Eradication and control of Kikuyu

First of all, for those who do not wish to eradicate their kikuyu but also want to continue cropping. Trials have been done with sub lethal chemical rates by DAFWA. Crops have been grown successfully over kikuyu swards. Lupins, peas, canola and oats have all been grown and harvested whilst minimising any risk of soil erosion and still allowing the kikuyu to regenerate ready for summer grazing.

Kikuyu is a wonderful plant, unless it has been established in the wrong position, or your needs for that area change. Control is possible but eradication is more difficult. There are a few things that will help in understanding why it cannot be achieved in one year.

Firstly, kikuyu has an underground network of runners called rhizomes and for these to be killed the application of glyphosate needs to be applied while the plant is actively growing. This will allow the herbicide to be translocated through to the growing points. It is of little effect if the glyphosate is applied after a frost or in mid-winter when the plant is in a dormant state. The best time is in the early autumn or spring after a rain event.  An application of Nitrogen will also stimulate the growth and help with the movement of the herbicide.

Most kikuyu plants set seed, apart from the one sterile variety. The seed can be hard seeded so germination takes place over a number of months with associated rainfall events. With this trait the removal of kikuyu will require more than one application of Glyphosate. To help with the control I have seen a residual ground herbicide Propyzamide 500g/kg, trade name Edge, kill seedling kikuyu. It appears to have no effect if applied once the plant has developed stolons (above ground runners). This chemical can be a useful tool. However, it is a residual grass herbicide so you will need to think about your crop following the application. Canola followed by lupins with an application of a grass selective is also going to slow the recruitment. You will need to eliminate the seed bank in the soil to stop the regeneration.

The kikuyu seed can pass through the digestive system of animals so will carry seed from one location to another. To help prevent this transport of seed, livestock should be yarded or allowed to empty out in a feedlot where the food source will help push through any remaining seed. Fence lines left unsprayed or areas tight to access with machinery will provide a seed source for the grazing animal so will need to be controlled with a hand sprayer.

Tree lines planted before or at the same time as kikuyu planting will help to control the spread of kikuyu. It prefers not to be shaded out and pine trees in particular work well in this regard.  At this time, Rottnest Island Pine seems to be the most beneficial in terms of control. Tree Lucerne on the other hand, being a legume will encourage the kikuyu growth beneath it.