In the southern Upper Rhine region 3 mass proliferations of Isatis tinctoria L. were observed since
1978, the last in 2005. Long-term observations in the Kaiserstuhl revealed that such “waves” followed
a drought period and collapsed after 2 - 3 years. Because dyer's woad (also called German indigo) has
been an important crop plant culture-historically and today is known as a troublesome pest in North
America, in 2005 it was investigated phytosociologically and with regard to its monophagous beetles,
documented nearly 3 decades by trap captures.
A semiquantitative detailed mapping in the Kaiserstuhl showed dominance in the most xerothermic
southwestern and central part, and absence in the somewhat moister northeastern part. The qualitative
analysis of stands revealed high demands on soil aeration and temperature, as well as for light intensity,
thereby indicating weak competition. Moreover, it evidently shows poor dispersal ability. The coincidence
with the mass increase of monophagous beetles, especially Psylliodes isatidis, explains the rapid
decline of the population of Isatis. In a literature comparison Isatis tinctoria turned out to be, at least
in southern Germany, a weak character species of the Convolvulo-Agropyrion repentis, the only alliance
of the Agropyretea intermedio-repentis present here
