THIS week’s weed of choice is Common Lantana (Lantana camara). The choice of adjuvants (wetting agents or surfactants) can have a great bearing on outcome with Lantana spraying as it can prove to be difficult to control.
Lantanas are category 3 restricted invasive plants so we are all required to control their spread but Lantana Camara is one weed I’m sure we all see more regularly than we should.
I suspect that a large part of the problem is that some organisations have simply given up on it and have come to accept its presence which is disappointing because it is very controllable.
The main problems with it are that it is very woody and it often has a low ratio of leaf to total biomass meaning that we have a limited area for herbicide absorption in comparison to area covered by the weed especially when under stress at certain times of the year.
For this reason, different herbicide labels will recommend a particular time of year for application, generally excluding the period from late May through to the end of September but this doesn’t mean you can’t take any action at this time of year.
Setting yourself up for a good Summer herbicide application when it is actively growing by running a slasher or plough through it the colder months will force it to burn up stored reserves in regrowth and lower that total biomass leaf ration when you come back to spray the new shorter growth.
You may require a second application to finish it off the following season but with a seed base already established it should be in your control plan to return to the site for the next four years regardless.
In small infestations or where we can’t get larger gear in we simply cut it back hard with a heavy duty hedger.
Often this cutting back can give access to a treatable stump that can be freshly cut and swabbed with a variety of herbicides like Garlon or Access diluted in diesel or my preference for ease of use Vigilante Gel but just as often Lantana’s habit of stems rooting where they contact the ground or the sheer number of stems makes this very time consuming and the return visit in later months for foliar application is a more viable method of control.                                                                                                          There are a range of herbicides that will do the job including Amine formulations of 24D and Hotshot if you don’t mind a seven day withholding period or a good quality Glyphosate if you can handle some off target damage.
But I have found a definite benefit can be gained by the addition of any of the many brands of herbicide containing Metsulfuron-Methyl @ 600g/kg as its only active ingredient in the mix. On its own it’s not the best on Lantana but in combination with other modes of action it’s fantastic.
If withholding periods are an issue and/or I need to limit off target damage my go to herbicide is Grazon Extra.
With any type of foliar application you need to put plenty on, spraying until its dripping off which is another reason why we want that smaller tighter leafed new growth plant to reduce the volume of herbicide use and definitely with this weed - use a good quality surfactant.