General

• Map infestations in mid winter - the bright flowers are highly visible.
• Decide where resources should be best spent - control isolated clumps in healthy bushland first.
• Spray just on flowering, at time of maximum bulb exhaustion but before bulbils begin to develop. Spraying after flowering will not kill the bulbs so there is no point.
• If hand grubbing, sift the soil to get as many bulbils as possible (only recommended for small populations in very disturbed areas or soil dumps)
• Removal and careful disposal of all plant material is important - bulbils and pieces of rhizome can spread the weed! (it is important not to waste effort by removing plants ineffectively).
• Follow up control in following years - map each year to check progress of control efforts and/or spread.

  NOTE: Cleaning mud, containing bulbils from tools, boots and vehicles is important in restricting spread.

As with all weeds it is important to control isolated patches within intact bushland before they spread. Work from intact bushland out towards the disturbed areas, This limits spread - especially where the infestation cannot be removed in one concentrated effort.

Physical Control

Grubbing of plants is only practical for small infestations in very disturbed areas or on soil dumps. Dig out the whole plant early in the season before bulbil formation, sifting soil to remove as many of the bulbs as possible. Due to the numerous small bulbils, this can be a very tedious task. Plant material should be taken from the site and disposed of carefully. Leave bulbs and plant material to rot in plastic bags placed in the sun. Soil disturbance resulting from the grubbing of plants will encourage other weeds to colonise the area and may spread the Oxalis species.

Chemical control

Timing of chemical application is crucial. Spot spray infestations just prior to flowering - this is the point of maximum old bulb exhaustion, and minimum new bulb development. Bulbs are empty, plants are committed to flowering and the majority of leaves have emerged. Time of flowering will vary from year to year and between sites. As not all plants will be at the same stage, further control will be required in the following years. Oxalis species are easily stressed by dry spells which reduces the effectiveness of systemic herbicides.

Take care to avoid off-target damage when using herbicides in bushland. It is important that training in the correct use of herbicides is undertaken. Always read the label and follow instructions.

The following herbicide reccomendations are made by the Western Australian Department of Agriculture fo Oxalis pes-caprae.

• Herbicide - metsulfuron methyl (minor use registration)
• Active ingredient - 600 g/kg metsulfuron methyl
• Rates of dilution for spot spraying - 1g in 100L
• Knapsack amount per 10L of water - 0.1g
• Rate of product per hectare - 5g
• Wetting agent dilution - 1:400
• Time of application - Winter, just on flowering

Additional information (EWAN)

Careful application of metsulfuron at these rates results in minimal off target damage. However the herbicde is soil residual (from 2 months to 2 years in dry calcereous soils) and may damage sensitive plants

At present there are no herbicides registered for use in Western Australia on Oxalis glabra or Oxalis purpurea in bushland. A permit is required for off label use of herbicides except where state 'control of use' laws are in place. A minor off-label-use permit (No. PER4984) covers the control of some environmental weeds in non-crop areas in WA. Herbicide application must comply with all conditions of the permit. A copy of the permit may be obtained from EWAN or the Western Australian Department of Agriculture.