A farmer’s field is a complex environment. Many factors play a role in what is happening in the field. Often it is not possible to give general recommendations because a lot of management practices may have both a positive and a negative side.
For example: Mulch of rice straw is used to grow eggplants on an organic farm. We can recognize advantages and disadvantages of this practice:
- Some pest insects pupate under or between dead leaves that are laying on the ground. For this reason it may be useful to remove dead plant material from the field.
- However, as a mulch these plant parts can also be useful in maintaining the fertility and humidity of the ground. Mulch also provide shelter and a source of food for beneficial insects or spiders. This would be a reason for keeping the dead leaves in the field.
Therefore, it is up to the farmer to make observations in his/her field, to analyze his/her specific situation and to make an informed decision. This process is called “Agro-ecosystem Analysis” or AESA.
On this page we discuss in alphabetical order, a number of methods that could be used to manage the crop and to manage pests. The idea is not to give recipes for a specific problem, but rather to explain how each method can have an effect on the pest population and on the health of the crop.
Farmers and extension workers can use this knowledge to improve their cultivation methods. By experimenting in their own fields and by combining the appropriate methods they can develop their own system of Integrated Pest Management.
Click on each of the following IPM components for more detailed information:
Avoid resurgence
If broad-spectrum pesticides are used they will kill the natural enemies that normally keep pests under control. The pests can then multiply rapidly in the absence of these crop defenders. This is called resurgence.
Bacillus thuringiensis
Bt is biological insecticide, which is a very specific product to control caterpillars.
Bagging
Covering developing fruits with paper or plastic bags is a way to prevent pests attacking the fruits.
Baits
Bait consists of a mixture of a substance to attract the insects and an insecticide to kill them.
Biological control
Biological control is the use of natural enemies such as predators, parasites, and pathogenic micro-organisms or antagonists to control pests or diseases.
Botanical products
Many plants have insecticidal properties. Extracts of these plants can be sprayed on the crop to either kill or repel insects.
Chemical control
If other methods have failed, it may be considered to use synthetic pesticides to control pests. However, the use of these products involves risks and they can harm the environment.
Clean cultivation
During field visits, sick plants and infested leaves or branches should be removed and destroyed.
Clean planting material
Plant parts that are used for multiplication purposes should be free of diseases to avoid infecting the next crop.
Compost
Compost helps to improve the soil structure and fertility, which is needed to grow a healthy crop. The composting process also partly removes diseases, pests and weeds in crop residues, which could infest the crop in the following season.
Conserve defenders
Conserve and augment natural crop defenders by avoiding use of toxic chemicals and by creating optimal conditions for the development of beneficial insects.
Cultural control
With careful timing and a combination of agronomic practices farmers can make the environment less favorable for the increase of pests or diseases.
Defenders
Many beneficial insects and spiders and even pathogens are helping the farmer to defend the crop against pests.
Destroy crop residues
Plant residues that remain in the field after harvest often still contain pests or diseases. Destroy them to avoid infecting the next crop.
Destroy sick plants
Some diseases may spread rapidly through the field. Sick plants are a source of new infestations and should be removed and destroyed.
Distance between plants
The micro-climate in the crop can be manipulated by using optimal plant spacing.
Emergence boxes
Collected egg masses of pest insects can be placed in emergence boxes. These are constructed in such a way that the emerging parasites (adult wasps) can escape, while caterpillars remain trapped inside.
Fertilizer management
Use of the correct dosage and timing of fertilizer applications is a key to growing healthy crops.
Green manure
The use of green manure can help to improve soil fertility which is needed to grow healthy crops.
Hand collection
Hand collection can be used for controlling bigger insects that are easily visible. It involves a lot of labor and is thus more suitable for smaller fields of vegetables in homestead farming.
Inter-cropping
Outbreaks of pests and diseases are generally less serious in mixed cropping systems.
Inundation
If fields can be inundated, this can be used as a technique to control certain crop pests.
Irrigation
Proper water management (irrigation, drainage) is required to grow a healthy crop. Soils that are too dry or too wet will weaken the plants and make them vulnerable to pests.
Manure
Manure can be used to increase fertility of the soil and to improve soil structure. It provides nutrients to the plants and keeps the soil healthy.
Mulching
Covering the soil with organic matter can prevent evaporation of moisture, it reduces weed problems and it improves soil fertility. The mulch also provides shelter and food for beneficial insects.
