The use of physical control methods alone often gives poor results. Physical removal of blackberry top growth will result in the death of only the crown, even when the regrowth is repeatedly removed for three to five years.
Blackberry can produce root suckers from a depth of at least 45 centimetres, so it is important to remove as much of the root system as possible when using these methods. Regrowth from crowns, root fragments and seed is inevitable, making follow-up control and site rehabilitation essential. Combining a range of physical control methods with the strategic use of herbicides is a more reliable approach.
Hand removal (removing the top growth of the blackberry and digging up the roots) is most suitable for small and isolated infestations. Blackberry can produce root suckers from a depth of at least 45 centimetres, so it is essential to remove as much of the root system as possible.
Mechanical grubbing is a good compromise that is suitable for scattered infestations of mature plants. With this method, whole blackberry plants are removed by an implement attached to a tractor, backhoe or excavator.
Scalping to a depth of 20 – 30 centimetres with a root rake or similar equipment can be very successful on accessible infestations. Care must be taken to remove sufficient material to ensure that the crowns and the majority of the roots are removed.
Cultivation is the process of digging up or cutting the soil to prepare a seed bed, control weeds, aerate the soil, or work organic matter, crop residues, or fertilisers into the soil. A single cultivation can spread blackberry rather than help control it, because root fragments are distributed over the cultivated area. This is usually the case if the cultivation is done in winter. Cultivation needs to be frequent and undertaken at the appropriate time of the year (usually summer) to achieve good control.
Large earthmoving equipment
Using large earthmoving equipment may be an option in specific situations. However, it is unlikely that all root material will be removed, and follow-up treatment with herbicides will be required to achieve control. Large earthmoving equipment can be used to cut access tracks into large, dense infestations. Other management options such as the use of herbicides or grazing by goats can then be used successfully.
Slashing should be considered only as a short-term control method. It may be useful in accessible areas to reduce plants to a more manageable size or to open up dense infestations for follow-up treatment using other techniques.
Regular slashing on a fortnightly or monthly basis encourages the blackberry to regrow and use energy reserves stored in the root system. This in turn may reduce the size and vigour of the infestation. However, it is very expensive and not very effective. Irregular slashing can leave the plant with a stronger root system and little top growth, reducing the effectiveness of any follow-up herbicide application. It may also stimulate suckering, which increases the density of the blackberry plants.