Technical


emergent riparian weeds. Submerged weeds can be


controlled in water deeper than about 1.2m by using blue dyes to absorb the red light which plants use for photosynthesis. Floating algae can be controlled by using bacterial sachets that compete with the algae for nutrients, or by the use of hydrogen peroxide generating compounds, which oxidise the algae and kill it off. Dr Newman says: “The control of


Timings are important - water lilies, for example, should be sprayed from mid-July to mid-August


trees and cut tree stumps on watercourse banks has always been a problem, as previously approved products for such purposes, such as triclopyr or picloram, are not approved for use in or near water. Developments to Ecoplug Max now allow safe application of high concentrations of glyphosate to trees and tree stumps near water without the risk of spray drift.” It has a new formulation and is now authorised by the Chemicals Regulation Division, (CRD), ‘for use in all situations, (stump)’. This means that it can be used on land immediately adjacent to aquatic areas as well as stumps growing in water. Under an Extension of Authorisation for Minor Use in standing trees, the plug may now also be used where felling is not possible, by inserting plugs from the side of standing trees and leaving them in situ.


Plugs are used in a similar method


to stump control applications, but should be inserted from the side of the tree, evenly spaced around the trunk just above ground level.


Suitable targets


Ecoplug Max can now be used on land immediately adjacent to aquatic areas as well as stumps growing in water


As a general rule, plants are likely to be susceptible to glyphosate if they have a substantial part of their foliage exposed above the water surface. Plants are generally most susceptible when they have the maximum area of emerged leaf and around the time of flowering.


Emergent weeds


Agrostis stolonifera (Creeping Bent), Typha latifolia (Reed Mace, syn. Bulrush), Glyceria maxima (Reed sweet-grass), Phalaris arundinacea (Reed Canary-grass), phragmites australis (Common reed), Carex spp (Sedges), Juncus spp( Rushes), Rorippa nasturtium-aquaticum (Watercress), Rumex spp (Docks), Oenanthe crocata (Hemlock Water Dropwort), Fallopia japonica (Japanese Knotweed), Heracleum Mantegazzianum (Giant Hogweed), Impatiens Glandulifera (Himalayan Balsam), Solanum Dulcamara (Woody Nightshade).


Floating weeds


Aquatic areas are treasured landscape features on many golf courses and in parks, but weeds can cause problems for greenkeepers and groundsmen


144 I PC AUGUST/SEPTEMBER 2017


Lemna minor (Common Duckweed), Nymphaea Alba (White water lily), Nymphaea Lutea (Yellow water lily), Nymphoides peltata (Fringed water lily) and Potamogeton natans (Broad- leaved Pondweed).


Monsanto provides specific guidance


notes for other Lemna species; Hemlock Water Dropwort, Japanese Knotweed, Himalayan Balsam and Giant Hogweed.


Timing: Spray Watercress in June, Bulrush in late July, Water lilies from mid-July to mid-August and most other species from mid-August to mid-September.


Tricky customers


Recent changes in aquatic weed flora have resulted in many more aggressive alien invasive species becoming dominant, comments Dr Newman. “Whilst not very widespread, these species cause immense problems where they are present, and incur very large costs for management.” “Some of these species, including


Floating Pennywort (Hydrocotyle ranunculoides), Parrot’s Feather (Myriophyllum aquaticum) and Water Primrose (Ludwigia grandiflora) tend to be more resistant to glyphosate treatment because they either metabolise the herbicide very quickly, excrete it though their extensive root systems very quickly, or have waxy cuticles that prevent entry of the herbicide into the leaf.” “This problem can be overcome by the use of aquatic approved adjuvants, which sticks the herbicide to the leaf surface providing, in effect, a slow release formulation that allows sufficient herbicide to be taken up by the plant to provide a lethal dose.” The main factor in getting good


control of any aquatic or riparian weed is correct timing of the application, he points out, along with continuous monitoring of any that escaped treatment or have started regrowing after application. “Good selective weed control


allows other more favourable species to recover and become dominant. Generally, a weed control programme results in a more diverse plant flora, as the mono-specific dominant weed growth has been eliminated, opening up the habitat for less aggressive species.”


Weeds not well controlled by glyphosate


Glyphosate will not control submerged weeds or algae. These include the true pondweeds or Potomegeton, of which there are over twenty species, and the more common Elodea Canadensis (Canadian Pondweed) or Largarosiphon spp (Waterweed). Poor results can also be expected on Ranunculus aquatalis (Common Water Crowfoot), Hippuris vulgaris (Mare’s Tail) and Myriophyllum spp (Water Milfoil).


Best practice


Check with the Environment Agency, Natural England, Scottish EPA or Natural Resources Wales to establish if the proposed treatment area is under any environmental or European schemes which may need to give permission for herbicide application.


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