What are pesticides?
What are pesticides?
As their name suggests, pesticides (or crop protection products) are treatments used to keep crops healthy. These chemicals either occur naturally or are man-made (synthetic). They help control diseases, insects and weeds that harm or destroy our food crops. Collectively, they are also known as pesticides.
When attacked by disease or pests, a plant’s natural response is to produce its own protection, in much the same way as humans produce antibodies. Man-made crop protection chemicals act as ‘medicines for plants’, only needed when the plant’s own defence mechanisms do not work well enough.
What is a pest?
Crops need to be protected from a variety of different pests, organisms that present a threat to the crop. While we often think of pests as insects, a pest can also be a weed, a disease or an animal (such as a rat) or even bacteria.
Targeting specific pests
Insecticides, fungicides and herbicides are all crop protection products. Insecticides are used to control insect pests such as aphids or greenfly. Fungicides deal with the fungi or moulds that can affect seed germination, crop growth and the quality of the harvested produce. Weed-killers control plant pests such as chickweed, cleavers and blackgrass that rob the crop plant of light, water and food.
While these three are the most common crop protection products, other types are used against specific pests. For example, molluscicides against slugs, acaricides for mites and rodenticides to control rats.
Pests can develop a resistance to the crop protection products. Resistance may be defined as a heritable change in the sensitivity of a pest population that is reflected in the repeated failure of a product to achieve the expected level of control when used according to the label recommendation. Cross-resistance occurs when resistance to one product confers resistance to another product, even where the pest has not been exposed to the latter product. Resistance may occur due to a repeated use of the same product, or use of products with a single mode of action in the targeted pest. The best approach to resistance management is Integrated Pest Management (IPM [linkto IPM]) which is the use of all available control methods in an economic and sustainable manner.
Finding the right balance
Insects, slugs and other pests, however, play an important role in the natural ecosystem. So 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.
By their very nature, these products have to be toxic – but only against the targets at which they are aimed. These days, 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.
