PasturesThe concept of biological control of insect pests was brought to the forefront after the banning of the use of DDT as a pesticide for pastures which in New Zealand began in 1964 and then a total ban for all uses in 1989. The dangers of DDT were highlighted by a popular book: ‘Silent Spring” written by Rachel Carson in 1962.

The book brought unprecedented worldwide attention to the environmental damage of chemical pesticides, particularly DDT which was commonly used for a variety of insect pests.

During this time (1967) I was completing a PhD study at the University of British Columbia on an insect virus isolated from the larvae of Tipula spp. commonly referred to as leatherjackets. This insect had established itself as a pest in dairy pastures in the lower Fraser valley near Vancouver. The virus was called Tipula iridescent virus (TIV) and it was thought that introduction of this virus might control the pest population. The virus had been previously isolated by the Oxford Forestry Institute group in Oxford, England.

My studies revolved around the biophysical and chemical properties of the virus and I never had the time to explore the possible use of it in controlling insect populations. This group of insect viruses (Iridovirdae) have continued to be studied elsewhere and have been shown to have some unique evolutionary and biochemical features.

About the time that I moved to New Zealand (1969), carrying a copy of Rachel Carson’s Silent Spring, the use of DDT was being banned for use in pastures. As a consequence a large number of pastures were being severely damaged by the two insect pests commonly referred to as porina and grass grub. My arrival was somewhat serendipitous since a biological control research project had already been initiated in the Microbiology Department. I took over the programme and after 20 years and several PhD’s we came to some understanding of the molecular biology and the ecological role viruses play in pest population control.

The short story is that naturally occurring viruses are able to control the insect pests and provided that a small number of insects (below an economic threshold) are present they are able to maintain a virus reservoir sufficient to prevent any population escape. Certain pasture management practices were recommended in order to maintain an ecological balance and to ensure the ‘clean – green’ image of NZ pastures.

One of the key aspects of this research was sharing the knowledge with the farming community by attending their meetings and conferences and making presentations and displays and handing out information and publishing in their journals. Also it was important to get the message across that a small number of insects was okay (we monitored these to be sure that viruses were present).

For more see BioScience-1980-Kalmakoff