How far and how fast can we expect this disease to spread?

Soybean rust dispersal is highly dependent on environmental conditions. Once the pathogen is present, abundant spore production occurs during wet leaf periods of at least 8 hours (including extended dew periods) and moderate temperatures of 60 to 80°F. The spread of the disease within a field can occur quickly. Long-distance dispersal is dependent on wind patterns and weather conditions and is the subject of current research.

When should I start scouting for soybean rust?

The timing of scouting will depend on your geographic location within the United States. Soybean producers in southern growing areas will need to begin scouting before their counterparts in more northern growing areas because of where Asian soybean rust is expected to overwinter.

In northern growing areas begin scouting in mid-July and continue through mid-August. Check the undersides of the lower leaves for a yellow mosaic discoloration and reddish-brown to tan pustules when leaflets are well- developed.

When should we start to spray the disease once it is found in our area?

Current research suggests that the first application should be applied at the initiation of flowering (R1). The second application, if needed should be applied 20 days later.

How many times do we need to spray in a season?

Based on current research, soybean producers will likely need to apply two to three applications of a fungicide to obtain optimal results.

In Brazil during the 2003-2004 season, it was estimated that 95% of the acreage was treated with between 1½ to 2 sprays. Short-season varieties only required one spray, while long-season varieties needed 2-3 applications.

How long will it take for the rust move from the south to the north?

Opinion varies on the time it will require for Asian soybean rust to reach its potential range after the initial introduction into the United States. It could take one season or several years.

Once established in the southernmost areas of the U.S., the spread of rust from south to north will be different each year. The movement will depend on the amount of inoculum that overwinters in the south each year and on spring weather conditions.

Is this an act of agro-terrorism?

No, the spread of soybean rust has been a natural event. There is no evidence of intentional introduction by humans.

Could this have been prevented? How?

No. As more land was planted into soybean around the world, the spread of soybean rust eventually came with it.

What steps will the state take to protect people and the environment in the rush to spray soybean fields with pesticides?

Close monitoring of environmental conditions (temperature and moisture) and the presence of P. pachyrhizi will provide the information needed to make informed decisions about treatment. These forecasting models are being developed, as well as communication plans, so that timely treatments can be made and unneeded sprays prevented.

Will insurance cover the losses caused by soybean rust?

When a producer is insured and follows good farming practices, losses attributed to disease, including Asian Soybean Rust, are often insurable. Soybean producers should verify their coverage with their insurance provider.

Can migrating birds carry rust spores to the United States?

No research has been done on this pathway; however the viability of spores that may travel in this way is being questioned. Environmental conditions required to keep the spores viable, such as temperature, too much moisture, UV light conditions and the oil found on bird feathers, and duration of the trip would greatly impact spore survivability. Also, the birds would have to be leaving South America at a time of the year when Asian rust spores are present.

Any suspected introductions of soybean rust should be immediately reported to:

Arrest The Pest Hotline.... 651-201-6684
Toll Free.... 888-545-6684
Invasive Species Program
Plant Protection Division