A contract with a major international brewery for pesticide-free hops could be the first of many as growers cash in on
New Zealand’s unique conditions and the results of more than 10 years of scientific research.
The hops were grown using predator insects instead of chemical sprays to control the only real pest of hops in NZ – the
two-spotted mite.
The predator monitoring programme has been more than 10 years in research and development and was used for the first
time last year to produce a commercial consignment of hops designed for export. Developed by the Hop Research Group at
HortResearch’s Nelson Research Centre, the programme opens up huge possibilities for NZ-grown crops as demand for
pesticide-free and organic crops increases.
Scientist Ron Beatson, who has developed the programme with technician Trish Virgin, said that hop growers in Europe and
the United States have no choice but to spray –usually between 10 to 20 times a season. They face fungal diseases and a
hop aphid that will devastate the crop if let untreated.
“We’re lucky here that the two-spotted mite is the only real pest,” he said. “Last year about eight growers tried using
the predator mite monitoring programme and this year it is being used on a wider basis across the growing industry.
“Costs are similar and growers are finding that the extra work involved in introducing the mites to the hop garden and
monitoring them is well worth the effort as overseas buyers will pay a premium for spray-free hops.”
Growers buy boxes containing 1000 predators on bean leaves. The leaves are attached to hop plants in the field and the
predators then build up and eat the two spotted mites.
Growers send leaves to HortResearch throughout the season so that researchers can check that the correct ratio between
mites and predators is maintained.
The next step in the programme is an attempt to gain Agmardt funding so the scheme can be better co-ordinated, with
training days for growers so that they learn to identify the mites and can carry out their own monitoring.
ENDS