Pests are damaging because they attack and eat vegetables and other crops, cause and spread disease, or damage stored food. They include weeds, insects, pathogens and animals such as rats.

Crops need to be protected from the wide variety of different pests and organisms that present a threat.

Pests typically reproduce very quickly so their population can increase rapidly, leading to infestations which destroy entire crops.

Controlling pests

Naturally occurring compounds or natural extracts have been used as pesticides since ancient times.

The earliest pesticides were most likely salt, sulfurous rock, and extracts of tobacco and red pepper. The insecticidal qualities of chrysanthemums, which produce pyrethrum, were known 2000 years ago.

Many other species have developed their own ways to combat pests though the action of their own self-produced chemicals.

Pesticides

Pesticides control pests in agriculture and horticulture. Insecticides, fungicides and herbicides are the three most common types of pesticides for protecting crops.

Herbicides control the weeds which compete with the crop, robbing it of light, water, and food.

Insecticides are used to control insect pests such as aphids and flies, which consume crops or burrow in to fruit to lay eggs.

Fungicides deal with the fungi or moulds that can affect seed germination, crop growth and the quality of the harvested produce.

While these three are the most common crop protection products, other types are used against specific pests. For example, molluscicides against slugs, miticides for mites and vermicides to control worms.

Striking a balance

Insects, slugs and other pests play an important role in the natural ecosystem. It’s important to strike a sensible balance between healthy, profitable crops and the wildlife that thrives in and around the area.

Pesticides can be applied:

  • to fields or seeds before planting - to protect the growing crop
  • to harvested produce – to prevent deterioration in storage
  • during processing, packing and transport – to protect the food’s quality, appearance and shelf life.

Modern crop protection products are specifically designed to have three characteristics.

They must be:

  • Safe – not harmful to people that come into contact with them during their manufacture, application or at the point of consuming the food.
  • Specific – only effective against the diseases, insects and weeds at which they are aimed.
  • Short-lived – after having the desired effect, they should break down easily into simple, harmless chemical components, without harmful impact on the environment.

Use of glyphosate in New Zealand

Glyphosate has over four decades of use in effective weed control.

Approximately 25 companies in New Zealand have registered glyphosate-based products.

Regulatory and scientific authorities worldwide, including New Zealand and Australia, have concluded that glyphosate, when used according to label directions, does not pose an unreasonable risk to human health, the environment, or pets.

Factsheet: Glyphosate use in New Zealand