the overwintering pupae. Destruction of residues is also a means of controlling flea beetles.
the harvest of flue-cured types, shade-grown cigar wrappers, and several other cigar- tobacco types.
Populations of hornworms often are kept in check by parasitic braconid wasps and other beneficial insects. Parasitized worms are readily recognized by the presence of small white cocoons arrayed along their backs. If the majority of worms found are parasitized, further control measures should be avoided, if possible, to allow the parasites to hatch and continue working.
Tobacco also is attacked by the tobacco budworm (Heliothis virescens). Populations of this pest are suppressed through fall management of crop residues. Both bud- worms and hornworms are lepidopterous pests, vulnerable to formulations of the biopesticide Bacillus thuringiensis (Bt). To be truly effective, however, treatments must be made when the worms are small.
There are two primary harvesting methods: priming and stalk-cutting. Priming entails the picking of individual leaves as they come into their prime. Usually five to six pickings are required at five to ten-day intervals to complete harvest. Leaves may be strung on special sticks or handled in loose bulk form for curing. Priming usually results in higher total yields than stalk-cutting. It is used in
Stalk-cutting of tobacco is done by cutting the stalk at the base. In the case of burley and fire-cured types, the stalk is often split to hasten drying and to facilitate placement on wooden laths for curing.
Curing is the process of drying, chloro- phyll decomposition, and other natural chemical changes that result in the desired tobacco product. Proper curing is essential to quality. There are three primary forms of barn curing: air curing, flue curing, and fire curing.
All curing takes place in large, tight barns in which temperature and humidity are carefully controlled, usually through the use of ventilation and artificial heat. Air curing requires from four to eight weeks. Flue cur- ing entails the use of higher temperatures in the early stages of curing, which results in a lighter color. Fire curing utilizes natu- ral drying for the first three to five days, followed by the use of hardwood fires for higher-temperature drying, and to impart a characteristic odor and taste to the tobacco. Chewing-plug and snuff tobaccos are com- monly fire-cured.
Preparing tobacco to dry in a drying barn. Photo courtesy of USDA.