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ALERT: First rust on soybeans this year found in southeast Florida
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By Marilyn Cummins, Editor
StopSoybeanRust.com
6/16/2006 7:30 a.m. CDT Update -- The Florida state commentary posted on www.sbrusa.net this morning adds information about what Tropical Storm Alberto's impact may be on the soybean rust situation:
The commentary from 6:50 a.m. CDT today says:
"A soybean sentinel plot in south Florida (Martin County, near West Palm Beach) was confirmed positive by PCR. This plot was identified as being near a source of rust, so its early infection is not surprising. At this time no other sentinel plot in Florida is known to be positive, although several others are near known rust infestations.
"On June 11-13, Tropical Storm Alberto moved through Florida. Although the western panhandle was not affected, Tallahassee received 4 inches of rain, with more rain and wind toward Jacksonville. The direction of the storm path was toward the northeast, so if any spores were carried from Florida and the southeast, they would likely have ended up in the Eastern seaboard.
"With this said, we feel the overall production of rust spores in Florida is still very low due to our previously dry conditions; the spore load would probably be greater with storms later in the season. Following Alberto, the soils are saturated, and there is considerable fog and dew formation, providing further opportunity for rust to develop. If Alberto does have an impact on soybean rust, we expect it to be observed in the sentinel plots during the next few weeks. The Florida kudzu canopy is fully developed and flowering. All other soybean sentinel plots are still negative and at R1-R3 maturity stages.
"Most commercial soybeans are planted in Florida and are at early vegetative stages. It is time to plan on scouting for soybean rust in commercial fields. Plan your scouting to start when you reach R1 or when nearby infections are identified. You should have a management plan in place in case disease does develop in your region."
6/15/2006 5 p.m. CDT -- Florida officials have confirmed Asian soybean rust in three maturity groups of soybeans in a sentinel plot in Martin County. This is the first occurrence of soybean rust on soybeans planted this season anywhere in the U.S.
Carrie Harmon of the University of Florida told www.StopSoybeanRust.com there was a 29-percent incidence of rust in the plot, with the oldest infection being in the Group III soybeans. She said it then spread to the Group V and then the Group VII in a pattern similar to that seen in plots last year.
The samples were collected by a scout yesterday in the sentinel plot near West Palm Beach, Fla., and, since this is the first time for rust in this southeastern-Florida county, the spores were confirmed by PCR testing -- both conventional and real-time, Harmon said.
While she said this infection is not going to have a major impact on inoculum levels in the state, given how much lower those levels are compared to last year at this time -- this is the first positive rust find in the United States since rust was found on March 2, 2006, in Miller County, Georgia. That rust, on kudzu, was found to be growing again yesterday, also.
Harmon said she was not sure how much rain Tropical Storm Alberto dumped on Martin County, but she said there was an average of 3 inches of rain across the state during the storm. That still leaves a moisture deficit of 6 to 8 inches for the year, she said.
"The ground is saturated now, so we're having heavy fog and dew," she said. "That could lead to rust development, but it takes at least seven days" for the resulting infection to be visible. Scouts are and will be out looking across the state.
The county, which is three counties north of Miami-Dade, where rust was found on kudzu on Feb. 13 this year, is now red on the USDA rust observation map, and an alert e-mail went out at 4:10 p.m. CDT. (The official state commentary was posted on the site at the time of this writing.)
Source: Interview with Carrie Harmon of the Southern Plant Diagnostic Network and the department of plant pathology, University of Florida, Institute of Food and Agricultural Sciences; and www.sbrusa.net.
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