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Aerial Spraying Workshop for Forest Managers

Aerial Spraying Workshop for Forest Managers

Every year PF Olsen staff manage and carry out aerial spraying operations across many thousands of hectares of land.  Aerial spraying operations cover both forested land (releasing of newly planted areas; Dothistroma control / other sprays for forest health) and bare land in preparation of planting (weed control).  From a forestry perspective, aerial spraying operations are one of the more potentially risky operations undertaken, until a forest is harvested.  Because of the nature of the operation, there is the potential for large areas of damage to occur, both of the crop trees and other areas (wetlands, riparian zones, neighbouring properties etc), from spilled chemicals, spray drift, and incorrect chemicals being used.  While spraying contractors (typically helicopter companies) are brought in to carry out the actual work, our staff are expected to have enough understanding of the risks, processes and chemicals involved in the operation to ensure that the work is carried out to the highest standards, and in compliance with all legislation.

To aid our staff in their work

PF Olsen organised an aerial spraying workshop for them in Christchurch in March. The two day workshop covered a range of topics by both in-house and guest speakers, including:

  • PF Olsen systems and processes;
  • What causes changes to the recommended chemical rates (weather, soil type, duration until planting, species to be targets, and species to be planted);
  • Buffer zones versus exclusion zones (buffers are areas of protection where some spray drift is expected to occur. Exclusion zones are areas where no spray or spray drift is tolerated);
  • Spray drift modelling; and
  • Using a drone for spray work.

Brian Richardson from Scion and Warrick Funnell from Agdrone Ltd presented via Zoom on spray modelling and using drones for spraying respectively. Both presentations were well received by staff, containing as they did several pieces of key information. Prior to the workshop Brian had carried out a range of spray modelling at Olsen’s request to determine how far spray would drift, and thus how large our buffer zones would need to be, under a range of scenarios. Variables including temperature, wind speed, slope of the land and nozzle size were changed across the scenarios to produce spray buffer guidance tables. Unsurprisingly, smaller nozzles produce smaller droplets which can travel further. The surprise was in how much further, with buffers of 300 meter plus suggested in some cases for the ultra fine nozzles (such as are used for Dothistroma control spraying), compared to ultra course nozzles which might only need a 5 m buffer for the same scenario.

Likewise, Warrick’s presentation on using drones for spray operations also gave many of our staff pause for thought. According to Warrick, his drones are capable of carrying up to 45 kg of payload, which is the equivalent of just over two knapsacks of spray mixture. With the ability to provide more targeted spraying, and a reduced risk of spray drift due to a reduced release height, it is likely that we will see an increase in the amount of drone spraying in the future to quickly, easily and safely spray around sensitive areas.

Finally, the workshop wrapped up with four desktop exercises and a field trip. Spraying scenarios, based on recent spraying operations were provided to the staff to work through in small groups. Each group was provided with maps of the area to be sprayed, relevant council rules, weather conditions, and site information (weeds present, site access, neighbors etc). They then had to come up with cunning plans for how they would spray the block (aerial vs drone vs knapsack), noting water sources, sensitive areas, buffer zones and exclusion zones. Once each group had presented their plan, the staff member in charge of the operation then presented on how they actually sprayed the block, along with any challenges they encountered whilst spraying, and key learnings from each operation.

A field trip out to Waiaki Forest allowed staff to put all of the learnings from the workshop into practice, by reminding them that while desktop assessments are a good starting point, pre-operation block inspections also yield a wealth on information that aid the planning of any spraying operations.

A great two days with excellent collaboration by staff and speakers!

PF Olsen would like to thank Andrew Pattullo from AGPRO, Brian Richardson from Scion, and Warrick Funnell from Agdrone Ltd for giving up their time and presenting to our staff.