Integrated Pest (Disease & Weed) Management (IPM): Principles, Practices and Advantages

The problem of pest (and pathogens) resistance to pesticides

The release of pesticides has significantly helped the farmers protect their production and increase crop yields, keeping the crop pest population under control. However, the excessive and incautious use of these substances has led to great selection pressure on crop pests, leading to the rise of pesticide-resistant species. These species could be resistant to one or multiple modes of action and, as a result, to multiple pesticide products used for pest control. The development of new chemical modes of action by chemical and agricultural industries becomes more and more challenging, while in many cases, there are no available, suitable, and certified/approved pesticides for certain enemies.

At the same time, the use of non-selective pesticides and the lack of following essential guidelines for safe use have led to the decline of beneficial insects like pollinators and predatory insects, making the problem even bigger. Moreover, the risk to human health due to residues of pesticides found on products after the harvest due to non-compliance with the guidelines and safety measures is alarming.

Integrated Pest Management (IPM)

Integrated Pest Management (IPM) is a set of practices focusing on treating specific crop pests holistically. This strategy has been successfully applied worldwide in various crops, farm sizes, and environmental conditions. Based on Bajwa and Kogan, there are approximately 67 different definitions of IPM. It is a strategy of pest and disease management with a holistic approach combining different techniques of biological and chemical control, resistant varieties, cultural practices, and habitat manipulation. The goal is to have a long-term efficient management of crop “enemies,” minimizing the risk and negative impact on the environment, non-targeted organisms, and the farmer and the community (consumers).

With IPM, the farmer invests in:

• prevention,
• early detection, and
• management

However, due to the system’s complexity, there is still no certification for growers applying IPM. It is important to remember that while IPM is a sustainable strategy, the foods produced under this system are not considered organic.

The Role of IPM in Sustainable Agriculture

• Sustainable and efficient pest control: While it is a more complex pest management system, it can have long-term and higher efficiency, reducing yield losses and, in some cases, production costs. At the same time, it protects the populations of beneficial insects (crop pests’ natural enemies and pollinators),
• Products of higher quality and safety and fewer production costs → increased farmer’s income,
• Reduces pesticide residues in the food and decreases the pollution of water and soil: IPM contributes to food and water safety by reducing the amount of pesticide residues in food, feed and fiber, and the environment.

The principles of IPM

• Κnow the pests in your region and know their physiology
• Monitor your crop often and learn how to identify the different stages of the pest and the damage it causes early.
• Invest in prevention, not control. Keeping the population of the pests under control and having multiple protection barriers is the most efficient (and economical) way to avoid damage.
• Set Action Thresholds: It is the moment that the level of damage (or risk of the damage) caused by the pests (or pathogens), if left uncontrolled, exceeds the cost of the management practices.

In some cases, the action threshold is highly linked/affected by the environmental conditions, the type and physiological stage of the crop, and the pest. For example, some fresh products have very strict market quality (appearance) standards (like leafy vegetables). As a result, the farmer should take action to avoid any damage that could lead to a decrease in the quality and price of the product.

Similarly, pests like aphids can create massive populations and develop resistance to chemical pesticides in a very short period of time. As a result, on time and integrated control is necessary. Farmers are advised to follow the instructions and announcements of the local extension centers regarding the moment of control (most are based on monitoring of the pest and weather predictions).

• The use of chemical pesticides should be the last resort and should be used cautiously: Farmers are strongly advised to only use target-specific pesticides and apply all precautionary measures to protect non-target organisms (pollinators, natural enemies, etc.). It is essential to monitor the development of resistance of the pests to the chemicals used and report it.
• Always combine many IPM practices and, if possible, alter them through the years: It has been proven that a practice (even of mechanical control), when applied over and over again, can lead to the rise of resistant pathovars and species.
• Always evaluate the effectiveness of a practice or group of practices applied: This can help improve management plans and find problems of resistance early.

