Aphids allowed to build up in an older crop can move to younger plantings carrying these viruses, unless controlled. However, there are some strains of each of these Poty-viruses for which little resistance or tolerance is imparted by the VAM genes, but fortunately such strains are not yet dominate. Tn 90, Ky 8959, Ky 907, NC 2, and NC 3. Other varieties with the VAM source of resistance are in the final stages of development. A number of researchers have developed burley tobaccos resistance to certain of these Poty-viruses using genetic engineering methods.
Some lines show promise, but regulatory steps prevent release of until further testing is completed.
Notice that varieties vary greatly in their extent of yield reduction and no variety is completely resistant to all three viruses. Prior to Being Knee-High in Kentucky Field Tests. The viruses are carried over in the living parts of these plants so it is important to eliminate or reduce these weeds where possible. The weeds closest to the tobacco field are the most important sources of overwintering. Planting of row crops surrounding tobacco greatly aids in virus control by eliminating the weedy hosts.