Getting the drift of aerial spraying
When a group of scientists congregated in the middle of the desert in Utah, it was an unlikely setting for a trial that will ultimately benefit New Zealand biosecurity operations. This aerial spray trial arose from an international research collaboration to tackle the problem of how to apply sprays safely and efficiently.
Dr Brian Richardson of Ensis Forest Biosecurity and Protection says efficient aerial spraying can make an important contribution to New Zealand’s biosecurity defences. For this reason, aerial spray research is supported by the Better Border Biosecurity (B3) programme, Biosecurity New Zealand (BNZ) and the Forest Biosecurity Research Council.
"Aerial spraying has been used on a number of occasions in New Zealand to eradicate insect pests that pose a risk to our forest resources. The more we understand about spray application, the better we can ensure that these high profile and costly operations are conducted with maximum safety and efficiency," Brian explains.
Long range spray drift studied
In the recent Utah trial, aerial spray specialists from Ensis in New Zealand, the USDA Forest Service, the US Environmental Protection Agency and the Canadian Forest Service came together on a US army base to study the process of long range spray drift. Brian says this international collaboration came about because issues surrounding spray drift are shared throughout the world.
"This is one of the most challenging trials we’ve been involved in due to the scale of the operation, and the environmental conditions."
Researchers working in temperatures approaching 40° C set up a sampling grid to monitor spray drift and weather conditions. After each spray run, they had to collect samples by walking four kilometres across desert terrain too broken for vehicle access.
"It was thirsty work walking up to 20 kilometres each day for a week to process the samples, but it was worth it. Our results will provide important information that will help operational managers to ensure spray drift remains within acceptable levels," Brian says.
Significant role for NZ researchers
New Zealand researchers, Brian Richardson and Stefan Gous, have played a significant role in this international research effort since the late 1980s. They have contributed to a strong track record of science and innovation that has given rise to a number of spray modelling systems, culminating in the latest product called "Spray Advisor". This software can be used by operational planners to ensure aerial spraying is conducted safely and cost effectively.
"When planning an incursion response there is so much information required to make the best decisions, especially in the urban environment where public safety and accountability is paramount. These complex problems can be addressed with the sophisticated modelling tools that we have developed," Brian explains.
Dr Harold Thistle of the USDA Forest Service recently visited New Zealand to present the latest spray model developments to BNZ and the forest industry, both of which have helped to fund this work. Following a summary of Spray Advisor, a new modelling system, "Spray Trans", was introduced. Spray Trans is designed to predict the movement of spray over complex terrain (hills and valleys); the purpose of the Utah trial was to collect data to validate this new system.
Brian says the spray trials and model developments build on underpinning science to ensure future incursion response operations are more accurate and effective.
"When the time comes for our next incursion response, knowledge gained in the Utah desert will have relevance over a vastly more complex and heavily populated landscape. After all, the physics of spray drift are the same all over the world."
In recognition of the value of this research to New Zealand incursion responses, this work is partially funded by the Foundation for Research, Science and Technology through the Better Border Biosecurity (B3) Programme.
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Page last updated: 30 April 2008