Photographer:

R.J. Reynolds Tobacco Company

Damage

Description:

Triazines are a group of herbicides which include atrazine, cyanazine, propazine, ametryn, prometryn, simazine, and metribuzin. Substituted ureas are a group of herbicides which include linuron, diuron, fluometuron, and chloroxuron. Both triazines and ureas produce similar injury symptoms. Injury can be caused by foliar or root uptake. Mild symptoms from low levels first appear on the tips of older leaves as yellowing between the veins. As the injury increases, the areas between the veins turn brown and progress toward the base of the leaf. The leaves will die back from the tips and edges. Plants will be stunted but may survive from very low levels; however, plant death will occur from high levels. Foliar exposure can kill the plant; however, with low levels, yellow to white areas are formed, turn brown, and fall out. Ureas may produce a brighter yellow to white leaf mottling than triazines. Symptoms of injury from all herbicides in the triazine and urea groups are very similar and are difficult to separate.

Field

Host:

flue-cured tobacco (Nicotiana tabacum (flue-cured type) L.)