48th TWC, Tob. Work. Conf., 2018, abstr. 25

Chemically topping burley tobacco

University of Kentucky, Princeton KY USA

The act of topping tobacco (Nicotiana tabacum L.) involves the removal of the terminal bud or inflorescence of the tobacco plant. This practice ordinarily is accomplished by manually removing this top portion of each tobacco plant in an entire field, which is labor intensive and costly. There were several research objectives to determine the utility of a chemical topping system: 1) determine if burley tobacco could be chemically topped and simultaneously control subsequent sucker growth; 2) evaluate chemical topping compared to manual topping for yield and leaf quality; 3) examine currently registered suckercide products and appropriate application rates on efficacy of inflorescence termination and sucker control in burley tobacco; 4) distinguish ideal maturity groups of burley tobacco varieties that are better suited for chemical topping systems; and 5) determine the optimum plant growth stage at which chemical topping treatments can be applied. To pursue our objectives, studies were initiated to investigate the optimum timing of application, ideal maturity groups, and efficacy of suckercide applications using combinations of maleic hydrazide (MH), butralin, and fatty alcohols (FA). Our data suggests that chemically topping burley tobacco with a tank mixture of MH and a local systemic may be a suitable alternative as total yield and leaf quality grade index were not significantly different and total TSNA and MH residues were not significantly higher than with the standard manually topping system. The 10% button and 50% button application timings were best suited for chemically topping practices as treatments that target 10% bloom stages did not completely halt inflorescence growth but all application timings resulted in excellent sucker control. Medium and late-maturing burley varieties suffice for chemically topping methods, however, timing the suckercide application may be less difficult with later-maturing varieties. (Reprinted with permission)