Determination of the common ragweed (Ambrosia artemisiifolia L.) resistance to the herbicide thifensulfuron

Cilj istraživanja bio je utvrditi indeks rezistentnosti ambrozije na herbicid tifensulfuron. Biljke osjetljive (S) i potencijalno rezistentne populacije ambrozije (R) tretirane su s linerano rastućim (0,5 – 64 x) za R i linearno padajućim dozacijama (2x – 1/64 x) tifensulfurona za S populaciju (x = 7,5 g a.t./ha) u BBCH 12-14 ambrozije. Rezultati ukazuju na značajnu razliku između učinka na S i R populacije. Vizualnom ocjenom oštećenja utvrđen je progresivan učinak herbicida na S populaciju kod posljednje ocjene (28 DNT), a kod R degresivan trend. Temeljem podataka o redukciji suhe nadzemne mase tretiranjem s linearno padajućim i rastućim dozama izračunata je dose-response krivulja rasta i procijenjena je doza potrebna za redukciju 50% nadzemne mase (GR50). Za S populaciju ona iznosi 0,25 g, odnosno 171,94 g za R populaciju. Indeks rezistentnosti izračunat je kao omjer između GR50 R i GR50 S populacije koji iznosi 687,76. Rezultati istraživanja potvrđuju rezistentnost ambrozije na herbicid tifensulfuron.The aim of the study was to determine the Common ragweed Ambrosia artemisiifolia L.) resistance index to the herbicide thifensulfuron. Plants of the sensitive (S) and potentially resistant Common ragweed population (R) were treated with linearly growing (0.5-64 x) for R and linearly drop-down doses (2x–1/64 x) of thifensulfuron for the S population (x = 7.5 g a.t./ha) in BBCH 12-14. The results indicate a significant difference in efficiency in the S and R populations. A visual assessment of the damage revealed a progressive effect of herbicides on S population at the last rating (28 DNT) and a degressive trend in R population. Based on dry aboveground mass reduction data, treatment with linearly falling and rising doses calculated the dose-response growth curve and the dose needed to reduce 50% of the above-ground mass (GR50) was estimated: 0.25 g for S and 171,94 g for the R population. The resistant index was calculated as the ratio between GR50 R and GR50 S of the population and is 687,76. The results of the study confirm the resistance of Common ragweed to the herbicide thifensulfuron