Abstract

Solanum nigrum L. is a well-known weed in southern Sweden, especially in crops like carrots and celery with poor competitive effect, large row distances and lack of effective herbicides. It constitutes a special problem in cultivation of garden peas, since the fully-grown berries are difficult to separate from peas in the food processing industry. The seeds remain non-dormant until July, and consequently seedlings are emerging and need to be controlled during a long period by repeated mechanical or chemical treatments. Thus, it is of great interest to develop a model, which could predict at what date weeding could be terminated without the risk of harvested peas being infected by berries. Two experiments were conducted to test the hypothesis that temperature sum could be used to predict the phenology of S. nigrum. In experiment 1, seeds were germinated in petri dishes and subsequently sown in 1.5 L pots filled with soil consisting of 6 % clay, 11 % silt and 83 % sand. Fifteen pots, with one plant per pot, were placed in each of three climate chambers. The conditions in the chambers simulated changing temperature and photoperiod in southern Sweden during the period 15 April–15 July, 15 May–15 August and 15 June–15 September, respectively. Development stage of plants, according to a modified BBCH-scale, was registered every 2nd or 3rd day. Results showed that the phenological development from emergence to mature berries could be well described by a thermal time model. The first visible bud (stage 51) appeared at 343 day degrees (base temperature 3 °C) from sowing in petri dish. The first berries were visible (stage 71) at ca. 660 day degrees and reached full size (stage 89) at ca. 1100 day degrees. The differing climates did not affect the temperature sum required to reach a given development stage. In experiment 2, the development of plants was followed at four sites in the region of Skåne, southern Sweden. Individual plants, emerging at different dates from 15 May to 10 July, were marked and the development stage was registered weekly. Data was analysed using the temperature sum from development stage 11-12 (1-2 true leaves) to stage 51 (first buds) and stage 71 (first berries visible), respectively, in a regression versus time (Julian days) to stage 11-12). The number of day degrees to development stage 51 increased with time, but only at one site when analysing thermal time to stage 71. Thus, the thermal model overestimated the effect of high temperatures in mid-summer on the rate of development, especially from the two-leaves stage to the bud stage. For plants studied in the field the mean temperature sum from stage 11-12 to stage 71 was 576 day degrees, based on 109 observations and regional temperature registrations (base temperature 3 °C). This is to be compared with 520 day degrees for plants grown in the climate chambers when temperature sum was calculated from stage 11. In conclusion, the results from the climate chamber experiment imply that it might be possible to develop a thermal model, which could predict the phenology of S. nigrum. This would greatly benefit the cultivation of garden peas, by making it possible to reduce the number of herbicide applications. Also, in other crops it might be possible to predict the time for viable seeds to develop, and thus the need for weed control to avoid build-up of the soil seed bank. However, as indicated by results in experiment 2, further work with the model must take into account the overestimation of the effect of high mean temperatures on the phenology

Keywords

Nightshade; phenology; Solanum

Published in

Title: 14th EWRS Symposium, Hamar 18-21 June 2007
ISBN: 978-90-809789-2-8
Publisher: European Weed Research Society

Conference

14th EWRS Symposium

SLU Authors

• Andersson, Lars

  • Department of Crop Production Ecology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Agricultural Science


Permanent link to this page (URI)

https://res.slu.se/id/publ/15021