J. Michael Moore,
Editor

University of Georgia
Extension Agronomist-Tobacco

Topics for this week include:

- Georgia Weather
- Plant Production
- Tomato Spotted Wilt Virus
- TSWV in Plant Beds
- Actigard
- Blue Mold
- Actigard 2 
- Tobacco Barn Heat Exchanger Retrofits

GEORGIA WEATHER

Rains fell on much of Georgia last week and temporarily improved soil moisture, according to the Georgia Agricultural Statistics Service. They also helped improve irrigation ponds. The rains slowed fieldwork in some areas with rainfall ranging from 0.65 of an inch in Cairo to 3.25 inches in Alma. Even with rainfall occuring in Tifton on each of the previous three Sundays, the average rainfall lags 2.5 inches behind the normal for this time of year.

The rains delayed tobacco transplanting in some areas on Thursday of last week and on Tuesday of this week. Temperatures dropped to the upper 30s on Tuesday night, but have averaged 70 for daytime and lower 60s for the evenings during the last week.

PLANT PRODUCTION

Plant production and availability appears to be just adequate with no large oversupply of greenhouse or bed produced plants. Transplanting started in some areas two weeks ago, with most of the central portion of the production area really beginning to get into the field this week. Northern production areas, above I-16 are just now beginning to start transplanting. Approximately 35 to 40 percent of the crop will be transplanted by the end of the first full week in April.

TOMATO SPOTTED WILT VIRUS (TSWV)

Tomato Spotted Wilt Virus has reared its ugly head in plant beds across the production area and stand losses are beginning to accumulate in tobacco which has been transplanted for three weeks or more with 2 to 3 percent of the plants showing symptoms. Use of Admire 2F is almost universal in greenhouse produced plants, with less use (85%) in the transplant water applied to bed produced transplants.

TSWV IN PLANT BEDS

According to Dr. Bertrand, TSWV is appearing in plant beds all over GA. It began to show up 2 weeks ago. None has been reported in plant houses yet, but it can occur there. TSWV will be more common in beds because they are fully open.

There is no way to control TSWV in beds, so, massive, costly spray programs are not advised.

Plants showing symptoms do not seem to live long in beds. They can be easily sorted out as plants are pulled.

Plants not showing symptoms may be infected. These plants don't seem to survive long after transplanting though we lack specific data. We do have data to show using symptomless infected plants does not have much impact on the amount of TSWV that develops.

Nine percent is the highest we have ever found. These beds were running 2+ plants with symptoms per yd. Four percent is the second highest we have found visible. TSWV was scattered all over these beds, but not in any unusual amount. We have found beds with about 1 visible TSWV / yd. that were 0% infected in plants without symptoms.

ACTIGARD

Bayer Corporation has recently recommended the use of Admire 2F under a Section 2(ee) label for suppression of Tomato Spotted Wilt Virus in tobacco by impacting the thrips vector. The label recommends use of 1.0 to 2.8 oz. / 1,000 plants as a plant house tray drench, or 1.8 to 2.8 fluid oz. / 1,000 plants applied in transplant water. Higher rates are required in the tranplant water to achieve similar results to those resulting from the 1.0 oz. rate in plant houses.

Growers still transplanting tobacco are encouraged to use Admire and to follow the label directions for suppression of TSWV.

BLUE MOLD

Dr. Tom Kucharek, Plant Pathologist at the University of Florida, reports that systemic blue mold is occurring in Alachua County in a plant bed where blue mold was found earlier this season. Some of the plants from that plant bed were set in multiple fields and are expressing systemic infection as well.

Systemic infection can be recognized in the plant bed or field as plants which have the bud leaves distorted, sometimes with chloroses or necroses. With a knife, you can cut the bud and upper most stem and upper most petioles longitudinally and see reddish-brown to orange discolorations in the center pith or as linear streaks in the vascular system. Often the terminal bud is killed and multiple suckers are formed. Intensive desuckering may be required to train the plant back to one stem.

Spraying with fungicides WILL NOT alleviate this problem on those plants. Plants that have normal-appearing bud leaves will likely grow out of the systemic blue mold unless their progressive growth is

impaired. However, the common leaf spotting and yellowing caused by the blue mold fungus can be reduced with fungicidal sprays. At this time, all tobacco fields in Alachua, Columbia, and Union Counties should be sprayed with either Dithane DF or Acrobat MZ.

Unfortunately, repeated sprays 5-7 days apart will be required, especially as the canopy becomes larger and irrigation or rain promote favorable conditions for blue mold. Transplants, with blue mold, from Alachua County have been set in Columbia and Union Counties. At this time all plant beds in Florida should be sprayed with Dithane DF. Dithane DF and Carbamate are the only fungicides labelled for use in the plant bed.

Dr. Paul Bertrand, UGA Pathologist, has encouraged Extension Agents to monitor the Blue Mold Forecast Homepage

http://www.ces.ncsu.edu/depts/pp/bluemold/

for predictions of blue mold spore tranport across the Georgia production area. With Moderate to High Risk situations growers are encouraged to follow an Acrobat MZ spray program until the risk of infection is past.

ACTIGARD 2

We are told that the delay in labelling of Actigard is for an indefinite time. For Actigard to be effecive, it will have to be sprayed on plants where blue mold is less than 1% severity. Actigard will activate plant resistance somewhat but will not be curative. If and when Actigard is labelled, application may only begin after the plants have reached a height of 18 inchs.

TOBACCO BARN HEAT EXCHANGER RETROFITS

Two Tobacco Bulk Barn Heat Exchanger Retrofit Shows were conducted in Georgia on March 29 & 30 in Claxton and Hahira, respectively. There was excellent participation by the known vendors of heat exchangers with eleven companies represented. A small crowd in Claxton reflected the pretty weather of the day and the level of field activity in the area as many growers were completing the transplanting task. Rain throughout much of the area brought out a larger crowd in Hahira, with representation from Florida as well as Georgia.

A Tobacco Barn Burner Retrofit Field Day to be held from 4:00 to 8:00 pm on April 12, 2000 at the Eastern Carolina Agricultural Fair Grounds - Florence, SC. The Fair Grounds are located North of Florence on Hwy 301/76.

Heat exchangers are being marketed as an alternative to the direct fired curing systems currently in use as a means of avoiding the formation of nitrosamines in the curing tobacco. A proposed funding program worked out in early March to assist growers with the retrofitting of curing barns has yet to be activated and approved by all parties involved. Lack of funding support is resulting in limited adoption of this equipment. For more information on this program please refer to the following web site:

http://www.ustobaccofarmer.com/

Thank you for visiting the Georgia Tobacco Hotline, presented by the University of Georgia Extension Tobacco Team and brought to you by the makers of Orthene 97 granular insecticide with reduced dust and reduced odor.