The different practices of an IPM program

The farmer can choose the most suitable group of measures based on the crop, the major pest threats, the environment, and the farmer’s economic and knowledge capability. He/She can choose among:

• Biological control
• Mechanical and physical control
• Cultural practices & resistant varieties
• Chemical control

1. Biological control

It includes the use of natural enemies of crop pests and pathogens to keep them under control. The ecosystem function of biological control is estimated to have an annual value close to 400 billion U.S. dollars per year compared to the 8 billion spent on insecticides.

Depending on the nature of the crop (greenhouse or open-field), the pests, and the natural enemy, the farmer may focus both on boosting populations of the natural enemies that can already be found on the field or introducing and releasing populations (purchased as a product).

In the first case, measures that invest in supporting and establishing rich agrobiodiversity can help host the beneficial insects. 

2. Cultivation practices

Modifications of planting, growing, cultivation, and harvesting practices may create conditions unfavorable for the pests and pathogens, thus decreasing their pressure on the crop. Some practices like early harvest or late planting may focus on escaping the moments when there is a higher risk of presence or increased pressure from the pathogen or pest. The use of healthy propagation material is also essential. The use of trap crops and interplanting have also been proven effective techniques long applied by farmers in many regions of the world.

In this case, measures and practices that boost agrobiodiversity are especially important.

• Use of resistant varieties: Depending on the crop and the pathogen or pest, there are some resistant or tolerant varieties available in the market. However, like for the other measure, farmers are advised to combine the use of a resistant variety with other IPM practices. The reason for this is that the pathogens when under strong selection pressure, can develop new mechanisms and manage to infect the plants (even the resistant ones). Like in the mode of action for pesticides, the resistant genes are not limitless and the breeding of a new resistant variety usually takes many years.
• The role of crop rotation in IPM: Crop rotation is one of the most efficient and widely applied practices to help in pest, pathogen, and weed management. Monocropping has helped in the build-up of the population of pests and pathogens on the field, leading to extensive yield losses or/and excessive use of pesticides and the development of pesticide-resistance problems. Rotating crops in the field with different physiological characteristics and not closely genetically related to each other can help keep the populations of pests (the same goes for pathogens and weeds) under control.

This crop diversification will:

• boost the populations of natural enemies
• reduce the survival and reproduction of the crop “enemies” by not always offering a suitable plant host
• create systems with different lifecycle lengths, nutrients, and water demands, needs for pest and disease control and cultural practices, etc. All these decrease the selection pressure on crop pests and pathogens.

The farmer should be well-informed and cautious when creating a crop rotation scheme. In case crop rotation is used as a practice of weed, pests, and disease management, it is essential that the farmer should:

• Select species that are not hosts of the same pathogens and pests (better use crops from different families)
• Decide on the number of years of rotation – this is highly related to the survival of the pathogens and pests in the absence of a host.

3. Mechanical and physical control

Mechanical control can help to kill crop pests and weeds directly, create barriers of entry to the field, and create unfavorable conditions, leading to the control of their population. Some commonly used mechanical practices are:

• Deep harrowing to expose weeds seeds and overwintering stages of the pests and pathogens.
• Mulching and steam sterilization of the soil – by covering the soil with a plastic mulch during the warmest period of the growing season increases the soil temperature, thus killing weed seeds and soil pests (e.g., nematodes) and pathogens.

Handpicking of the pests or their eggs – this may be helpful and possible only in small subsistence farms.

• Use of mechanical traps
• Remove infested plants or plant parts from the field and destroy them (e.g. shredding). It is important not to leave unharvested plants, fruits, and vegetables on the field that can function as survival media for pests and pathogens, preserving their population and leading to new infections and infestation next season.
• False seed-bed technique → efficient in controlling weeds (especially annuals)
• Fences, nets, barriers, or electronic wires can be used as physical barriers to keep birds away.

