Management – Timely Application of Fungicides• Protectant Fungicides – Applied Before Infection• Eradicant & Curative Fungicides – Provide Control after Infection (Must be applied very early in disease cycle.)• Identification of soybean rust will be critical.Soybean Rust Identification• Identification of soybean rust requires training and experience.• A number of other foliar diseases are easily confused with soybean rust.• This presentation is intended to help you identify those diseases that can be confused with soybean rust.• By eliminating instances where “lookalike” diseases occur diagnostic resources can be focused on symptoms that might be those of soybean rust.Soybean Rust• Disease Development is favored by: – ...

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Language English
     Institute of Ag Professionals  
   Proceedings of the  2004 Crop Pest Management Shortcourse    www.extension.umn.edu/AgProfessionals     Do not reproduce or redistribute without the written consent of author(s).
Foliar diseases of soybean that look like soybean rust.
Jim Kurle
Department of Plant Pathology
University of Minnesota - St. Paul
Soybean Rust in Minnesota
Unlikely that Rust will Overwinter in MN
Rust will Survive in Gulf Coastal Areas
–Texas, Louisiana, Florida
Spores will Follow the “Puccinia Pathway”
Risk Analysis Indicates Likelihood of Weather Conditions Favorable for Epidemic – 6 to 15 out of 30 Years.
Soybean Rust Management
Currently – No Resistant Varieties Available
Management – Timely Application of Fungicides
Protectant Fungicides – Applied Before Infection
Eradicant & Curative Fungicides – Provide Control after Infection (Must be applied very early in disease cycle.)
Identification of soybean rust will be critical.
Soybean Rust Identification
Identification of soybean rust requires training and experience. A number of other foliar diseases are easily confused with soybean rust. This presentation is intended to help you identify those diseases that can be confused with soybean rust. By eliminating instances where “lookalike” diseases occur diagnostic resources can be focused on symptoms that might be those of soybean rust.
Soybean Rust
Disease Development is favored by:
–Prolonged leaf wetness,
–High humidity (>75-80%).
–Temperatures between 59-86 F,
Optimum 77 F
–Presence of Spores
Soybean Rust
Obligate parasite.
Infection begins on lower, older, leaves.
Initially forms chlorotic “spots”.
Leaf may become chlorotic.
Spots become “lesions”.
Lesions develop into “pustules” and increase in size; change from gray to tan or reddish brown.
Soybean Rust
Pustules may also occur on stems, petioles, and pods.
Pustules break open and reveal tan to reddish brown spores.
Soybean Rust
When scouting for soybean rust, focus on:
Early planted fields with early maturing varieties.
Low lying or protected fields with prolonged dew periods.
Fields with early canopy closure.
Soybean Rust
For soybean rust detection on the plant:
Examine lower leaves of the plant.
Use a 10 to 20X hand lens to detect pustules on underside of leaves.
Use a 10 to 20X hand lens to detect spores released from pustules.
Soybean Rust Lesions
http://www.aphis.usda.gov/lpa/issues/sbr/Soybean Rust 22.pdf _ _