There are many ways to control plant pests and diseases.
The two main methods are biological and chemical methods. There are, however, substantial differences between these two.
Let’s take a closer look at the topic:
Chemical Pest Control
Chemical pesticides are often used to kill pests, diseases, or weeds. These products are based on substances that are toxic to the insects involved (and potentially, also to pets and humans).
For centuries people from all over the world have made efforts to protect crops, but it was only after World War 2 that the use of real chemicals began. Today, there are hundreds of chemical pesticides for agricultural and horticultural use.
Advantages and disadvantages of chemical pesticides:
Pesticides are divided into 5 main categories:
- Fungicides: These products act against fungi.
- Herbicides: are used against weeds. They are absorbed by the leaves or roots of the weeds, causing their death.
- Insecticides: pesticides that kill harmful insects.
- Acaricides or miticides: pesticides that kill mites and ticks.
- Nematocides: these products protect plants by killing harmful nematodes.
The use of chemical pesticides is widespread given the low cost, ease of use, effectiveness, availability, and (moderate) safety. Chemical pesticides are generally fast-acting, thus limiting damage to crops.
Unfortunately, chemical pesticides have some major drawbacks.
First of all, chemical pesticides are often toxic not only to the organisms for which they are used but also to other organisms such as beneficial insects, pets, or even humans.
Chemical pesticides must be distinguished into two groups:
- Non-selective pesticide
- Selective pesticides.
Non-selective products are the most harmful, as they kill all types of organisms indiscriminately, including harmless and beneficial species.
Selective pesticides have a more limited range: they only eliminate the pests or diseases for which they were specifically produced.
Often, a combination of different products is required to eliminate various parasites since almost all permitted products are selective and therefore only control a limited range of parasites.
Another drawback of chemical pesticides is resistance.
Pesticides are often effective on a particular organism only for a short period. These organisms can become immune to a certain substance, which therefore will no longer have the desired effect. When these organisms become resistant, other pesticides must be used to eliminate them.
The third drawback is accumulation. If the plant on which the pesticide is applied is eaten by one organism which in turn is eaten by another organism, the chemicals enter the food chain. Animals that are at the top of the food chain, usually predators or humans, have a greater chance of being poisoned due to the accumulation of pesticides in their system.
Finally, the last but most significant danger is residual substances of pesticides in crops. Residues can be consumed on fruit and vegetables, and for this reason, pesticides should not be applied to crops close to harvest.
What is Biological Pest control (also known as Biocontrol)
Biological control or biocontrol is a method of controlling pests and diseases using other organisms.
Biocontrol can be done following these three methods:
1. By using predators and parasitoids
2. By using micro-organisms
3. By using biochemicals
Let’s take a closer look at their meaning:
Biological control by using predators and parasitoids
Since ancient times, man has discovered that he could use a living organism to kill a pest.
These pest killers can be divided into two groups: predators and parasitoids.
Parasitoids are organisms that live at the expense of another organism, such as parasitic wasp larvae, which live in the larva of whiteflies and eat them from the inside.
Another example of parasitoids are beneficial nematodes.
These microscopic insects are used to control soil pests. They are not dangerous to humans and pets, as they only attack soil-dwelling insects leaving plants and earthworms alone. The beneficial nematodes enter the host via mouth, anus, or respiratory openings and start to feed on it. They produce a specific bacteria from their intestinal tract that spreads very rapidly and leads to host death.
Beneficial nematodes are sold alive. In this article you can learn more about these incredible insects and when it is the best time to apply them.
Predators are organisms that simply hunt other organisms for food, for example, ladybugs that feed on aphids. If you want to learn more on the subject, read this article about beneficial insects.
Biological control by using micro-organisms (microbes)
In nature, there are some micro-organisms that perform useful activities and that can be used to improve plant health and to control pests and diseases. These are bacteria and fungi that can produce antibiotics or simply feed on other harmful micro-organisms. Microbes can also be used preventively as they are capable of making plants stronger and healthier making them less exposed to the attack of pests and diseases.
Biological control by using resources of natural origin and pheromones (biochemical substances)
In addition to macro-organisms and micro-organisms, there are resources of natural origin and pheromones that can also be used to control parasites and diseases. This is a very broad category, which also includes plant extracts, vitamins, and plant hormones that act preventively to make plants healthy and strong.
Pheromones are used to lure parasites (insects) into a trap. Sex pheromones and aggregation pheromones are the most commonly used. Here is an example of pheromones used to attract moths (moth traps), mostly for indoor use.
The advantages and disadvantages of biological control
Biological control, like chemical control, has its pros and cons.
The first advantage is of course the use of natural resources that are not toxic to the environment or to humans.
The risk of pest resistance is also much lower since the parasites cannot develop resistance to the action of being eaten.
Natural pest control has a specific goal and is therefore an effective way to control particular parasites.
The disadvantages of biological control are due to the fact that natural enemies can move away. In greenhouses, this problem can be managed, while it is very hard to manage it in open spaces. It also takes time to apply to a larger area.
Secondly, parasites are never completely eliminated since the natural enemy needs to stay alive and therefore they will never destroy the entire population.
Last, but not least, before you can use any type of pest control, the parasite has to manifest itself, this means that the crops will suffer some damage before you can intervene.
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