Natural enemies
Natural enemies destroy pests and can usually maintain pest populations at a fairly low and steady level. This balance can be easily disrupted by pesticides that not only kill pests but also kill the natural enemies.
Neem
Extracts from the Neem tree, especially from the seeds, can be used as botanical insecticides or as repellents. They form a promising alternative for synthetic pesticides.
Net houses
Cages of fine netting can protect the crop from insects. They can be especially useful in nurseries.
Parasitoids
Parasitoids are natural enemies of pests. They help to keep pest populations at low levels. Farmers should conserve parasitoids and create conditions that favor their development.
Pathogens
Pathogens are parasitic micro-organisms that cause disease in their host. They can be fungi, bacteria or viruses that play a role in the biological control of pests.
Perching
Perching is a way of improving conditions for predators (insect eating birds, dragonflies) that feed on pest insects.
Pheromones
Pheromones are chemical odors that can be used to attract insects. They can be use for example as baits in traps.
Plowing
Plowing the field will kill weeds and it helps to loosen the soil. But it also controls certain pests by burying them or by exposing them to sunlight.
Predators
Predators, such as spiders, are natural enemies of many pest insects. Farmers should protect the predators as they will keep pest populations at a low level.
Ratoon crops
Ratoon give often poor yield, but they provide young leaves on which pests can feed and multiply. It is often recommended to avoid ratoon.
Resistant varieties
If a plant is resistant against a pest, it will not suffer any damage from that pest. By planting resistant varieties a farmer can avoid pest problems.
Rotation
Crop rotation is generally recommended to reduce the impact of pests and diseases and to manage soil health.
Seed selection
Good quality seeds are needed to grow a strong and healthy crop. Healthy seeds can be bought or farmers can produce their own seeds. Careful seed selection will improve the quality of seeds.
Seed treatment
Heat treatment or chemical seed treatment can be used to get healthier seeds and to avoid seed-borne diseases.
Simultaneous sowing
In some situations, simultaneous sowing can be used as a method to reduce the risk of certain pests.
Soap
Several pests, for example aphids, can be controlled by using simple soap solutions.
Soil cultivation
Populations of several pests that are present in the soil can be reduced by plowing.
Solarisation
The heat of the sun can be used to reduce pests and diseases in the soil. Solarisation can be useful in small plots and seedbeds.
Tobacco extracts
Extracts of tobacco can be used as insecticides. But care should be taken because of their toxicity and because they also kill beneficial insects.
Tolerant varieties
Some crop varieties are tolerant to pest attack. The pest can live on these plants, but without causing damage. Tolerant varieties are an elegant way to avoid crop losses by pests.
Traps
Different types of traps can be used to catch insects. Some traps are used only for monitoring insect populations, but some traps can also be used to for controlling pests.
Trichoderma
Trichoderma is an antagonistic fungus that can be used to kill plant pathogens or reduce their populations. It is commercially available in several countries including Thailand.
Trichogramma
Trichogramma species are very small wasps that parasitize mainly eggs of butterflies and moths. Avoiding pesticide use helps to conserve natural populations of these efficient natural enemies. Mass rearing and release of these wasps is another option to control certain pests.
Variety selection
In many crops, there are varieties that are resistant or tolerant for certain insects or diseases. The use of resistant varieties and tolerant varieties is an efficient and sustainable method to avoid crop losses by pests and diseases.
Viruses
Insects can be killed by certain viruses that occur naturally. Some of these viruses can be multiplied in the laboratory and formulated as a biological pesticides.
Water management
Proper water management (irrigation, drainage) is required to grow a healthy crop. Soils that are too dry or too wet will weaken the plants and make them vulnerable to pests.
Water spraying
Small insects can be controlled by just spraying water over the plants.
Weeding
Weed control is sometimes needed to remove unwanted plants that compete with the crop for space, water and nutrients. However, low populations of weeds can be tolerated and can even be beneficial for the crop ecosystem.
Wood ash
Dusting the plants with wood ash can be used on smaller plots of vegetables to control certain insect pest.
The above collection of IPM practices shows that farmers have many options to manage the health of their crops. Some of these methods can have both positive and negative effects. Experimenting with various options in his/her own field will help the farmer to further develop his/her knowledge and will result in better decision making.