Abstract
The Phalaris genus includes annual weed species such as short-spiked canarygrass (Phalaris brachystachys Link.), little-seed canarygrass (Phalaris minor Retz.) and hood canarygrass (Phalaris paradoxa L.), which are especially problematic in Spain; as such, there is a need to develop models to predict the timing of their emergence. Field experiments were conducted at two different locations during two (2006/07 and 2007/08) and three (from 2005/06 to 2007/08) growing seasons. In both locations, 500 seeds of each Phalaris species were sown each growing season, simulating rain-fed cereal field conditions. In addition, the models were validated with three, four and eight independent experiments for P. brachystachys, P. minor and P. paradoxa, respectively. The emergence period of the three Phalaris species lasted between 31 and 48 days after sowing (DAS), showing two main flushes. The three cardinal points for parametric and non-parametric models were established to be between −1 °C and 1 °C for base temperature, between 9.8 °C and 11.8 °C for optimal temperature and between 21.2 °C and 23.4 °C for ceiling temperature; base water potential was estimated to be between −1 and −1.1 MPa. Both parametric and non-parametric models obtained similar results and were successfully validated in 12 out of 15 independent experiments.
Highlights
Phalaris is a grass genus that includes annual weed species that are spread through the Mediterranean basin area [1,2], India [3,4], China [5] and the United States [6]
In the case of P. brachystachys and P. paradoxa, seeds were harvested in June 2005 from a commercial wheat field near Jerez, Cadiz, in southern Spain (37.15 N, 6.18 W); whereas seeds of P. minor were collected from a commercial wheat field of Cordoba (37.86 N, 4.83 W)
When we compared the emergence of the Phalaris species to that of other problematic winter weeds in the south of Spain, we found that they were similar to that of winter wild oat (Avena sterilis subsp. ludoviciana (Durieu) Gillet and Magne), of which the emergence period lasts from November to March [31]
Summary
Phalaris is a grass genus that includes annual weed species that are spread through the Mediterranean basin area [1,2], India [3,4], China [5] and the United States [6]. In Spain, there are three Phalaris weed species: short-spiked canarygrass (Phalaris brachystachys Link.), little-seed canarygrass (Phalaris minor Retz.) and hood canarygrass (Phalaris paradoxa L.) [1]. These weeds are highly concerning in winter cereals crops [8,9], where yields can be reduced from 16% with densities of 50 panicles m−2, and up to 60% with densities of 900 plants m−2 [10,11,12]; these species can be problematic in some summer crops, such as sunflower [9]. Alcantara et al [8] demonstrated, for the Phalaris species, that the efficacy of herbicides is higher when optimizing the timing of chemical control, when it is possible to reduce the number of applied herbicides, and to reduce the application cost
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