The North American Plant Disease Forecast Center at North Carolina State University completes its sixth year of service to tobacco producers, industry, and extension services throughout North America. Information on the occurrence and location of new outbreaks is provided by a network of expert blue mold coordinators in each U.S. state, Canada, and Mexico. The forecasts are issued on the Internet three times each week from March through August. Additional forecasts are provided during peak epidemic periods. There is also a toll-free telephone "hot-line" that provides timely forecasts to growers without computers. Timely information on the geographic occurrence of blue mold and on the future movement of inoculum (fungus spores) across the North American continent is important to tobacco producers in managing this destructive and fast moving plant disease epidemic. Users find the maps, outlooks, and other information helpful in determining the time of arrival of spores and assessing the risk for their production areas. As always, we are interested in your comments on the system!
Blue mold occurred in most of the tobacco production regions of North America during the 2001 growing season. Reports were also received from the states of Texas, Illinois and Louisiana. No official report was received from South Carolina, despite the fact that blue mold was widespread over the nearby flue-cured growing areas of North Carolina. Wisconsin did not report any blue mold as well, though this is not unusual. Continental forecasting began on March 5 with disease sources in western Cuba and Mexico. A total of 459 forecasts were made on 74 days. The last forecast was made on August 31, 2001. Disease activity was still present in a few regions at that time. Of the samples submitted to the various laboratories for strain testing, all but one (from central Kentucky) were insensitive (resistant) to the fungicide metalaxyl. This is consistent with the experience of recent years, when metalaxyl-insensitive strains of Peronospora tabacina have dominated the yearly epidemics in North America.
The first report of blue mold in the United States was in northern Florida on March 19. Infections were discovered in plant beds in Alachua County. If the source of this outbreak were airborne inocula from the growing areas of western Cuba, the most likely time of arrival was March 1-3.
Blue mold was first reported in the flue-cured region of North Carolina on April 4, near the border of Wake and Franklin Counties. This outbreak occurred in a greenhouse, with infected transplants subsequently being taken to the field.
Blue mold spread slowly in the northern Florida and eastern NC source regions through the remainder of April and May. A common theme was for initial outbreaks to occur in greenhouses, with most field infections due to the setting of infected transplants. The weather was more unfavorable than not during this time, though some areas of North Carolina received copious rains in May. Nine counties had reported blue mold in North Carolina by the end of May.
The next initial outbreaks were bunched together between May 30 and June 1. Kentucky's first report was on May 30, in fields in western Clark and eastern Fayette Counties. Virginia's first report was from the flue-cured region in Dinwiddie County, on May 31. Reports of small field infections came from the southern Georgia counties of Echols and Ware on June 1. The Georgia and Virginia outbreaks were likely the result of short-range transport and deposition from Florida and North Carolina, respectively. Pennsylvania reported its first outbreaks on June 1. These outbreaks were the result of infected transplants shipped in from North Carolina. Lancaster and Chester Counties were the most heavily affected. Disease was also reported in Clinton and Lycoming Counties.
Three initial outbreaks were reported during June. The first report from North Carolina's burley region came from Madison County on June 18. Ohio's first outbreak, in Brown County, was reported on the same date. Maryland's initial reports came from Anne Arundel County on June 22. The NC burley outbreak could have come from eastern NC or from Kentucky. Inoculum from Kentucky was the likely source of the Ohio infection. Of the three outbreaks in Maryland, the most serious was the result of infected transplants from North Carolina. The other outbreaks were much weaker and appeared to be due to airborne transport.
The weather during June and July became more favorable for blue mold in most of the growing regions. By mid-June, 28 counties in the North Carolina flue-cured region had reported blue mold. Blue mold became well-established at low levels in Kentucky during June. During July there was a strong increase in activity, as plants reached the rapid-growth phase and the weather was frequently favorable.
Tennessee reported its first outbreaks on July 2. These occurred in Greene and Cocke counties in the northeast portion of the state. The first report in Virginia's burley area also came on July 2, from Washington County in the extreme southwest. Hampshire County, Massachusetts was the site of the initial outbreak in that state. This report was received on July 23. The Tennessee and extreme southwest Virginia outbreaks were likely the result of short-range transport from elsewhere in the southern Appalachian Mountains. Massachusetts' initial outbreak was probably due to airborne inoculum coming from Pennsylvania. Gallatin County, Illinois and Richland County, Louisiana were the initial outbreak sites for those states. Harrison, Jefferson, and Switzerland Counties in Indiana also reported blue mold in July.
The first report from Connecticut, in Hartford County, was received on August 7. Short-range transport from Massachusetts is the most likely scenario for this outbreak. The first report from Canada was received on August 23. This outbreak occurred in Norfolk County in southern Ontario. The blue mold in Canada was not expected to spread very much, however. Bottom halves of plants had already been harvested on most farms, and the weather in that region had been mostly unfavorable for disease development.
In 2001, blue mold was reported from most of the tobacco growing areas. Disease activity varied. Blue mold was most widespread in the Ohio Valley and North Carolina. Two events were most significant. One is the early introduction of blue mold into eastern NC, where the flue-cured crop had one of its worst epidemics in memory. The other is the shipping of infected transplants to Pennsylvania. Early stablishment of blue mold in these areas likely provided more opportunities for epidemic spread than have existed in other years.
A table of first reports from each state is given below.
This report represents a short version describing the 2001 North American blue mold epidemic. A more complete report will be available following detailed analysis of all disease reports, meteorological records, and state impact data. The complete set of day-by-day forecasts can be reviewed via the Internet website: http://www.ces.ncsu.edu/depts/pp/bluemold/.
The North American Blue Mold Forecast Center thanks all the reporting Coordinators for each US state and adjoining countries for their participation during 2001. If you wish to become part of the Forecast System, or need further information, contact C. E. Main or the Forecast Center directly.
First Reports of Blue Mold to the North American Blue Mold Forecast Center in 2001 (a)
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Alachua County, FL |
March 19 |
Cuba |
? |
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Wake / Franklin County, NC (flue-cured) |
April 4 |
N FL |
? |
|
Clark / Fayette County, KY |
May 30 |
Undetermined |
? |
|
Dinwiddie County, VA |
May 31 |
Eastern NC |
? |
|
Echols / Ware County, GA |
June 1 |
Northern FL |
? |
|
Lancaster / Chester County, PA |
June 1 |
Infected transplants |
? |
|
Madison County, NC (burley) |
June 18 |
Undetermined |
? |
|
Brown County, OH |
June 18 |
Kentucky |
? |
|
Anne Arundel County, MD |
June 22 |
Infected transplants |
? |
|
Greene / Cocke County, TN |
July 2 |
Southern Appalachian Mountains |
? |
|
Hampshire County, MA |
July 23 |
Pennsylvania |
? |
|
Hartford County, CT |
August 7 |
Massachusetts |
? |
|
Norfolk County, southern Ontario, Canada |
August 23 |
Ohio Valley |
? |