Oct 21, 2009
Soybean Rust Found In Parana - The Earliest On Record
Author: Michael Cordonnier/Soybean & Corn Advisor, Inc.
Farmers in Parana in southern Brazil have been worried that the heavy rains that have fallen over the last several weeks might set the stage for an early outbreak of soybean rust (Phakopsora pachyrhizi). Their fears may be coming true with the announcement that rust was indeed found at the end of September on volunteer soybeans in the northern part of the state. The disease usually affects volunteer soybeans before it moves into commercial fields, but finding the disease this early in the growing season is very unusual. Normally, the first rust is reported on volunteer soybeans in Parana in mid-November and it doesn't appear in commercial fields until late December or early January.
Farmers in western Parana need to be especially alert because that is the area where the planting pace has been most accelerated with approximately 20% of the 2009-10 soybean crop already planted. Soybean rust's greatest impact on the soybean plant occurs when the plant starts to flower and set pods so Brazilian scientist are not recommending that farmers start spraying for the disease. They are recommending that farmers purchase their fungicides ahead of time and get prepared to start spraying their soybean fields as soon as the crop starts to flower.
Brazilian farmers and scientist have developed methods to combat the disease, but successful control still depends on the weather. The fungicides used to control the disease are contact fungicides, which means that they need to be reapplied every 25-35 days. The biggest concern for the farmers is that there might be adverse weather when it is time to reapply the fungicides. Heavy rains might leave the soil too saturated for ground equipment or frequent rains may keep the crop dusters on the tarmac. Either way, if soybean rust gets a foothold in the field, yield losses can be very significant.
In addition to Parana, the disease was also detected in irrigated soybeans in the state of Tocantins in August and on volunteer soybeans in the states of Goias and Mato Grosso do Sul in early September.