April 19, 2005

Sentinel plots set up across US to detect soy rust

A network of sentinel plots is being set up across the United States and Canada to provide early detection of the Asian soybean rust. The plots are part of the National Soybean Rust Sentinel and Monitoring Network, a project of the US Department of Agriculture's Animal and Plant Health Inspection Service.

Asian soybean rust is caused by the fungus Phakospora pachyrhizi which has been moving westward from its centre of origin in China and has now reached North America by way of Brazil. The spores create lesions on the plant that look like rust.

According to plant pathologist Don Hershman of the University of Kentucky College of Agriculture, a sentinel plot is planted with an early maturing soybean variety in order to get the plants to canopy as quickly as possible, which encourages soybean rust development if the spores are in the area. The aim of a sentinel plot is to detect soybean rust if it is in the area as soon as possible, he said.

The sentinel plots will be planted 15 to 25 days before normal soybean planting times and monitored every three to seven days. If the rust spores are present, disease symptoms will appear first in the sentinel plots.

The early warning system will give farmers a longer lead time to make decisions on whether to spray fungicides to protect their plants before rust takes hold in their fields.

Soybean rust has been a devastating disease in many parts of the world, said agricultural experts. There are no commercial soybean varieties with resistance to the rust at this time. The only treatment is preventive spraying.

So far this year, soybean rust has been confirmed in two US counties, both in Florida. Locations in Mississippi, Alabama, Louisiana, Texas and Arkansas have been scouted, but no soybean rust spores have been found.