Phytolacca americana and P. acinosa are invasive non-native species in Slovenia. Phytolacca americana is already widespread and its spread has accelerated in recent years while P. acinosa is still in its early stages of spread and is mainly found in urban areas. Mechanical removal is the most effective way of controlling and preventing the spread of Phytolacca species. As removing fruit from dug or cut shoots is very time consuming and increases the cost of removal we wanted to determine at what stage of fruit development the seeds are already germinating and if there is a risk of sowing when removing the plants. For the germination tests in petri dishes and soil, we collected different ripe fruits of both species. Experiments were made to determine the germination rate and viability of Phytolacca seeds. We also tested the effect of different storage methods and sulfuric acid treatment on seed germination. Furthermore, we also analyzed fruit ripening on a cut plant and found that fruits can also ripen on uprooted plants and shoots. We found that isolated seeds germinated better than seeds inside the pericarp in both species which is probably due to the autotoxicity of the plant. Mature seeds of P. acinosa germinated best after drying and storage at room temperature, both within the fruit and isolated. Seeds of P. americana also germinated well in several other situations. Since we have found that seeds from fruits in different stages of maturity can germinate, it is important that when removing both Phytolacca species, all clusters of fruits regardless of maturity should be harvested and removed from the site and properly destroyed to prevent further spread. Better seed germination rate of P. americana may be the reason for the greater distribution of this species in Slovenia compared to the P. acinosa. In order to control and prevent the further spread of both Phytolacca species we have prepared a protocol for the removal of P. americana or P. acinosa from nature or plantings, based on the results of the research.
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