Since the vegetation period 1998/99 in Germany 8-10 field trials were carri
ed out for the examination of weed thresholds in systems with herbicide tol
erant winter oilseed rape against non selective herbicides. The field trial
s will be conducted over a three year period. Contents of the examination a
re the practicability of the weed threshold model, the advantages or disadv
antages of the system "herbicide tolerant winter oilseed variety - non sele
ctive herbicide" and an economical evaluation of these systems in compariso
n to systems with conventional herbicide application. The application of th
e non selective herbicides is carried out post emergence in autumn regardin
g weed thresholds and will be compared with an prophylactic application of
non selective herbicides, an usual application of conventional herbicides a
nd an early post emergence application of conventional herbicides in winter
oilseed rape regarding weed thresholds. The first one year results show th
e effectiveness of the existing weed threshold model in systems with herbic
ide tolerant winter oilseed rape varieties and non selective herbicides. Th
e results indicate advantages of these new systems because of a higher temp
oral flexibility for the application using non selective herbicides. An eco
nomical evaluation yet was not carried out.