Determination of johnsongrass [Sorghum halepense (L.) Pers.] level of sensibilty to nicosulfuron

Abstract

In 2002, a johnsongrass population survived the application of ALS inhibiting herbicides in the locality of Zemun Polje, Serbia and Montenegro. This locality is known to have been treated with ALS inhibitors for years which may be considered the main cause of selection for herbicide resistance (R). The indices of resistance (IR=1.00 to IR=1.14) of the analyzed morphometric parameters show that no significant difference in susceptibility to nicosulfuron was found between the R and susceptible (S) populations. However, when a more sensitive method of monitoring ALS activity in vivo was employed, the index of resistance (IR=15.95) obtained by comparing enzyme inhibition in the two populations showed that nicosulfuron inhibited the enzyme in the S population of johnsongrass >15 times more than in the R population.