Security Classification - None
Charles Fergusson Building, 34-38 Bowen Street Wellington 6140, New Zealand biosecurity.govt.nz
Milana Blakemore
Team Leader, Hazardous Substances Reassessments Environmental Protection Authority
Private Bag 63002 Wellington 6140
Milana.Blakemore@epa.govt.nz
23 August 2019 Dear Milana
Reassessment of paraquat-containing substances: biosecurity use
I refer to your letter of 16 August 2019 seeking further information on the use of paraquat-
containing substances for biosecurity use. The questions posed and their answers are addressed below.
1. Is paraquat named for use in any of Biosecurity New Zealand's management plans for generic or specific incursion response situations? If so can you provide information on the nature of the plan or species to be controlled?
Yes. Black-grass (Alopecurus myosuroides) is currently being managed in a response; through management during this response it is now known at only one site. During the autumn of 2019, black-grass was detected multiple times in an area of approximately 0.06 ha and a management plan conducted using a monthly treatment regime, alternating between glyphosate and paraquat, has been advised by the Foundation for Arable Research.
2. We are proposing to restrict paraquat to a maximum application rate of 600 g ai/ha per application, with an annual maximum application rate to 600 g ai/ha, for all application types including aerial, ground-based boom, and handheld uses. This is to give end-users some flexibility in multiple applications, i.e., we propose that an end-user may apply 100 g ai/ha six times in a year, or 200 g ai/ha three times per year, or any combination so long that the 600 g ai/ha per year is not exceeded. Please advise whether existing biosecurity operations would be effective under these restrictions with reference to both the proposed allowable application frequency and maximum application rate.
This would offer flexibility in application, but not quantity of a.i. – this will limit paraquat as a tool:
standard label rates for application are generally from 600g ai/ha per application, for the control of grasses.
3. The proposed application restrictions above require buffer zones of up to 100 m to protect non- target plants, and up to 15 m to protect water bodies for aerial application, and 5 m buffer zones to protect both non-target plants and water bodies from ground-based application. We are not proposing to implement buffer zones for non-motorised handheld equipment. Please advise whether existing biosecurity operations would be able to accommodate these buffer zones.
2
Aerial buffer zones have not taken into account the method of application – fixed wing will require a larger buffer zone than helicopter application. Also there needs to be consideration for the use of RPASs (drones) – this would be aerial application, but can be as targeted as spot spraying by hand.
4. If biosecurity operations would be ineffective under the restrictions proposed above, please advise what conditions biosecurity operations would require for the effective use of paraquat.
The most limiting factor above is the maximum application rates per year. The black-grass
response is the only response I am aware of that has had paraquat recommended to date (this to reduce risk of resistance and taking in account paraquat is more effective against grasses than diquat) but is for application over an area of 0.06 ha only. One option to reduce impacts on this response would be less restrictive limits for annual a.i. application for sites under a certain size (for example, less than one ha).
I trust that this letter answers your questions. Any future correspondence on this matter should be directed to Tim Ryder (Tim.Ryder@mpi.govt.nz) in the first instance.
Yours sincerely
Fleur Matthews
Team Manager, Long term Programmes
