Control of rush (Juncus spp)- an expanding weed in grassland and pasture area in Western Norway

Life cycle study The aim of the study is to explore the life cycle of rush species from seedlings in three consecutive years. Effect of cutting on growth and development was also studied as well as the pattern of carbohydrate accumulation and storage in the two species. This is an important trait for mapping of weak stadiums in the life cycle. When reserves are at a minimum, the weed is weak and vulnerable for control measures and competition. The results show that the species flowers at the same time, in middle of June. Opening of the seed capsules starts in mid-August. Flowering and seed production consequently are spread over a long period. Results also show a distinct regrowth pattern of rush species, the highest values in spring, lowest in July-August and an increase again in autumn. The carbohydrate analysis correlated well with the results of the regrowth experiment. Sucrose was the principal reserve carbohydrate with maximum concentration in spring and minimum in mid-summer. Regrowth experiment The aim of the experiment was to study regrowth ability after cutting. Both rush species were cut at different times through the growing season and regrowth was recorded 6 weeks after cutting. Regrowth ability was strongly correlated with time of cutting. The finding of a reduced regrowth ability in mid-summer which indicate a distinct weak point in the rush life cycle may be useful for performance of treatments at right time and consequently for developing cost effective control measures of rush. Frost tolerance of the Juncus-species (soft rush and compact rush) In the study of effect of frost on shoot formation and survival, the hypothesis tested is: will milder winters without frost increase the growth and development abilities of the species? The results shows that both species have good frost tolerance until February. The species have good regrowth ability both in late autumn as well as in during winter / early spring, so in milder winters and longer growing seasons the Juncus-species may get an advantage compared with grass and clover. In periods with active growth e.g. early spring the study shows that even moderate frost incidents will reduce regrowth of the species. Compact rush appears to tolerate severe frost more than soft rush. This is in good agreement with that compact rush stop growing earlier in autumn than soft rush. Soft rush hence is more vulnerable to cold winter conditions. The conclusion so far is that compact rush profit less than soft rush on the mild winters because the latter grow faster and establish bigger tussocks and store more carbohydrate reserves during the growing season than compact rush. This may be one of the reasons that soft rush is most aggressive and wide spread of the two species. The results from these studies indicate that the two species are not particular frost tolerant in early spring and that milder winter with less frequent frost incidents partly may explain the expanding of these species. Control measures Mechanical control Mechanical treatments using brush saw during two growing seasons revealed that cutting of soft rush in late summer or autumn reduced the plants considerably, whereas cutting during spring or early summer had small effects. When the rhizomatous plant part was destroyed, no regrowth was observed. Pasture topper was less effective than the brush saw due to too much aerial stems left, it is however, a more effective equipment for larger areas. Chemical control The auxin herbicides MCPA and mecoprp had superior effect on the rush species compared to sulfonylurea herbicides and aminopyralid. Reducing reestablishment of rush from seeds when renewing leys It is important to gain knowledge on how and when rush establish when leys are renewed on infested areas. Results from a trial over three years showed that less rush plants established at high N- fertilizer level (230 kg N per hectare) than at low (130 kg N per hectare). Less rush also appeared when performing cross sowing compared to one direction sowing. Seed mixtures: Less rush appeared with standard seed mixture (without 20% rye grass) than when ryegrass was included. He reason might be that the ryegrass died due to insufficient winter hardiness with a following loss of competitive ability of the ley. Characterization of area with increased rush establishment. Soil samples from these areas were collected in 2013 and are now being analyzed. In addition, a model experiment was finished in spring 2014. The hypothesis tested was that increased precipitation and water logging strengthen the competition ability of rush compared to the pasture grass. The results supported the hypothesis.

Summary Soft rush (Jûncus effûsus L.) and compact rush (Jûncus conglomerâtus L.) have had an increasing success in the coastal parts of Western Norway, not only seen in low input leys but during the recent years also in intensively managed leys and pastur es. The rush growth seriously reduces the forage quality and is such hampering the meat and milk production both in conventional and organic agriculture. "Control of rush (Juncus spp.) - an expanding weed in grassland and pasture area in Western Norwa y" is a four year research project aiming to investigate the biology of soft rush (Jûncus effûsus L.) and compact rush (Jûncus conglomerâtus L.) to find targeted means, both organic and conventional, to control an increasing rush growth and such ensure a stable production of high quality fodder. This will contribute to leys and pastures of satisfactory quality in organic and conventional meat and dairy production in Western Norway as well as to maintain the agricultural landscape. This will be done by 1) identify ecological conditions for rush growth, 2) implement means for control of rush in conventional and organic agriculture and 3) perform biological study for optimal chemical treatment. The Norwegian agriculture will benefit from knowledge aquired in the project, both biology and growth conditions of rush as well as effects of climatic parameters. Measures of soil tillage and competitive ley seed mixtures will be available as well as appropriate herbicides. The project will be coordinated and lead by Dr. Jan Netland, Bioforsk Plant Health and Plant protection in collaboration with Bioforsk Vest Fureneset, The regional agricultural authority (FMLA), The Norwegian Agricultural Extention Services (LFR) and Norwegian sheep and goat (Norsk Sau- og Geit, NSG), all in the counties of Hordaland, Sogn og Fjordane and Møre og Romsdal.