Phenological and demographic behaviour of an exotic invasive weed in agroecosystems

Abstract

An experimental work was conducted in Lleida (Spain) aiming to characterise the phenology and to quantify the demographic processes regulating the populations of Abutilon theophrasti Medicus in maize fields. Seedling emergence started a few days after crop sowing in early May and continued during two more months. The vegetative phase was very long due to the late seeding emergence; these later emerged plants showed a slower development, and many of them did not reach the fertility stage. A flowering peak was observed 12 weeks after emergence in late July, and fruit dehiscence and seed setting started in mid August, several weeks before crop harvest. Four different cohorts were identified, and two main peaks of emergence were determined 21 and 49 days after crop sowing nearest related with field irrigation. A functional logarithmic relationship between cumulative growing degree-days (GDD) and cumulative emergence was also described. The resulting demographic diagram reflects greater values relating to seedling survival for May cohorts (90.2 vs 7.9%), to fertility (100 vs 75%) and to fecundity (3774 vs 92 seeds pl )1 ) than those determined for the June cohorts. The late emerged plants are subjected to a high density and are strongly affected by light competition, and their reproductive phase initiation delay is of about 10-20 days. In an assay conducted in Petri dishes, the seeds provided from plants emerged earlier were found more vigorous and germinated more than those from late emerged plants, which seem to be affected by incomplete fruit and seed ripening. Following the crop cycle without any weed control, the population rate increase was about 21.2. These values explain the high invasion capacity of this weed in the local summer irrigated fields, which consists in assuring their presence through a persistent soil seed bank and increasing the probability to spread to other fields.

Integrating measurements of seed availability and removal to estimate weed seed losses due to predation

“…Studies on the timing of weed seed shed are rare, and to our knowledge, no studies have ever checked whether the timing of seed shed has indeed changed over time. In climates that allow prolonged seedling emergence, seedling cohorts may differ in the timing of seed maturation (Recasens et al 2005). Selective pressure by seed predators may be one of the mechanisms by which the persistence of late emerging and maturing cohorts can be explained, despite lower quantity and quality of seeds produced by these cohorts.…”

Estimation and Comparison of Base Temperatures for Germination of European Populations of Velvetleaf (Abutilon theophrasti) and Jimsonweed (Datura stramonium)

“…Velvetleaf and jimsonweed are common and competitive annual weeds in summer crops worldwide. These two species are of great economic importance in several European countries (Danuso et al 2012;Recasens et al 2005). The seeds of velvetleaf are characterized by a physical dormancy due to an impermeable seed coat that prevents imbibition and, consequently, germination (Dorado et al, 2009a;Winter 1960b).…”

Experiencia en el control de malas hierbas invasoras en Cataluña desde el punto de vista de su gestión. Revisión Bibliográfica

“…Previamente, se había tenido experiencia con el comportamiento de dos especies invasoras como Abutilon teophrasti Medik. (Recasens et al, 2005) y Hetheranthera reniformis Ruiz & Pav. (Llenes et al, 2006), que se habían adaptado perfectamente a las condiciones climáticas y a los cultivos de Cataluña, obligando a cambiar sustancialmente su manejo, pero sobre las cuales no se realizó ninguna actuación desde la administración competente más allá del asesoramiento a los agricultores para su control, realizado por el Servicio de Sanidad Vegetal.…”