Topping Height of High Leaf Potential Varieties

Grants and Contracts Details


he newer burley hybrids released by the Kentucky-Tennessee Tobacco Improvement Initiative (KTTII), 206LC, KT209LC and KT210LC, are considered to be "late-maturing" because flower buds develop about 10 days later than the older varieties (KY 14, K14 x L8) but produce six to ten more leaves. These new hybrids therefore have a high leaf number potential (HLP) compared to the low leaf number potential (LLP) older varieties. The Kentucky-Tennessee Burley Production Guide recommends that topping should be done when 10 to 25% of the plants are in flower leaving 22 to 24 leaves on the plant. An unknown factor about the effect of topping these hybrids very early is that anecdotally these high leaf potential hybrids can "hang on longer" in the field before they are harvested. This may suggest that they are slower to ripen in which case harvest may have to be delayed for longer than the conventional 28 days after topping. However, one very positive aspect of topping these hybrids early is that there is the potential for chemically topping which would considerably reduce the cost of labor. The concept of chemical topping is that bud is severely damaged by the application of either a local systemic dinitroaniline or systemic maleic hydrazide growth regulator, and the expansion of leaves less than about six inches long is also retarded and therefore do not develop to their full potential size. Previous attempts at chemical topping of the lower leaf potential varieties have been inconsistent because often less than the requisite 22 - 24 leaves have been saleable. With the higher leaf potential hybrids, several leaves can be sacrificed to the suckercide without reducing the number of saleable leaves. Tests comparing topping heights of 20 and 26 leaves were done prior to 2001 using varieties that included "early maturing" (KY 14 x L8), "medium-early" (NC BH129), "medium" (TN 90 and R610) and "medium-late maturing" (TN 97) ones. The economic benefit of topping high was variable but growers encountered handling and curing problems with the tall plants. In a test in 2013, two HLP varieties, KT 206LC and KT 210LC, were topped "early" at the same time as 25% of the LLP varieties were in flower and were topped to the same number leaves, or "late" when these HLP varieties were in 25% flower 10 days later. The stalk height of the early topped HLP hybrids was 12 inches shorter and very much easier to load and house and there was no detrimental effect on yield or quality, although the later topped treatments did have more tip grade as was expected. The 2014 test compared early and later topping of KT 210, but also the effect of topping later but down to 22 leaves. Apart from the yield data, the effect of the topping treatments on alkaloid content and quality are also important criteria that should be considered.
Effective start/end date2/1/156/30/16


  • Council for Burley Tobacco: $10,000.00


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