Biological invasion is considered to be a major threat to biodiversity along with global climate change. Common milkweed (Asclepias syriaca L.) is a non-indigenous invasive plant species that has been invading large areas of sandy habitats in Hungary. This species hinders regeneration of sandy oldfields by inhibiting colonization and resource aquisition of natural species due to shading effects, high competitive capacity and allelopathic compounds. In 2006, we started an experiment to study the effects of herbicide treatment and search for appropriate restoration methods supporting regeneration processes after herbicide application. In July 2006, a non-selective herbicide (glyphosate) was applied to 3 sandy old-fields invaded heavily by A. syriaca near the strictly protected Fülöpháza Sand Dunes. Following herbicide application, different techniques (sowing of native grass species, sowing native grass and herb species mixtures and mowing) have been used to restore the vegetation. Preliminary results show that herbicide application seems to be an effective way to control common milkweed in the short term. However, in the longer term recovery of common milkweed is expected if no further treatments to be applied. Non-target vegetation was also heavily affected by herbicide control. Glyphosate relapsed the vegetation back into an earlier stage of succession where open patches were present before the treatment, while helped to proceed succession where the vegetation development was hindered by clonal grass species with phalanx growing strategy.
