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ALERT: First rust found in S.C. commercial field; furthest north yet
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8/15/2005 8 p.m. CDT -- Soybean rust has been confirmed in the southern part of South Carolina in a Hampton County commercial soybean field. This is the first confirmed rust in the state and becomes the northern-most county with rust in the country, just a bit north of Effingham County right across the border in Georgia.
Hampton County Ext. agent Tommy Walker collected the sample last week, and it was allowed to incubate before being examined on Saturday. John Mueller, Extension soybean pathologist with Clemson University, pegged it as rust and sent it to the Plant Problem Clinic for confirmation early Monday morning.
In Mueller's commentary (carried in full below), he said rust in the Hampton County field is at a low level and is doing very little damage to that field, while also not producing enough spores to immediately threaten nearby fields.
"However, it is evident that rust spores, most likely from Georgia or Florida, are being deposited in South Carolina fields," Mueller said.
South Carolina state commentary 8/15/2006:
Observations:
August 15: Rust was confirmed today in a sample collected last week from a commercial soybean field (R3/4)in Hampton County, S.C., by Tommy Walker, Hampton County Ag Agent. The sample was allowed to incubate for 2 days prior to examination Saturday by John Mueller, Clemson University Extension Soybean Pathologist. It was sent early Monday morning to the Plant Problem Clinic for confirmation by Meg Williamson, Clinic Diagnostician. Both confirmations were based on visual identification of the pustule and characteristic spores.
A second sample from a commercial field (R4)in Dorchester County collected by County Ag Agents Joe Varn and Marion Barnes strongly resembled the pustules from the Hampton County site; however, positive identification was not possible at this time since sporulation was not observed. Further analysis is being performed.
Eleven other fields in the Lower Savannah Valley were collected and examined last week. Two of these fields were within 100 yards of the affected field in Hampton County. No sign of rust was detected in any of those fields. Thirty leaves were examined from each of the fields. Only one leaf was found with rust from either of the fields. Less than five pustules were observed on either leaf. In the Hampton County field, rust is at a low level and is doing very little damage to the field it is in and not producing enough spores to immediately threaten nearby fields. However, it is evident that rust spores, most likely from Georgia or Florida, are being deposited in South Carolina fields.
Growth Stages:
Much of the full-season soybean crop in South Carolina is past flowering and pods are developing rapidly. Early planted maturity group 3 and 4 soybeans are near maturity. Soybeans planted behind wheat are still at the vegetative stage.
Management:
Many growers in the Lower Savannah River Valley have recently sprayed protectant fungicides for control of leaf, stem, and pod diseases. They should wait until their spray interval has expired, or rust in neighboring fields becomes severe, to apply a second spray. Application of a second spray will be dependent upon the development of rust in surrounding fields. At the low level of rust detected in Hampton County, it should be at least 10 to 14 days before rust could develop to a stage where damage is likely. Rate of development will depend upon environmental conditions at specific locations. Growers north of Santee and West of Barnwell County should continue to spray beans with high yield potentials as needed for leaf, stem and pod diseases. It should be 10 to 14 days before they need to start focusing their sprays on rust.
Forecast Outlook:
Temperatures the next 7 days are forecast to include lows in the low 70s. These temperatures along with high humidity readings and afternoon thundershowers will create a somewhat favorable environment for rust development. However, high afternoon temperatures may exceed the threshold for rust development.
Scouting Recommendations:
The levels at which rust have been detected so far in South Carolina are below those which a grower or consultant could reasonably be expected to detect rust. No distinctive symptoms were present on leaves, and the limited number of pustules would be difficult to detect even with a magnifying glass or hand lens. The best scouting growers can do is to keep up with reports from Clemson University and this Web page (www.sbrusa.net) on the development of rust in known fields and future discoveries.
Scouting Techniques:
Wait until you are told that rust in monitoring plots is at levels detectable with the naked eye, and then begin surveying your own fields.
Source: South Carolina state commentary on www.sbrusa.net" and past reports of confirmed sightings in Georgia and other states.
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