Climate change and decreasing herbicide persistence.

A herbicide degradation model, using real weather data for the period 1980-2001, has been used to estimate the change in persistence of autumn-applied isoproturon over this period. The results suggest that soil residues fell to the minimum for weed control on average approximately 30 days earlier over the last 5 years of this period than in the first 5 years, equivalent to a reduction of approximately 25% in the duration of weed control. This decline in persistence is attributed to increasing soil temperature. The results are discussed in relation to recent observations and predictions on climate change. The relevance of the findings to other pesticides and future weed control is considered.