Nitrosamines are potential carcinogens formed by the nitrosation of amines during the curing and processing of various food crops. Previous research has indicated that nitrosation can be blocked if there are sufficient antioxidants (AOX) present to scavenge the nitrite molecules, and that plants treated with harpin proteins produce endogenous AOX. Perhaps the best understood nitrosamines are tobacco specific nitrosamines (TSNA). In 2004, 60 tobacco grower trials were established in Kentucky and Tennessee to determine which agronomic factors influence successful use of a harpin protein (Messenger®) at the grower level. Growers were assigned one of 3 protocols: 4 or 8 oz product/acre in 50 gallons of spray volume (280 or 560 gm/ha in 468 l/ha), or 4 oz/acre in 100 gallons spray volume (280 gm/ha in 935 l/ha). Trial management was the factor having the largest impact upon results. Other factors shown to impact results were planting date, spray volume, spray concentration, plant spacing, stick spacing in the barn, barn ratings, and seed source. Rate and spray dates and times did not appear to influence results. Results may apply to other crops with nitrosamine issues, or to crops in which enhanced AOX are desirable.