Recently, there is more and more concern about the use of chemical pesticides and herbicides and their impact on our health and climate. The industry has been looking for alternative methods and this has led to more research on biological pest control agents.
Description of the innovation
Nature has its protection mechanism against naturally occurring enemies (bacteria, insects, fungi, and viruses). This results in a natural balance. These natural enemies can be predators, parasitoids, or pathogens. However, this defence mechanism is not always sufficient, making it necessary to use products such as pesticides. Pesticides are widely used in agriculture with the aim to reduce crop losses, by insects, weeds, or microbial plant pathogens and thus promote the productivity of the plant. Pesticides represent a wide range of chemicals with many environmental effects. Some are easily mineralised in the soil, however others are quite persistent. On the one hand, biodiversity can be influenced negatively, and on the other hand, target organisms can develop resistance to pesticides. Pesticide resistance may even be a human health risk in some cases.
As chemical pesticides not only harm the ‘pest’, we need to look more to biological solutions. This will benefit biodiversity, plant health, and soil content. Biological pest control aims to suppress pests and diseases while respecting environmental considerations.
Reducing pesticide use
Trap crops are plants that attract or repel certain pests to protect the main crop. They may not only attract, but also disrupt the lifecycle of some pests, or eliminate viral vectors in some insects.
Several factors should be taken into account: both plants should have similar requirements for growth, the spatial location related to the main crop, and timing. Trap crops can be planted on the perimeter of the main crop, or as an intercropped crop. In potatoes, it has shown that planting trap crops of the same family before or after (sequential crop) the main crop helped control nematode cysts. These crops produce a series of compounds that cause the cysts to hatch but do not support the oviposition of the pest, reducing its presence in the soil.
Another technique is the ‘push and pull’ technique. Here an unattractive crop is planted in between the main crop to repel the pest, while an attractive crop is planted in the perimeter of the main crop.
Some trap crops can also attract natural predators for the pest, explained further in ‘Biopesticides – macrobials’.
The market for agricultural biologicals is growing fast lately. It is forecasted it will be tripled by 2026 (from 2018). The demand is driven by the need for new innovations in the food sector, as well as an increasing demand for agricultural sustainability, consumer perspective on organic farming, weed and insect resistance to chemicals, and concerns about the environment related to the use of chemicals. Biopesticides may be complementary to conventional solutions, as well as an alternative solution. Biopesticides are interesting because they facilitate integrated pest management and protect beneficial organisms, including pollinators, as they affect only the target pest. They are also important for resistance management, and have very low toxicity. A few of the key players in the market are BASF, Syngenta and Bayer.
Biopesticides (plant protection or biocontrol products) represent a broad category of plant protection products that are derived from living organisms:
- Microbials are living micro-organisms (MO) like bacteria, viruses, fungi, or protozoa. Microbial pesticides can control many different kinds of pests, although each separate active ingredient is relatively specific for its target pest[s]. For example, there are fungi that control certain weeds and other fungi that kill specific insects. The most widely used microbial pesticides are subspecies and strains of Bacillus thuringiensis (Bt). Each strain of this bacterium produces a different mix of proteins and specifically kills one or a few related species of insect larvae.
- Macrobials are beneficial insects and nematodes. Some nematodes (genera Heterorhabditis, Steinernema, Phasmarhabditis) are used to control snails and insect larvae (May and June beetles, vine weevils, leatherjackets,...). Nematodes may also cause damage in grassland and fodder crops depending on the species and number. Crop rotation and the whole of a healthy soil with a high biodiversity of nematodes and other organisms are therefore also very important.
A well known insect for the control of aphids is the ladybird. It is highly effective and has a high reproductive rate.
- Biochemical pesticides are naturally occurring substances that control pests by non-toxic mechanisms. They include substances that interfere with mating, such as insect sex pheromones, as well as various scented plant extracts that attract insect pests to traps.
- Plant-Incorporated-Protectants (PIPs) are pesticidal substances that plants produce from genetic material that has been added to the plant.
Using biopesticides comes with several challenges. They have a lower efficacy, due to inferior active ingredients, the suboptimal usage recommendations, and lack of knowledge available.
In the last few years, research is done on the use of RNAi (RNA interference) as crop protection against various insects. Specific selected RNA can interfere with protein synthesis in the insect, which causes mortality. Due to the specific mode of action, the product stays inactive to closely related species. This makes it safe and has a reduced risk against other beneficial insects. The products need to be ingested by the insect (only surface contact is not enough), so spraying this using existing agronomic practices is possible.
RNA molecules are labile, which makes them highly biodegradable. This can be a disadvantage if the pest is present in a harsh environment. The biological environment of the soil, for example, contains many microbes and nucleases, which leads to the rapid degradation of unprotected RNA. So, the RNA should be available for several weeks.
Several pests showed high sensitivity to RNAi: corn rootworm (SmartStax Pro), Colorado potato beetle, and soybean stinkbug.
Figure 2. Application of RNA-based biocontrols in crop protection (Source: Bramlett et al. 2019)
Another use of RNAi is inducing virus resistance and gene silencing in plants. As genetically modified crops are limited consumed, this can be an alternative route. By RNAi, crops can become resistance to certain pests, and overcome the ill effects of pests and pathogens.
It is included in the Farm-to-Fork strategy that “a micro-organism can only be approved for use if it is proven that it does not cause disease in humans or animals. Microorganisms are naturally occurring and most of them are harmless. Many of them play key roles in the ecosystems, for instance by decomposing organic matter in the soil to make it available for other organisms, or by enriching the soil with atmospheric nitrogen (“nitrogen fixation”) to make it available for plants. Currently, more than 60 microorganisms are approved in the EU after a scientific risk assessment confirmed that their use in plant protection products is safe. Microorganisms are also crucial for Integrated Pest Management (IPM), which farmers have to use in the EU. Farmers must give preference to preventive actions, monitoring and biological plant protection alternatives (including micro-organisms based products), before using chemical plant protection products.”
According to the FAO, the use of biopesticides is interesting and will work best in a holistic approach. Best is to focus on preventing, rather than curing a large-scale outbreak. Changing from pesticides to biopesticides however, is not that easy. They are more complicated to use in terms of transportation, storage and mixing. This requires more training than the use of the conventional pesticides.
Impact on-farm performance
Socio-economic resilience: Trap crops: determine economic efficiency of this type of management
Animal health and welfare: Reducing chemical pesticide use also reduces the risk of toxic residues ending up in the animal feed.
Production efficiency and meat quality:
Environmental sustainability: (soil) biodiversity will be improved
Regulation (EC) No 1107/2009 of the European Parliament and of the council of 21 October 2009, concerning the placing of plant protection products on the market and repealing
Biologicals: Naturally protecting crops
Biologicals: the next agricultural technology revolution
What are biopesticides?
Biopesticides: market insights
Bramlett M. et al (2019). RNA-Based Biocontrols—A New Paradigm in Crop Protection
Soto-Goméz D. et al (2020). Interactions between agricultural management and soil biodiversity: An overview of current knowledge
Kumar J. et al (2021). An Overview of Some Biopesticides and Their Importance inPlant Protection for Commercial Acceptance