Blackberry (Rubus fruticosus agg.) - Getting to the root of the problem!!



History
The blackberry was introduced to Australia in the early 1830s, it now covers more than 8.8 million hectares.

There are 14 introduced species of blackberry, most are highly competitive and can quickly invade & dominate a vast range of different land types from improved pastures, natural ecosystems such as bushland & waterways, to roadsides and even urban areas.

The major impacts of blackberry include -

  • Displacement of native fauna resulting from the loss of natural habitats & biodiversity
  • Harbouring introduces pest species such as rabbits, foxes & deer.
  • Reduced stock carrying capacity of improved pastures
  • Restricting access to land & water causing tracks that result in increased erosion and waterway degredation

Getting to the root of the problem
Have your blackberries re-grown after spraying?

A significant proportion of the vegetative mass of a large blackberry bush is underground in the crown and root system. The root system is the only perennial part of the plant, (the canes are not perennial, but generaly bi-annual).

The crown can grow up to 20 centimetres in diameter and the main root can grow down to four metres.

Numerous secondary roots grow horizontally from the crown for 30 - 60 centimetres. These secondary roots then also grow down and further thin roots shoot in all directions. Large thickets will have many crowns.

The roots also have dormant rhizomes which will shoot only after the main root system has died, this is why re-growth is often seen 2 years after the initial spraying.
To prevent these rhizomes from growing to the surface, some selective but residual herbicide activity is required

Timing of herbicide application - Why is it important
In order to effectivily control Blackberries & minimize re-growth, it is critical that lethal quantities of herbicide are transported into the root system. For this to occur, the herbicide must move in the phloem with the plant sugars produced through photosynthesis.

In early summer during the rapid extension of canes and expansion of foliar tissue, carbohydrates are transported within the plant from the root system up to the shoots. After midsummer, the first-year canes (non-flowering shoots), are actively transporting carbohydrates back down to the root system to be stored for the following year's growth. In the flowering shoots (second-year canes), the movement of sugars to the root system occurs later in the season than it does for first-year canes and is most active after the plant has set fruit.

This is why it is very important to ensure that the herbicide application coincides with the maximum rate of carbohydrate movement to the root system.

The correct herbicide applied at the optimum time can greatly reduce the amount of regrowth in subsequent years

The control of large blackberry infestations is a long-term process and cannot be achieved with a one-off effort.
Developing a simple control plan that considers all management options is very usefull

 

Herbicides are highly effective tools for controlling blackberry, and their use is currently the most reliable method for achieving eradication.

 

Leaving desirable species to thrive by selective spraying is an important technique that helps to minimise re-invasion & enhances site re-habilitation