4. Chemical control

Chemical control involves the use of pesticides. Farmers are strongly advised to only use target-specific (selective) pesticides and apply all precautionary measures to protect non-target organisms (pollinators, natural enemies, etc.). It is essential to monitor the development of resistance of the pests to the chemicals used and report it.

To have the maximum, long term effectiveness of the pesticides used and decrease the negative effects to the environment and the health of the farmers and consumers, there are some guidelines that need to be followed.

Basic Principles for Effective Chemical Applications

• Mode of Action (MoA):

Each chemical has a different MoA that attacks different processes of the pest/disease. Consult with an expert to identify the most effective MoA for a specific pest.

• Rotation between Chemicals:

It is very important to rotate between various chemicals with different MoA. When using chemicals with the same MoA for treating the same pest, there is a high risk of pest resistance development. Doing it will make it harder or even impossible to control the pest in the future. Keep in mind that there are usually numerous commercial products with the same MoA or the same active ingredient. Therefore, make sure to rotate with products (e.g., pesticides) with different MoA.

• Know the way your product works:

Chemicals used in plant protection (pesticides, fungicides, herbicides, etc.) may have a contact action or systemic action. To control the crop “enemy,” it is important to know if the product you are using has a systemic action or not and how long it remains active.

• Use only locally registered products suitable for the crop of interest:

It is essential to purchase only locally registered pesticides and fungicides from licensed pesticide dealers. Make sure that the specific product is suitable to be used for the pest and the crop of interest. Always check the expiration day of the product. It is preferred not to store large quantities of agrochemicals.

• How to spray the plant:

Make sure that all parts of the plant are covered with the spray, including the lower parts and the top of the plant.

• When to apply the pesticides:
  • Spraying should be done very early morning or in the (late) afternoon (ask your local licensed agronomist).
  • Do not spray in strong sunlight hours as the spraying may scorch the plants (especially oil-based materials).
  • Do not spray when rain is expected or soon after the rain, as the moisture on the plants may wash off the chemicals.
  • Avoid spraying in days with strong winds and always spray in the wind direction (never against it).
  • Prefer pesticides that are bee-friendly. In any case, it is best to spray when the bees are not active (late in the afternoon), if possible not during flowering, and always after informing neighbor beekeepers.
  • Always respect the minimum days from the chemical application until the harvest of the product. Read the product label.

References

• • https://crops.extension.iastate.edu/encyclopedia/soil-erosion-and-crop-productivity-topsoil-thickness
  • https://www.google.com
  • Deng, C., Slamti, L., Raymond, B. et al. Division of labour and terminal differentiation in a novel Bacillus thuringiensis strain. ISME J 9, 286–296 (2015). https://doi.org/10.1038/ismej.2014.122
  • https://www.fao.org/agriculture/crops/thematic-sitemap/theme/compendium/tools-guidelines/what-is-ipm/en/
  • https://ipm.ucanr.edu/GENERAL/whatisipmurban.html
  • https://agriculture.ec.europa.eu/common-agricultural-policy/cap-overview/cmef/sustainability/ipm-toolbox-farmers_en
  • https://food.ec.europa.eu/plants/pesticides/sustainable-use-pesticides/integrated-pest-management-ipm_en
  •  https://wikifarmer.com/bacillus-species-a-green-solution-for-sustainable-crop-production/
  •  https://treefruit.wsu.edu/crop-protection/opm/mating-disruption/
  •  https://ipm.ucanr.edu/what-is-ipm/
  • https://wikifarmer.com/microbial-biopesticides-for-a-safer-and-sustainable-pest-management/
  • https://wikifarmer.com/important-beneficial-insects-as-natural-enemies-of-crop-pests/
  • https://fwwa.org/2017/05/31/crop-rotation-systems-soil-erosion-reductions-increased-water-quality/
  • https://www.fao.org/3/i3482e/i3482e03.pdf
  • https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/agroforestry