<p>Poslednjih godina u balkanskom regionu pa i u Srbiji, zabeleņeno je ńirenje i invazivne korovske vrste Asclepias syriaca. Pretpostavlja se da je u Srbiju dospela iz susedne MaĎarske gde se dugi niz godina gajila kao medonosna biljka. Zahvaljujući alelopatskim osobinama i jakoj kompetitivnosti, ova vrsta ne dozvoljava regeneraciju starih peńčanih polja Najčeńće se javlja u zapuńtenim voćnjacima i vinogradima, na peskovitim terenima pored puteva i ņelezničkih pruga, nasipima, formirajući pri tom čiste sastojine asocijacije ili se javlja sa joń nekoliko korovskih vrsta ali uz apsolutnu dominaciju A. syriaca. Konstatovano je njeno ńirenje sa parloga na obradive povrńine na kojima obrazuje &bdquo;oaze&ldquo;, naročito u usevima pńenice, ječma, suncokreta, soje, u uljanoj repici, voćnjacima i vinogradima. Imajući u vidu sve negativne aspekte nekontrolisanog ńirenja A. syriaca na ruderalnim i poljoprivrednim povrńinama, ciljevi rada bili su praćenje ńirenja i izučavanje njenih biolońkih i ekolońkih karakteristika kao i utvrĎivanje mogućih načina za njeno suzbijanje. Populacija svilenice na teritoriji Vojvodine ima tendenciju ńirenja i ustaljivanja posebno uz puteve i vodene tokove. UtvrĎena je na skoro svim tipovima zemljińta u Vojvodini. Uspeva na zemljińtima od slabo do jako karbonatnih, kao i od slabo do jako humusnih. Podnosi zemljińta čiji je sadrņaj pristupačnih oblika fosfora i kalijuma ispod donje granice optimalne obezbeĎenosti zemljińta, ali i na zemljińtima gde je sadrņaj vrlo visok do ńtetan. Analizom biolońkog spektra sastojina ass. Asclepiadetum syriacae L&aacute;nikov&aacute; in Chytr&yacute; 2009, utvrĎeno je da su one hemikriptofitsko-terofitskog karaktera sa dominacijom hemikriptofita. Godińnja produkcija semena A. syriaca po m2 je od 1.336,53 do 10.109,61, a sa povećanjem gustine biljaka po jedinici povrńine smanjuje se produkcija plodova. Udeo semena svilenice u ispitivanoj zemljińnoj banci semena je vrlo nizak pa A. syriaca ne formira permanentnu banku semena. Dormantnost semena prekida se njegovim izlaganjem niņim temperaturama tokom nekoliko meseci a vlaga igra značajnu ulogu u povećanju klijavosti semena.<br />Alelopatska svojstva svilenice potvrĎena su ispitivanjem uticaja vodenog ekstrakta iz korena na klijavost semena kukuruza, soje i suncokreta u koncentracijama 0,05-0,1g suvemase korena po 1ml destilovane vode. UtvrĎena je i značajna osetljivost gajenog i divljeg sirka na primenjene ekstrakte. Od ekstrakata korena svilenice pripremljenih sa različitim rastvaračima, najveći inhibitorni uticaj na klijavost semena soje imao je butanolni, a na klijanje semena gajenog sirka etil-acetatni i butanolni ekstrakt. Isto je i sa divljim sirkom i ńtirom, dok na klijavost semena kukuruza i soje ni jedan primenjeni ekstrakt nije imao negativan uticaj u značajnijoj meri. Ogledi u poljskim uslovima pokazali su uticaj alelohemikalija iz korena A. syriaca na redukciju prinosa kukurza i sirka. Vodeni ekstrakt korena u koncentraciji primene 0,04g/ml umanjio je prinos kukuruza za 10-15%, krmnog sirka za 12,5% a sirka metlańa za 23%. Ispitivanja mogućnosti hemijskog suzbijanja A.syriaca u poljskim uslovima pokazali su najveću efikasnost herbicida na bazi glifosata, 2,4-D i tembotriona. kao i nakon trogodińnje primene bentazona, bentazona + dikambe, a najmanja efikasnost ustanovnjena je prilikom primene dikambe. Terbutilazin i klomazon u većim preporučenim količinama primene efikasno suzbijaju svilenicu iz semena ako se herbicidi primene pre nicanja, dok imazamoks i oksasulfuron efikasno suzbijajuu tek iznikle biljke svilenice kada se u preporučenim dozama tretiraju biljke u fazi 2-4 lista.</p> / <p>In previous years in the Balkan region, including Serbia, spread of invasive weed species Asclepias syriaca L. was recorded. It supposedly arrived to Serbia from neighbouring Hungary, where it was grown as honey plant. Due to allelopathic properties and strong concurrence, this species does not allow regeneration of old sand fields. It is most common in neglected orchards and vineyards, sandy terrains along roads and railways, embankments, where form pure A. syriaca association, or several additional weed species occur, but with absolute dominance of this weed. From uncultivated areas on which it forms &quot;oasis&quot; its spread was noted especially in wheat, barley, sunflower, soybean, rapeseed crops, in orchards and vineyards. Considering all negative aspects of uncontrolled spread of A. syriaca on ruderal and agricultural areas, the aims of the paper were monitoring of its spread and the study of biological and ecological properties, as well as the establishment of possible ways of its control. On the territory of Vojvodina, common milkweed population has a tendency of spread and colonization, particularly near roads and water flows. It is established on almost all soil types in Vojvodina. It grows on poor to very calcareous soils, as well as on poor to very humic ones. Common milkweed withstands soil with the content of available forms of phosphorous and potassium below the optimum , but also the soils with high to damaging content of these elements. The analysis of the biological spectrum of stands of ass. Asclepiadetum syriacae, L&aacute;nikov&aacute; in Chytr&yacute; 2009, established that it is hemicryptophyte and therophytein, with a domination of hemicryptophytic character.