Technical
Treatment with chemical thinning is one option - here one plant in a line has been treated
is almost immediate from a fresh cut and will be rainfast within ten minutes.
Application to a cut that has partially sealed means absorption is slow and rain within six hours will wash some of the product off.
Apply a 20% solution of Roundup Pro Biactive/ProBio or 16% Roundup ProBiactive450 in clean water using a knapsack sprayer, spot gun or paintbrush.
Alternatively, Ecoplug Max plugs can be used effectively, ensuring the risk of environmental or operator contamination is minimised. The plugs can be used all year round, in all weather conditions. For rates see table.
Chemical thinning
This method works from slightly earlier in the season, late summer, which may be useful to consider where stump painting in November is not convenient. It has the benefit of not requiring the stump to be freshly cut, so it can be used where they have already been cut back, or where the plant is to remain in situ. It is also easy to see which areas have been treated.
Neat Roundup is introduced straight into the phloem through a hatchet cut into the bark of the standing Rhododendron or stump. The cut can be made using a small axe - it is advisable to make a second cut under the first to catch any surplus herbicide. Alternatively a small hole can be drilled with an 8mm rechargeable drill at a slight angle towards the centre of the trunk.
A cut/hole with 2mls or
1.6mls dose is needed for each 10cm diameter of the trunk. Work out how many are needed and space them round the girth, e.g. a trunk of 30cm diameter requires three treatment points.
A spot gun with a solid stream nozzle is recommended to apply the Roundup. Application rate per hatchet cut/hole: 2mls of neat Roundup Pro Biactive/ProBio or 1.6mls Roundup ProBiactive 450 per 10 cm diameter of trunk.
Remember to plan to revisit the site and spray out any new seedlings. These will rapidly germinate after the removal of the canopy and following soil disturbance. A visit 2-3 years after the initial treatment would be appropriate to control both seedlings and re-growth.
Rhododendron facts
Rhododendron’s name is French, but originally derives from Greek, meaning ‘rose tree’. Rhododendron Ponticum is the state flower of Kashmir, while Rhododendron Maximum features in the State Flag of West Virginia, USA.
For more information visit the website:
www.monsanto-ag.co.uk or contact the Technical Helpline on (01954) 717575 or e-mail:
technical.helpline.uk@
monsanto.com
Coille Alba’s Donald Kennedy at work
OCTOBER/NOVEMBER 2013 PC 133
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