the efficacy of herbicides for control of mowed plants of common ragweed (Ambrosia artemisiifolia L.)

Namen raziskave je bil ugotoviti, ali je možno ambrozijo uspešno zatirati na način, da košnjo in aplikacijo herbicida izvedemo hkrati. Za določitev učinkovitosti herbicidov nanesenih na rastline ambrozije takoj po košnji smo izvedli lončni poskus z več dejavniki. Prvi dejavnik je bila vrsta herbicida, drugi višina ambrozije ob košnji in tretji delež omočene listne površine s herbicidi. Rastline ambrozije gojene v loncih z volumnom 10 l smo v različnih stadijih (20, 35, 60 in 80 cm višine) s škarjami odrezali na višini 5 cm od tal. Rez s škarjami je bila simulacija košnje. Na preostanek rastlin smo nanesli herbicide na podlagi aktivnih snovi glifosat (1500 g/ha), dikamba (385 g/ha), bentazon (1200 g/ha) in tifensulfuron (12 g/ha) na način, da smo pri različnih obravnavanjih s herbicidno brozgo omočili 10, 35, 60, 85 ali 100 % površine listov, ki so ostali po rezi. Različne deleže poškropljene površine smo dosegli s prekrivanjem rastlin s plastično folijo tako, da je bil del listov prekrit, del pa ne. Učinkovitost herbicidov smo ocenili glede na maso suhe snovi, ki so jo oblikovale rastline v obdobju od maja do septembra in glede na količino semen, ki so jih uspele oblikovati. Učinkovitost herbicidov je padala z višanjem ambrozije ob izvedbi rezi in z zmanjševanjem deleža površine listov, ki smo jo omočili s herbicidom. Tudi interakcija med omenjenima dejavnikoma je bila statistično značilna. Rezultati kažejo, da sta za zatiranje ambrozije na način, ko ob košnji izvedemo hkrati aplikacijo herbicidov, primerna predvsem herbicida glifosat in dikamba, herbicida bentazon in tifensulfuron pa sta manj učinkovita. Zadovoljivo učinkovitost pri zatiranju ambrozije z uporabo glifosata in dikambe (več kot 90 % zmanjšanje zelene gmote in števila oblikovanih semen) je mogoče doseči, če rastline ob košnji ne presegajo višino 20-30 cm in s herbicidom omočimo najmanj 40 % površine listov, ki ostanejo po košnji.The purpose of research was to find out if it is possible to control common ragweed successfully with simultaneous mowing and herbicide application. For the determination of the herbicide efficacy we carried out pot experiment with several studied factors. First factor was type of herbicide, second was height of ragweed at mowing and third factor was part of leaf area moistened with herbicides. Plants of ragweed grown in pots with volume 10 l were cut off with scissors at height 5 cm above ground. Plants were cut off in different stages (at heights of 20, 35, 60 and 80 cm). Cut with scissors was simulation of mowing. On the remains of plants after cutting herbicides based on active substances glyphosate (1500 g/ha), dicamba (385 g/ha), bentazone (1200 g/ha) and thifensulfuron (12 g/ha) were applied in such a way that 10, 35, 60, 85 or 100 % of leaf area was moistened. We reached different ratios of moistened leaf area with covering plants with plastic foil in a way that a part of leaves was covered and part was not. Efficacy of herbicides was established on the basis of mass of dry matter which was formed by plants in period from May to September and on the basis of quantity of seeds formed by plants. Efficacy of herbicides decreased with height of ragweed at cutting and with decreasing of portion of leaf area we moistened with herbicide. Also interaction between mentioned two factors was statistical significant. Results showed that for efficient control of ragweed with simultaneous mowing and herbicide application herbicides glyphosate and dicamba are appropriate, but herbicides bentazone and thifensulfuron are not. Sufficiently high efficacy on common ragweed using herbicides glyphosate and dicamba (more than 90 % reduction of green mass and number of formed seeds) can be achieved if ragweed plants do not exceed height of 20-30 cm at mowing and, if at least 40 % of leaf area that remains after mowing is moistened by herbicide spray