<br />Annual seed production of A. syriaca seed per m2 is from 1.336,53 to 10.109,61, and with the increase in plant density per unit area, production of fruits is reduced. The share of milkweed seed in soil seed bank is very low, and therefore A. syriaca does not form permanent seed bank. Seed dormancy is stopped by its exposure to lower temperatures for several months, and moisture has an important role in the<br />increase in seed germination. Allelopathic properties of common milkweed were confirmed by examination of root water extract effects on maize , soybean and sunflower seed germination at concentrations of 0.05-0.1g of dry root weight per 1ml of distilled water. Significant susceptibility of cultivated sorghum and Johnson grass to the applied extract was recorded. From common milkweed root extracts prepared by various solvents, the highest inhibiting effect to soybean seed germination had butanol extract, and to germination of seed of cultivated sorghum, ethyl acetate and butanol extract. It was the same with wild sorghum and redroot pigweed while none of the applied extracts had significantly negative effect on maize and soybean germination. In field trials, allelochemicals from A. syriaca root reduced maize and millet yield. Root water extracts at the applied concentration of 0.04g/ml reduced maize yield by 10-15%, of fodder sorghum by 12.5% and broomcorn by 23%. In studies regarding chemical control of A.syriaca in field conditions,the highest efficiency was recorded for herbicides based on glyphosate, 2.4-D and tembotrione, as well as for bentazone and bentazone + dicamba after tree-years long application.Dicamba was recorded as the least efficient. Terbuthylayine and clomazone herbicides in pre-emergence application at higher label rates efficiently control common milkweed from seed, while imazamox and oxasulfuron applied at lable rates efficiently control young plants of common milkweed at the phase of 2-4 leaves.</p>

No description available.

The eastern migratory population of monarch butterflies (Danaus plexippus plexippus) has declined by >80% within the last two decades. One possible cause of this decline is the loss of >= 1.3 billion stems of milkweed (Asclepias spp.), which monarchs require for reproduction. In an effort to restore monarchs to a population goal established by the US Fish and Wildlife Service and adopted by Mexico, Canada, and the US, we developed scenarios for amending the Midwestern US landscape with milkweed. Scenarios for milkweed restoration were developed for protected area grasslands, Conservation Reserve Program land, powerline, rail and roadside rights of way, urban/suburban lands, and land in agricultural production. Agricultural land was further divided into productive and marginal cropland. We elicited expert opinion as to the biological potential (in stems per acre) for lands in these individual sectors to support milkweed restoration and the likely adoption (probability) of management practices necessary for affecting restoration. Sixteen of 218 scenarios we developed for restoring milkweed to the Midwestern US were at levels (>1.3 billion new stems) necessary to reach the monarch population goal. One of these scenarios would convert all marginal agriculture to conserved status. The other 15 scenarios converted half of marginal agriculture (730 million stems), with remaining stems contributed by other societal sectors. Scenarios without substantive agricultural participation were insufficient for attaining the population goal. Agricultural lands are essential to reaching restoration targets because they occupy 77% of all potential monarch habitat. Barring fundamental changes to policy, innovative application of economic tools such as habitat exchanges may provide sufficient resources to tip the balance of the agro-ecological landscape toward a setting conducive to both robust agricultural production and reduced imperilment of the migratory monarch butterfly.