Asian soybean rust has been confirmed for the first time this year in North Carolina, in Columbus County on the border with South Carolina. The find joins two more in Georgia and another in Louisiana since Tuesday.

This raises the number of states with rust this year to eight, in 54 counties and parishes. Last year at this time, there was rust in 58 counties in only five states: Alabama, Florida, Georgia, Mississippi and South Carolina. The additional states with rust at this point in 2006 are Louisiana, North Carolina and Texas.

Georgia also reported rust in Cook County today and in Sumter County on Tuesday, the same day Louisiana reported rust in commercial field in Washington Parish.

First North Carolina find; spray recommendations detailed

According to the N.C. state commentary on, "Asiatic soybean rust was identified on soybean samples collected from a mobile sentinel plot on 13 September, 2006. A few pustules were found on several leaves.

"The soybean leaves were collected from near Tabor City in Columbus County. Columbus County borders on South Carolina and is about 50 miles from Myrtle Beach, S.C.

The report from Steve Koenning and Jim Dunphy said 91 percent of the soybean crop in the state has set pods, "thus about 85 percent to 95 percent of the crop is no longer at risk.

"Soybean producers in the southern counties of North Carolina should be alert for rust moving any closer. If rust gets within 100 miles, and the soybeans do not yet have fairly good-sized seeds in the pods, we suggest spraying with a strobilurin fungicide. Assuming that some growers may not get into the field before mid-week after the rain, consider a combination of a strobilurin and a triazole (Headline SBR, Stratego, or Quilt) especially on late maturity (Group VII or VIII) and/or late-planted soybean.

"Soybeans that have full-sized soybeans in the pods (stage R6) before rust is identified in the field will probably mature before rust causes significant yield loss, and it is illegal to spray any of our fungicides that late in soybeans' development. As infrequently as rust affects soybeans that have not started blooming, we also would not spray soybeans that have not started blooming yet."

More rust in Georgia; Kemerait outlines spray guidelines

Georgia reports on that "Soybean rust was reported 9/13 in an industry research plot in Sparks in Cook County Georgia. This is the first report of rust in that county this growing season. Cook County is located in south central Georgia, south of Tift County Georgia. Rust has already been confirmed in Tift County, so this report in Cook County is no surprise."

On Sept. 12, soybean rust was detected on a soybean sample collected Sept. 18 from one of the sentinel plots in Plains, GA (Sumter County, located in west Georgia). Rust was detected with a dissecting microscope on one leaflet of 100 collected, with fewer than 20 rust pustules on the leaf. This is the first find of rust in that county this growing season.

"With the recent rains and the numerous findings of rust in South Carolina, it is extremely important that everyone continue to scout their soybeans for possible rust and be prepared to spray if you have not done so already," the report said. "If you are a soybean grower in Georgia, please follow the management recommendations given by Dr. Bob Kemerait given below:

"Spray guidance: It is likely that most of the commercial soybean crop in Georgia is now in the R4 (full pod stage) and may be moving to the R5 growth stage (early seed) where seeds are ~1/8 inch in length.

Theoretically, the soybean crop is at risk to Asian soybean rust until it reaches R6 (full seed) growth stage. Here are our recommendations:

"1. For growers whose crop is from R2 (full flower) to R4 (full pod), we recommend that a fungicide application is warranted for Asian soybean rust in all but the extreme northwest corner of the state (northwest Georgia should continue to monitor for rust). Growers whose crop is between R2 and R4 should use a triazole fungicide (such as Folicur, Domark, Laredo, Uppercut, etc.) or combination of triazole/strobilurin (such as Headline SBR) if infection has likely occurred in their field (e.g. SW Georgia and they have decent yield potential.

"Where it is unlikely that infection is established in a field, or that infection is very low, growers can effectively use any of our labeled products for control (strobilurins, triazoles, strobilurins + triazoles). Use of chlorothalonil must be considered carefully at this point. Our data suggests that chlorothalonil products do not perform as well as other products where disease infection may have already occurred.

"2. If the crop has reached the R5 growth stage in a field, the crop is still technically at-risk to soybean rust. However, given the slow spread of the disease until now, it seems unlikely that soybean rust will severely affect this crop before it reaches R6 (full seed). For growers who are concerned and wish maximum insurance, follow the spray recommendations above. However, we do not have a general spray recommendation for soybeans that have already reached the R5 stage and where rust is not yet found."

Louisiana count grows to 10 with new find

Louisiana reported 9/12 on that "Asian soybean rust was found in Washington Parish in a commercial field of soybeans. Although this sighting is the first for the parish, the crop is in the late stages of development. No treatment is required."

SOURCE: article by Marilyn Cummins, editor, based on Georgia, Louisiana and North Carolina commentaries on and archives.