The total number of U.S. counties with Asian soybean rust in 2006 grew to 88 in the past seven days -- 18 new positive counties were reported in six states, with new rust also found in counties already "red" on the USDA map.
For comparison, at the end of the day Oct. 4 last year, there were 64 counties with soybean rust in only five states -- Alabama, Florida, Georgia, Mississippi and South Carolina, with only three new U.S. finds in the week prior to that date.
While in soybeans have matured past the point of using fungicides in many of the states with soybean rust, monitoring continues so that spread of the disease can been documented. Last year, soybean rust was discovered in 74 additional counties before the calendar year ended with a total of 138 positive counties in 2005.
Here's a detailed run-down of the soybean rust found this week in new counties and in more locations in known-positive counties. The states are in alphabetical order:
Alabama: First new rust on soybeans since February
These are the first reports this year of soybean rust on soybean in the state outside of Baldwin County -- where soybean rust was first found on Feb. 20 this year. All other finds had been on kudzu. Soybean rust was found again Sept. 26 in two commercial soybean fields in Baldwin County. Total rust counties: 7.
About 30 percent of the commercial soybean crop has been harvested. The majority of soybeans in Alabama are at the R6 growth stage or beyond.
Florida: Two new counties, several other finds
Total rust counties: 15.
"We are going into a dry period (usual for October) but the rust is still sporulating and spreading in infected areas," Florida officials said. "Most soybean growers in the panhandle of Florida should be at or beyond R5, except in late-planted fields. After R5, fungicide applications against rust do not increase yield. If crop is at R5 or earlier, growers should reevaluate the situation frequently."
Georgia: First soybean rust in commercial fields this year
The first site was a soybean sentinel plot located at a university station planted with DP 6568 soybeans that were at about the R8 growth stage. Twenty-one of 50 leaflets were infected with fewer than 10 rust pustules per leaf. The plot was plowed under after detection.
The second site was a commercial field in Toombs County approximately five miles from the sentinel plot. Eleven of 60 leaflets were infected in the commercial field with fewer than 10 rust pustules per leaf in determinate R7 soybeans.
"These finds in Toombs County came as no surprise, since rust had already been confirmed in Burke and Washington Counties and in South Carolina," the commentary said.
Total rust counties: 13.
"Rust development in Georgia seems to be slowed due to the drought that occurred the early part of this summer. With the recent finds in South Carolina and these finds in Toombs County, everyone still needs to be on alert for rust in our state as well, particularly for late-planted soybeans. Scouting still continues."
Louisiana: Two new counties brings state count to 18
As of Sept. 25, the commentary said, harvesting is about 80-percent complete. Some late-planted beans are in the mid- to late-range reproductive stages. Total rust counties: 18.
North Carolina: Rust breaks out in eight counties
This brings to 12 the number of counties positive for soybean rust: Sampson, Washington, Columbus, Robeson, Bladen, Brunswick, Scotland, Craven, Jones, Beaufort, Lenoir and Edgecombe.
Per the commentary, "In many instances it is too late to apply fungicides to soybean, and the chances of measurable yield loss from soybean rust are minimal!
"Little new infection has occurred recently in most of the state because of low temperatures when leaf wetness is high (early in the morning in most cases). Although rust probably got well distributed with recent wind and rain, weather forecasts are for lows in the low to mid 50s for the next five days. Spores on leaves require 6 hours of leaf wetness at temperatures from 60 to 80 degrees Fahrenheit for infection to occur.
"Some infection will undoubtedly still occur in limited areas of some fields where shade or other factors influence microclimate in the canopy. Still, it will most likely be three to four weeks before premature defoliation that will influence soybean yield will occur, and this will probably be in isolated areas of certain fields.
"Most soybeans will defoliate naturally over this period through the maturation process. Thus, the likelihood of a positive economic return from fungicide application is greatly reduced, even for late-planted soybean."
South Carolina: Two new counties with rust in commercial fields
Oct. 2: Rust has been found in a sample submitted from a commercial field in Saluda County. Two out of 25 leaves had several pustules present. There is no sentinel plot in this area.
Sept. 28: Today, rust was found in a sample submitted from Clarendon County. One out of 25 leaves had one pustule present. The commercial field is located near Manning and had been sprayed one week ago with fungicide.
The 18 counties in South Carolina with rust are: Aiken, Allendale, Anderson, Barnwell, Bamberg, Calhoun, Clarendon, Colleton, Darlington, Dorchester, Edgefield, Florence, Hampton, Horry, Lee, Orangeburg, Saluda and Sumter.
"The sunny, relatively cool days projected for the next week in South Carolina probably are not favorable for the development of rust since moisture will be limited," the commentary said.
As of Oct. 2, most Maturity Group 5 and 6 fields are near harvest. Most of the May-planted group 7 and 8 soybeans are past R6. Almost all fields including double-cropped fields are at least at R5 and rapidly approaching R6. "Therefore the number of fungicide sprays this week for rust should be minimal," the commentary said.
SOURCE: Article from StopSoybeanRust.com based on state commentaries on www.sbrusa.net; StopSoybeanRust.com archives.