By TIM THORNBERRY
Kentucky Correspondent

LEXINGTON, Ky. — The weather so far this season has gone from warm and dry to cool and wet, creating conditions that have many tobacco producers watching their plant float systems closely for disease.

Instances of target spot, collar rot and Pythium root rot are showing up across the state according to information from the University of Kentucky (UK) College of Agriculture.

“Growers need to watch their seedlings closely for any sign of these diseases so they can manage them if they develop,” said Kenny Seebold, UK extension plant pathologist. He also said overall plant conditions are good despite these instances of disease.

“Actually if you look at things in an overview, things look pretty good. We are seeing a few problems in response to the weather we have had, but you expect that when you have some frost, some hot days and a change to cool nights, and that will cause some stress,” he said.

For those concerned about problems, green lesions on plant leaves are generally the first sign of target spot, which will turn brown if untreated and can ultimately cause defoliation, slow maturity, damping off and possibly plant death.

Collar rot is caused by a fungal plant pathogen, notes the information from UK and can be identified by “small, dark green, water-soaked lesions appearing at the bases of stems. Evidence of the disease is most visible when clusters of infected transplants collapse, leaving holes, usually about the size of grapefruits, in the plant canopy.”

UK reported the “diseases likely came in around April 16 with a cold front that brought clouds and rain to the area. The following weekend provided the prime opportunity for those two diseases to thrive in greenhouses.”

While both target spot and collar rot are found during cool wet weather, the Pythium root rot likely got its start from the above normal temperatures experienced in late March and early April. The disease shows up in greenhouses once float bed water temperatures reach and rise above 72 degrees.

“The first symptoms of Pythium root rot tend to be yellowing and stunting of transplants in a well-defined area or areas of a float bay; however damping-off can occur in severe cases,” Seebold said. “During the outbreak, seedlings wilt and root systems decay to some degree.”

He added that as some signs of plant disease have arisen, it would be ideal if farmers could get their plants in the ground in a week or two, but if the area gets a lot of rain it could increase the threat of disease. The long range forecasts however, are still calling for dryer than normal conditions for the next two months. The exception may have been last weekend though, as the state saw heavy amounts of rain, the heaviest of the year so far with several inches falling in some areas.

But once the ground dries enough to get equipment into the fields, that moisture will be beneficial to the crop.

“In some ways you like to see a little bit of moisture put into the system. If you know you’re going into a dry time, you don’t want the ground to be soppy, but it’s not the worst thing in the world to be planting into ground that has some reasonably good moisture so you can give that crop a chance to get moving,” said Seebold. “When we get into a situation where we are planting into good soil moisture, but we’re not getting a lot of rains around planting time, that’s an ideal situation.”

For now, Seebold suggested that farmers check their plants as much as daily to look for the diseases, giving them air as needed and fertilizer, but not too much, and to use their county extension educators as a resource to find out what is going on around them and recommendations for control.