Soybeans: Asian Soybean Rust (Phakopsora pachyrhizi)

Excerpt from Chapter 2, Field Crop Protection Guide, Order this publication

Table of Contents

1. Integrated Pest Management Options
   • Foliar Treatment
     • pyraclostrobin – Headline EC
     • azoxystrobin – Quadris
     • propiconazole – Tilt 250 E
     • azoxystrobin + propiconazole – Quilt
2. Related links...

Integrated Pest Management Options

Asian soybean rust is a new invasive fungal disease of soybean in North America. Scouting and early detection are critical to managing this disease. The early stages of the disease can be confused with other common foliar diseases such as septoria brown spot, bacterial pustule, downy mildew, frog-eye leaf spot and bacterial blight.

Numerous factors such as crop stage (R1 to R6), yield potential, disease risk or presence are critical components of the fungicide decision process. Strobilurin fungicides such as Headline or Quadris are protective products that stop spore germination and penetration into the soybean leaf. The strobilurins have no effect on the fungus once inside the leaf. Since the stobilurin group of fungicides have no curative activity, do not make solo applications of a strobilurin if any rust is present. The triazole fungicides such as Tilt and Folicur have varying protective abilities and are usually considered "early post-infection" fungicides. The post-infection or curative abilities are limited, and the fungicides may not perform well if 5%-10% disease is present in the lower crop canopy. Combination products containing both a strobulurin and triazole fungicide such as Quilt have preventative (pre-infection) and curative (post-infection) properties.

Yield loss is very likely once rust can be found in the mid-crop canopy. For these reasons, scouting, fungicide selection, timing and application are critical to successful management of soybean rust.

For further information on scouting techniques, sentinel plots, thresholds, management options and emergency use registrations, see OMAFRA Publication 811, Agronomy Guide for Field Crops, as well as the Ontario Soybean Growers website at www.soybean.on.ca

Foliar Treatment

Comments
Ground and aerial application. Maximum of 2 applications per year. Classified as a strobilurin fungicide; use in a preventative fungicide program (pre-infection). See label for resistance management strategy. 21 days to harvest interval.

Comments
Ground and aerial application. Maximum of 2 applications per year. Classified as a strobilurin fungicide; use in a preventative fungicide program (pre-infection). See label for resistance management strategy. 15 days to harvest interval.

Comments
Ground and aerial application. Make first application at the first sign of disease followed by a second application 14 days after the first application if environmental conditions are favourable for disease development. Maximum 2 applications per year. See label for resistance management strategy. 30 days to harvest interval.

Comments
Ground and aerial application. Make the first application at the first sign of disease. Apply the high rate only under conditions of high disease pressures. A second application at a 14-day interval may be needed if conditions persist. Good spray coverage and canopy penetration are important for best results. Apply in a minimum of 45 L of water per hectare. Maximum 2 applications per year. See label for resistance management strategy. 30 days to harvest interval.

Related links...

• Soybean Rust Infosheet
• Diseases
• Soybeans
• Ontario Soybean Growers

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