Pesticides play a sensitive role in food systems: they are applied in order to protect crops, but they can have negative impacts on environment and human health. While global pesticide use has grown to 3.5 billion kg active ingredients per year, a significant portion of the chemicals applied has proved to be excessive, uneconomic or unnecessary both in industrialized and developing countries.
Today there is a consensus among a wide range of stakeholders that pesticide use needs to be gradually reduced to a level that is effectively required to ensure crop production, and that risks of pesticide application need to be reduced as far as possible.
Here are listed 7 strategies available for pesticide reduction.
1. Agronomic practices.
Suitable agronomic practices are essential to achieve healthy crops and to prevent build-up of pest, disease and weed pressure. The following practices are of particular importance:
- Appropriate plant nutrition and soil fertility management;
- Crop rotation;
- Appropriate irrigation management;
- Appropriate timing of sowing or planting and of intercultural operations in order to reduce pest;
- Timely shallow tillage reduces weed populations and at the same time improves nutrient supply to the crop;
- Precision farming like spraying of hot-spots and weeding with optical detectors;
- Intercropping (when it is possible) and the use of variety mixtures limits the spread of pests and diseases and provides food and shelter for natural enemies of pests;
2. Resistant crops
Crops and crop varieties differ in their susceptibility to pests and diseases and in their ability to compete with weeds. Growing crops suitable for local conditions and selecting appropriate crop varieties is therefore fundamental to a preventive pest management system. The use of resistant varieties together with rotations of non-susceptible crops can substantially limit pest build-up within a field.
3. Bio-control and Natural Pesticides
Bio-control makes use of pathogens (bacteria, fungi, viruses), insect predators or parasitoids, pheromones and insect traps to keep pest populations low.
The total eradication of a pest, which results from the use of synthetic pesticides, would reduce the food supply of the pest’s natural enemies, undermining a key element in system resilience. The aim, therefore, should be to manage insect pest populations to the point where natural predation operates in a balanced way and crop losses to pests are kept to an acceptable minimum.
4. Integrated Pest Management (IPM)
IPM is an ecosystem approach that does not seek to eradicate pests – but rather to manage them. It is founded on the idea that the first and most fundamental line of defense against pests and diseases in agriculture is a healthy agro-ecosystem, in which the biological processes that underpin production are protected, encouraged and enhanced.
A close approach to these principles is the common GlobalG.A.P. protocol even if it is not totally focused on pest prevention. The majority of retailers in today’s markets require certain standards that ensure safe and sustainable agriculture for demonstrating on-farm food safety and sustainability.
In a true IPM strong focus is on pest prevention by applying good agronomic practices and using resistant varieties, pest identification and monitoring and biological pest control. As soon as the economic threshold is achieved – the point at which the cost of pesticide use pays off (cost of expected loss in harvest exceeds the cost of treatment) – chemical pest control becomes profitable. The last step includes learning and adapting from IPM for the next crop season.
5. Agroecology
Agroecology is a discipline that defines, classifies and studies agricultural systems from an ecological and socio-economic perspective, and applies ecological concepts and principles to the design and management of sustainable agroecosystems. It is an integrative way of farming that focuses on working with and understanding the interactions between plants, animals, humans and the environment. In Agroecology pest control seeks to reinforce interactions of pests and natural enemies with the aim to maintain a natural balance in the ecosystem. While there is no consent on what techniques and inputs are compatible with agroecology the common denominator is to make use of biodiversity-based ecological processes to optimize agricultural production systems.
6. Organic Agriculture
Organic agriculture is a production system that sustains the health of soils, ecosystems and people. It relies on ecological processes, biodiversity and cycles adapted to local conditions, rather than the use of inputs with adverse effects. Organic standards strictly prohibit any use of synthetic pesticides. Crop protection in organic agriculture builds on good agronomic practices such as crop rotation and intercropping, the use of organic manures, resistant varieties and bio-control to prevent that pest, diseases and weeds cause significant damage.
Organic farming makes use of techniques similar to Integrated Pest Management and agroecology, with the only difference that synthetic chemicals cannot be used as a last resort.
Instead, organic farmers can use specific natural substances permitted by organic standards to control pests and diseases if preventive methods are not sufficient. Some of them, however, also have unwanted side effects on non-target organisms. Particularly the use of copper to control fungal diseases is problematic due to its accumulation in soils.
7. Use of less hazardous pesticides
There are various systems to classify pesticides as per their toxicity for humans and the environment. Phasing out the use of highly hazardous pesticides and replacing them with less hazardous ones is therefore the most obvious way to reduce the negative side-effects of pesticides.
This approach needs to be combined with safe handling of pesticides so that their impact on people and the environment is minimized. The use of protective gear and the observation of waiting periods before harvest are the most important measures in this regard.
However, in many countries the lack of information, unavailability of protective equipment and its impracticality in hot and humid climates result in low adoption rates.
Source: Frank Eyhorn, Tina Roner, Heiko Specking September 2015
