July 14, 2004 | By: Laura Skillman

Wet conditions, diseases and summer storms have plagued tobacco fields across Kentucky .

Tobacco is in all stages of growth. Some crops have been topped for several weeks, while others only went into the ground in the past few weeks.

For many growers wet conditions this spring meant delayed planting causing the loss of transplants due to stem rots and blue mold infections, said Bob Pearce, a tobacco specialist with the University of Kentucky Cooperative Extension Service . For crops that did get transplanted, heavy rains have resulted in some drowning and stunting over large areas in some fields.

“We know from past experience a wet start is bad for tobacco production,” he said. “Wet conditions early in the season significantly reduce root growth and leave the crop less tolerant of the dry conditions that often occur later in the season.”

Recent storms resulted in wind damage to tobacco in parts of Kentucky . In some instances the stalk was broken resulting in farmers having to try to salvage those crops, said Andy Bailey, Extension tobacco specialist at the UK Research and Education Center in Princeton . It is too late to reset but far too early for the tobacco to be mature enough to have good quality, he said.

Blue mold is causing problems in many areas of the state and in some communities is building to epidemic levels. A blue mold advisory exists for the entire burley production area. Blue mold has been confirmed in 65 Kentucky counties as of July 13, according to the Blue Mold Warning System, an educational program of the UK Cooperative Extension Service.

Warnings exist for all counties with confirmed cases of blue mold. Watch and warning areas have been expanded into western Kentucky following the discovery of activity in Todd and Christian counties.

Other diseases also are posing problems in Kentucky tobacco.

“The biggest thing we’ve been seeing is a lot more disease pressure, spotting diseases especially,” Bailey said. “Frog eye leaf spot is one that usually comes in late in the season after topping, but we’ve seen more of that this year early on. I’ve been seeing that for about the past two weeks or so, mostly in burley. It is not as critical in burley as it is in dark tobacco because it is often seen as a sign of maturity in burley, but this year that won’t be the case.”

Black shank also is causing problems in many tobacco patches in the commonwealth.

“I bet we’ve seen more cases of black shank in the past three weeks than we saw all last spring,” Bailey said.

Dark tobacco growers are at a particular disadvantage with black shank because of the lack of resistant varieties compared to burley, he said. Next year, there should be at least one new black shank-resistant variety available to dark tobacco growers.

Tomato spotted wilt virus, which is transmitted by thrips, also is being seen in larger amounts this year especially in burley, Bailey noted. Some fields are approaching 15 to 25 percent infection. There are some insecticides used for aphids that seem to aid in controlling thrips as well, and in fields where these were applied the virus is not as severe. 

In addition to diseases, problems at planting had many farmers working their ground in less than optimal conditions.  As a result, problems associated with soil compaction are likely to be seen, Pearce said.

The symptoms of soil compaction are similar to those of a wet start and include limited root growth, stunting, nutrient deficiencies and drought stress. Cultivating or plowing tobacco relieves compaction at the surface of the soil but does little to break up the deeper compaction that reduces rooting depth and makes the crop more susceptible to drought stress, he said.

Sidedressing with fertilizers and irrigation can help to lessen the negative affects of compaction. Phosphorus and potassium are generally held tightly to the soil and little is lost due to rains, however deficiency symptoms may occur due to the limited root growth. Sidedressing with a potassium containing fertilizer may help in those conditions.

“I’m seeing some of the most severe cases of temporary potassium deficiency that I’ve ever seen,” Bailey said.

However, for many crops, it may be too late to sidedress without equipment causing damage to leaves, he said. Usually, sidedressing should be done no later than six weeks after transplanting.

Some nitrogen may have been lost due to the rains and saturated soils but these losses generally are less than the grower imagines, Pearce said. If the normal practice is to sidedress with nitrogen, then in most cases no adjustment in nitrogen rates is needed. However, if all the nitrogen was applied prior to planting and the heavy rains, a grower may want to consider adding another 10 to 20 percent of the total amount of nitrogen to make up for the losses.

As the growing season progresses farmers need to remain vigilant to diseases, especially the blue mold situation across the state. Check with your county Extension office for more information.



Writer: Laura Skillman 270-365-7541 ext. 278
Source: Bob Pearce, 859-257-7125; Andy Bailey, 270-365-7541 ext. 240