The Department of Conservation has released two papers on herbicide application and more details on the TDPA mix and its application for distribution through the Wilding Conifer Management website.

The papers provide important information on how to apply herbicides. The "pine control system" briefing paper deals with dense infestations (boom spraying), accessible scattered individual trees (basal bark technique) and inaccessible scattered indiidual trees (aerial bark application or ABA). To view the paper click here.

The best practice guideline deals with the ground-based and aerial bark basal applications. To view the guideline click here

Department of Conservation also provided the "TDPA" recipe for boom spraying of conifer infestations with a canopy cover greater than 80% (dense, closed stands). So far the mixture has had a greater than 90% kill rates based on trials carried out by DoC on a number of pine species.The TDPA mixture is as follows according to Pete Raal (DoC):

 

20 litres Grazon

20 litres Tordon Brushkiller XT

4 litres T-Max

10 litres Dicamba 500SL

20 litres Hasten spray oil

0.5 litres Companion

4 kg Kondemn

 

Note: Companion to be added to water before Dicamba is added.

18000g Triclopyr Ester

2000g Picloram

280g Aminopyralid

5000g Dicamba

20000ml oil

500ml Proprionic acid buffer

4000g ammonium sulphate

Note: apply at 400 liters per hectare for trees up to 10m tall and 600 liters per hectare for trees taller than 10m

The order of mixing the herbicides is:
1. Put in about 200 litres of water
2. Add the Grazon
3. Add the Tordon Brushkiller XT
4. Add the Companion (this is important because it buffers the water for the Dicamba!!)
5. Add the Dicamba
6. Add the Kwickin oil
7. Add the Kondemn (which has to be weighed out using a scale)
8. Make up the shortfall up to a total volume of 400 litres.

It is best if you can pre-mix the herbicides before putting it into the helicopter but, provided you have a good agitator in the machine, putting it directly into the helicopter tanks also works.

The cost is about $2000 per hectare plus GST including the helicopter costs.

Helicopter specifications
1. Because total wetting of all the foliage is required, the liquid herbicide mixture is to be boom sprayed as a medium droplet size (350 microns) spray at 400 litres per hectare as overlapping passes. This will ensure good foliar coverage.
2. In order to limit the spray released into the rotor vortices and significantly reduce drift spray booms should not exceed 80 percent of the rotor length.
3. The herbicide should be discharged at a height of 3 – 4 m above the canopy if possible.