Nicosulfuron:Mode of Action

Nicosulfuron is recommended as a post-emergent selective herbicide for controlling a wide range of both broadleaf and grass weeds in maize. However, the herbicide should be sprayed whilst the weeds are at the seedling stage (2-4 leaf stage) for more effective control.

Uses 

Nicosulfuron controls annual grass weeds, broad leaved weeds, and perennial weeds such as Sorghum halepense and Elymus repens at rates of 30–60 g a.i./ha.

Phytotoxicity 

Nicosulfuron has excellent selectivity to corn. In cases where corn is stressed, nicosulfuron may cause yellowing of corn foliage; however, it is transient and does not affect yield.

Mode of Action

Plant Uptake 

Nicosulfuron is rapidly absorbed by leaf tissue and is translocated meristems via the phloem and xylem. Nicosulfuron controls weeds by inhibiting acetolactate synthase (ALS), also called acetohydroxy acid synthase (AHAS). ALS is a necessary enzyme for the production of three branched-chain amino acids, isoleucine, leucine, and valine. 

Symptoms 

Weeds treated with nicosulfuron will rst begin to develop chlorosis in the new growth and then gradually, as the weed continues to be starved of the vital branched-chain amino acids, the chlorosis symptomology will develop in older growth. Chlorotic symptomology then turns to necrosis and desiccation of the plant tissue occurs. Control typically takes 3-4 weeks, from treatment to plant death. 

Selectivity 

Nicosulfuron’s excellent selectivity to corn is due to the ability of corn to metabolize nicosulfuron into inactive metabolites.