Use of pesticides declines as organic farming grows

WELLINGTON - A total of 3300 tonnes of chemicals was used in herbicides, pesticides and fungicides in New Zealand last year.

The pesticide use - other than mineral oils usually sprayed on fruit trees - was lower than the peak of 3700 tonnes a year between 1984 and 1994, according to a report from the Ministry of Agriculture and Forestry.

Commissioned in April, it canvassed pesticide use in New Zealand, based on research by Dr Pat Holland, of HortResearch, and Dr Anis Rahman, of AgResearch.

They said herbicides continued to dominate pesticide use (68 per cent), followed by fungicides (24 per cent) and insecticides (8 per cent).

Rapid increases in organic production in all agricultural sectors would have an effect on pesticide use in future.

About two-thirds of present total use was concentrated in four classes of pesticides (phenoxy hormones, phosphonyls, inorganic fungicides and dithiocarbonates), which "have excellent records of very low human and environmental risks" when used correctly.

Changes in use of the main pesticides classes in the past decade showed significant declines in some hormone herbicides, organophosphorus insecticides and dicarboximide fungicides, while phosphonyl herbicides (mainly glyphosate), triazine herbicides, sulfonylurea herbicides and pyrethroid insecticides all increased.

These changes apparently reflected trends in land use (more forestry) and cost-effectiveness (more glyphosate and sulfonylureas).

Adoption of integrated pest management with more use of biological pest controls, and less use of organophosphates and dicarboximides, also had an effect.

Pesticide use in pastoral agriculture was static or declining, and was largely herbicides for broadleaf and brush weed control.

Cereals and other arable crops also mainly used herbicides, with resistant cultivars and integrated pest management techniques contributing to reduced insecticide and fungicide inputs.

But apple crops still had relatively high use of pesticides, despite increased adoption of integrated fruit production strategies.

Pesticide use in process vegetables such as asparagus, green peas and sweetcorn was "relatively low" and mainly concentrated on early season weed control.

In contrast, fresh vegetables such as lettuce, brassicas and potatoes tended to have intensive spray programmes throughout their growing seasons.

Pesticide use in plantation forestry was concentrated on weed control during the first one to two years, with minimal use in the rest of the timber-production cycle.

For agriculture and forestry as a whole, weed control was often the main priority, and herbicides still the most cost-effective technology.

- NZPA