As tobacco producers begin the annual task of selecting varieties for the 2001 growing season, they'll have several new varieties from which to choose, says J. Michael Moore, University of Georgia Extension tobacco specialist.
Moore encourages growers to plant only a limited acreage of any new variety until more information and experience becomes available from a wider range of soil and climatic conditions.
The new varieties for 2001 include the following:
GL 737. This variety was developed by Gold Leaf Seed Company with medium to high resistance to black shank and medium resistance to Granville wilt. It is resistant to some races of Southern root-knot nematodes. GL 737 is susceptible to tobacco mosaic.
NC 297. Developed by North Carolina State University with a moderate to high level of blank shank resistance, NC 297 has low resistance to Granville wilt and is resistant to several races of root-knot nematodes and is resistant to tobacco mosaic virus.
NC 606. This variety was developed by North Carolina State University with moderate black shank and Granville wilt resistance, in addition to resistance to several races of root-knot nematodes.
Spt H20. Developed by Speight Seed Company in North Carolina, this variety has high resistance to black shank, high resistance to Granville wilt, resistance to tobacco mosaic virus and resistance to Southern root-knot nematodes.
Moore says farmers can be assured that any variety that is released has been thoroughly evaluated before seed are made available for commercial planting. However, each grower may have different requirements for the variety to be grown on his farm.
“Ease of growing and curing, disease and nematode resistance and market acceptance should be taken into account when selecting a variety,” says the agronomist. “Since disease and nematode infestations on a farm can seriously limit variety selection, farmers should attempt to keep their fields free of these problems. Crop rotation is necessary on most farms to reduce losses from soil-borne diseases and nematodes.”
Growers should not depend solely on varietal resistance to prevent losses from diseases and nematodes, he adds. “Crop rotations and appropriate chemicals should be a part of every tobacco program, no matter which variety is grown. In severely infested fields, there usually will be some loss to black shank with any variety.
“Chemicals are available to reduce black shank damage, but a three-year or longer crop rotation is a proven means of reducing black shank losses. Rotation among a group of black shank-resistant varieties will prolong the resistance of any one variety,” notes Moore.
This practice, he continues, is most valuable where crop rotations are shortest. Nematode-resistant varieties have resistance only to Races 1 and 3 of Southern root-knot nematode.
“Losses to peanut, Javanese and Race 2 or 4 of Southern root-knot nematodes have been increased by short-term rotations, by growing varieties resistant to Races 1 and 3 of Southern root-knot nematodes and by the improper use of nematicides,” he says.
Rotating tobacco with nematode-resistant crops and effectively using nematicides are essential to preventing losses to nematodes, says Moore.
Several agronomic characteristics may assist growers in the selection of a variety, he says. These include yield, quality, suckering habits, height, leaf spacing, leaf size and maturity. Some of these characteristics, he says, may be more affected by cultural practices than by varietal differences.
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