Emergence and early growth of Galium aparine and Galium spurium

Royo-Esnal A, Torra J, Conesa JA & Recasens J (2012). Emergence and early growth of Galium aparine and Galium spurium. Weed Research. 52, 458466. Summary With the aim of improving the control of Galium aparine and G. spurium, field experiments were conducted in a Mediterranean winter cereal field. Emergence and early growth (in number of whorls) of six populations of these weeds were examined. Populations were sown in November 2005 and 2006 with four randomised complete blocks in north-eastern Spain. Emergence was determined by counting and marking newly emerged seedlings weekly for 3 months and vegetative growth was evaluated for each marked seedling group using the expanded BBCH (Biologische Bundesanstalt Bundessortenamt and Chemical industry) scale. Linear regressions were successfully fitted to the growth, using degree days and hydrothermal time as factors. Growth pattern differed between both years, but not between both Galium species, when fitted to growing day degrees (GDD), but these differences disappeared when fitted to hydrothermal time (HTT). Despite disparity in the emergence pattern among populations, new whorl production followed similar patterns for each Galium species, which allowed development of a common model. Maternal factors may have affected emergence, but populations did not show differences in whorl development. This growth model is a new tool that may be used to improve the timing of weed control strategies for Galium species in winter cereal fields under a Mediterranean climate.