Should emergence models for Lolium rigidum be changed throughout climatic conditions? The case of Spain

Abstract

Lolium rigidum Gaudin is a troublesome weed worldwide, and its distribution may increase due to climate change. It has become resistant to several herbicides and, therefore, its control is problematic. On the other hand, its seed biology, with little dormancy and short-term viability, can play a major role in reducing its seed bank, which would improve control of this weed. For this reason, knowledge of the emergence patterns of this species entails improvements for its management. In this work seeds from one population of L. rigidum, collected in Northeastern Spain, were distributed and sown in 11 sites across Spain, and its emergence was followed every 2–7 days for two growing seasons (2016-17 and 2017–18). These emergence sequences were compared with previously published thermal time and hydrothermal time based models, and new models were developed afterwards. The hydrothermal time based model did not significantly improve models based solely on thermal time. The accuracy of these newly developed models varied from site to site, but in general, they worked better for Northern locations than for Southern locations. Thus, the experimental sites were split between North and South, and specific models for each region were developed. The model developed for Northern sites worked very well, but the one for Southern sites needs improvement. This works reveals that, with regard to this weed species, probably different models should be developed for different climatic conditions. The model developed with data from Northern sites should be validated with local populations, while the one developed with data from Southern sites will probably need to be revised or newly developed with data from more Southern populations.