The North American Blue Mold Forecast Center at North Carolina State University completed its fourth year of service to tobacco producers, industry, and extension services throughout North America. The forecasts were issued on Monday, Wednesday, and Friday each week from March throught August. Additional forecasts were provided during peak epidemic periods. Timely information on the geographic occurrence of blue mold and the future movement of inoculum (fungus spores) across the North American continent was important to tobacco producers in managing this destructive and fast moving plant disease epidemic. Users found the maps and other information useful in determining the time of arrival of spores and assessing the risk outlook for their production areas. We are always interested in your comments on the system!
Blue mold occurred in all the major production regions of North America during the growing season of 1998. Continental forecasting began on March 2 with disease sources reported in western Cuba and Mexico. A total of 451 forecasts were made on 72 different days, culminating on August 21, 1998. These forecasts were the result of analyzing and evaluating the disease development potential of over 1200 individual spore transport events. The disease was still active in the Ohio Valley, southern Appalachian Mountains, southern Ontario, and southern New England. During the height of the blue mold epidemic in June and July, more than ten active and geographically distinct source regions of blue mold were being monitored and tracked for their disease risk potential to other target regions. Blue mold samples submitted to the various laboratories for strain testing were largely insensitive (resistant) to metalaxyl.
Blue mold was first reported in the United States on March 31st from Alachua and Columbia counties in northern Florida. Disease development in the area continued during April as approaching cold fronts brought favorable weather every three or four days. Blue mold was discovered in southern Georgia on the 20th and 22nd of April.
A significant event occurred during the middle of April when blue mold was reported in north-central Tennessee and south-central Kentucky. Based upon diagnosis and firsthand observation, these outbreaks were attributed to infected transplants from southern Florida. The ensuing local spread was from infected transplants distributed to growers in nearby counties. Additional reports of blue mold from growers and extension agents in this region continued to come in to the Forecast Center during following weeks. Most of these reports could be linked directly to infected transplants.
The movement of blue mold into the Southeast and the introduction of blue mold to the Ohio Valley region occurred from mid-April to May 10th during a month of generally favorable weather. Spread due to airborne spore showers was slow in the Ohio Valley region due to unfavorable nighttime temperatures. Blue mold continued to spread in the South as eight counties in southern Georgia reported active blue mold by May 4.
Following a weekend of highly favorable weather May 8-10, the next ten days were hot and mostly dry in all the southern and eastern growing regions. However, another period of mostly favorable weather began May 22 and lasted about a month. Temperatures in the target growing regions shifted to the optimum range (18C - 24C) for infection and disease development. During this interval blue mold was reported present in most of the remaining production areas in eastern North America.
Blue mold was reported May 22 in southern Indiana, western Kentucky, and the mountains of eastern and northeast Tennessee. East-central South Carolina reported disease on May 27 along with additional reports from central Kentucky. Extreme southwest Virginia reported blue mold on May 29. By June 1 the Center had reports from south-central Virginia and southeast Pennsylvania. Meanwhile, blue mold was increasing in the Ohio Valley.
The first report of blue mold from North Carolina came from the burley-growing area in the western mountains on June 3. New discoveries were reported in southern Maryland and southern Ontario, Canada, on June 8. This was followed closely by reports of blue mold in the flue-cured areas of eastern North Carolina on June 10. Repeated outbreaks of local and short-range disease development near existing sources continued to be reported. The explosive rapid-spread phase of the 1998 epidemic culminated on June 17, when blue mold was reported from Massachusetts. Connecticut growers reported blue mold on June 29 after a two-week period of favorable weather in the region.
The last ten days of June and the remainder of the growing season saw a change in the predominant weather patterns. Low pressure systems and fronts tended to pass through the more northern growing areas and move less frequently into the southern production areas. Variable, unsettled weather occurred in the northern production areas. Periods of dry weather alternated with periods of partly cloudy skies and occasional afternoon thunderstorms in the southern regions.
Since blue mold had already spread throughout the major production regions, there was a corresponding shift from interest in long-distance potential transport to outlooks related to localized spread. After late June in the south, blue mold slowed down or stopped in eastern areas of the mid-Atlantic states. The disease remained active in parts of the Ohio Valley and southern Appalachian Mountains which were subjected to showers. Extended periods of hot and dry weather suppressed disease activity. Epidemic activity continued unabated in southern Ontario and New England, where frontal systems were passing consistently and bringing favorable conditions. Ohio on July 10, Wisconsin on August 17, and Missouri on August 21 reported new occurrences of blue mold during this time. The Forecasting System was discontinued on August 21.
The 1998 blue mold season was very active. The long-term and widescale spread of the 1998 epidemic was greatly influenced by two factors: (1) two 30-day disease-favorable periods, from April 10 to May 10 and from May 22 to June 22, and (2) the inadviseable movement of infected transplants into the Kentucky/Tennessee/Ohio Valley region in mid-April. The combination of these two events set the stage for a two-pronged, long-range blue mold assault on the eastern North American production regions. The result was the occurrence and development of blue mold in every major production area before July 4.
This report represents a brief, preliminary description of the 1998 North American epidemic. A more complete report will be available following 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 1998. If you wish to become part of the Forecast System, or need further information, contact C. E. Main or the Forecast Center directly.
|
County/State |
Date Reported |
Probable source (b) |
Impact (c) |
|---|---|---|---|
|
Alachua and Columbia County, FL |
March 30 |
Cuba |
? |
|
Grady County, GA |
April 17 |
N Florida |
? |
|
South-central KY, north-central TN |
April 17 |
Infected transplants |
? |
|
Spencer County, IN |
May 22 |
TN/KY border |
? |
|
Clarendon County, SC |
May 26 |
S GA/N FL |
? |
|
Lee County, VA |
May 28 |
E/NE TN |
? |
|
Lancaster County, PA |
May 28 |
TN/KY border OR S GA/ N FL |
? |
|
Watauga County, NC (burley) |
June 3 |
TN/KY border OR E/NE TN |
? |
|
Haldimand-Norfolk County, Ontario, Canada |
June 7 |
S GA/N FL |
? |
|
St. Mary's County, MD |
June 8 |
S GA/N FL or S Appalachian Mtns. |
? |
|
Greene and Lenoir County, NC (flue-cured) |
June9 |
NE SC |
? |
|
Hampshire County, MA |
June 16 |
South-central VA |
? |
|
Tolland County, CT |
June 28 |
Massachusetts |
? |
|
Adams County, OH |
July 8 |
Kentucky |
? |
|
Rock County, WI |
August 17 |
Western KY |
? |
|
Platte and Buchanan County, MO |
August 21 |
Western KY |
? |
Web page last updated by Thomas Keever on 9 October 1998.