What is a Pest?
A pest is any organism that is causing plants to produce less than they otherwise would. When organisms are part of a natural ecosystem, or are beneficial to people, then they are not pests. There are many different kinds of pests.
The Pest Problem
In natural systems, organisms have parasites, predators, or competing plants that help to keep their numbers in check.
Pests which cause the most problems are:
Insects (are consumers, because they eat some or all of the plant)
Fungi (cause infections which can destroy all or part of the plant)
Weeds (Common Weeds) (are thieves, because they steal moisture, nutrients, light and space from the plant crop)
Dandelion: Profile of a Champion Competitor
Dandelions are successful weed pests because they have:
- Powerful roots (long taproot)
- Broad Leaves (shade other plants close by)
- Super seeds (easily carried by the wind)
? And they are very adaptable, because they grow well in any kind of soil and often survive because they are hardy and can easily be missed by the lawn mower (because of their short flower stalks).
(See profile on p. 165)
Canola and its Pests (Ref. 'WANTED' p. 166) Invasive Plants of Canada
Bertha Army Worm
Cinchbugs (insect species bios)
Each food and fibre crop has its own unique set of pest weeds, insects and fungi. Sometimes exotic pests are introduced from other countries by accidental exposure to the crop (or sometimes intended). These types of pests can often become serious problems, because they may not have any natural predators, or environmental controls.
Quack grass, thistles and chickweed are examples of some exotic weed pests.
Dandelions were introduced to North America, from Europe, to be used as a salad vegetable. Naturals controls were not present and , as a result, dandelions thrived and over populated the country (coast to coast).
The European bark-boring beetle was introduced fro the Netherlands in a shipment of logs. Unfortunately, it also brought with it a fungus, called Dutch Elm Disease, that has almost entirely wiped out the native elm trees of North America.
There are various ways that pests can be controlled:
Large pests can be chased, or scared away
Smaller pests can be picked off the crop by hand
Machines (like cultivators and ploughs) can be used to uproot pesky weeds
Different crops are grown each year (crop rotation)
Regular summer fallow (controlled pests, but led to soil damage)
Chemical controls (herbicides, insecticides and fungicides)
Concerns with Chemical Controls
Long term problems were created with the extensive use of pesticides.
Bioaccumulation - Pollutants move from level to level in the food chain. Bioaccumulation is a primary concern with the use of chemical pesticides, because as the chemicals move from level to level they accumulate in the organism. Organisms at the top of the food chain are the most adversely affected.
Soil Residue - Some of the chemicals used as pesticides wash off the plants and leave residue in the soil and water. If the chemical is not easily decomposed they remain in the soil and can be poisonous.
Harming Non-Target Organisms - Pesticides are often be toxic to organisms they were never intended to harm (like earthworms who can be exposed to pesticides from soil residue and ladybird beetles who eat aphids can be killed by the pesticide used to control the aphids)
Resistant Species - As pesticide use increases, pests can (over time) develop a resistance to the toxic effects of the chemicals being used.
Alternatives to Pesticides
Organic Food Production
Organic food is food that has been grown without the use of chemical fertilizers and chemical pesticides. Manure and compost is used to add nutrients to the soil. Pests are controlled by crop rotation, tilling, mulching, companion planting and removal of insects by hand.
Other techniques used to discourage the need for chemicals are
using good quality seeds
removing weeds before their seeds mature
cutting weeds along property lines
cleaning equipment to reduce transfer
planting a variety of crops (instead of monocultures) - increasing diversity
Organic Farming can be more expensive, but the quality is much better, the environment is less harmed and there is a higher level of safety fro the farmer (without using chemicals)
Using a pest's natural predators (enemies) to keep it's numbers under control is an effective technique, provided the species used to control the pest has its own predators to control its numbers.
Producers and Consumers - Partners in Sustainability
Producers, such as farmers and foresters must make very careful economically feasible decisions about what to produce and the practices they use to produce it. Consumers must be more conscious of interdependence, and environmental impact factors, which must be taken into account, besides the cost, to ensure that the food and fibre industry is sustainable.
Topic 6 Review p. 174
Wrap-Up (Topics 4-6) p. 175
Unit Review pgs. 180 - 183