Biopesticides: Natural alternatives to toxic chemicals for pest and disease control

Throughout the 20th century, the use of chemical pesticides was widely adopted in agriculture to control insect pests, weeds, and plant diseases. However, many of these pesticides are now known to be harmful to human health and the environment, leading numerous countries to ban large numbers of these products from being used. 

This poses the question – how will farmers protect their crops, if these products are banned? In fact, a range of solutions already exists, in the form of biological alternatives. 

An important distinction between conventional chemical pesticides and biological alternatives is the fact that, while you might think of pesticides as something that kills pest insects, some biopesticides aim to control – rather than obliterate – them. This gentler approach provides a more selective effect that does not affect beneficial insects and is harmless to the surrounding environment.

This guide will teach you how biological alternatives use nature itself against insect pests to provide effective control, instead of spraying our crops with toxic chemicals that are potentially harmful for humans and animals alike.

What are biopesticides?

The term "biopesticide" was coined in the 1980s and refers to natural, biological substances used for pest control. The past few decades have seen various academic debates about the definition of a ‘natural’ pesticide, but more recently the sector has started to consider definitions based upon their effects, rather than their origin or makeup. 

In summary, a true biopesticide must have one or both of these characteristics:

1. A pesticidal effect caused by a naturally occurring substance or its synthetic equivalent, which is derived from a plant or animal source (or mined);

2. A pesticidal effect induced through biological means — for example, by using a microbial pesticide to target an insect pest's gut bacteria.

Classes of biopesticides

There are four types of biopesticides:

1. Microbial pesticides contain an active element which is a microbe (bacteria, fungus, virus or protozoan). Although each active ingredient is somewhat particular for its target pest[s], microbial pesticides can control a wide range of pests. There are fungi that control weeds, and other fungi that kill specific insects, for example.

   
   

   Bacillus thuringiensis, or Bt, subspecies and strains are the most frequently used microbial insecticides. Each strain of this bacterium creates a unique combination of proteins that kills only one or a few closely related insect larvae. While some Bt compounds are effective against moth larvae on plants, others are only effective against flies and mosquito larvae. The target insect species is chosen by whether or not the Bt generates a protein that binds to a larval gut receptor, causing the larvae to starve.

   
   

2. Macrobials contains invertebrate biocontrol agents such as ladybirds, dragonflies and insect-parasite nematodes

   
   

3. Biochemical pesticides are naturally occurring compounds that use non-toxic ways to control pests. (Conventional insecticides, on the other hand, are usually synthetic compounds that kill or inactivate the bug directly.) Biochemical pesticides include insect sex pheromones and other scented plant extracts that attract insect pests to traps, or interfere with mating. 

   
   

4. Plant-Incorporated-Protectants (PIPs) are pesticidal chemicals produced by plants from genetic material introduced into the plant. Scientists can, for example, extract the gene for the Bt pesticidal protein and insert it into the plant's genetic code. The plant then produces the chemical that kills the bug instead of the Bt bacteria. The EPA regulates the protein and its genetic material, but not the plant itself.

How biopesticides work

Biopesticides can have one (or more) of the following modes of action:

• Kill on contact

• Kill after ingestion

• Repel

• Inhibit feeding

• Inhibit growth

• Inhibit reproduction.

Advantages of using biopesticides

In general, biopesticides are less hazardous than conventional pesticides. In contrast to broad-spectrum, conventional chemical pesticides, which can harm creatures as diverse as birds, insects, and mammals, biopesticides usually affect only the target pest.

Biopesticides are frequently effective in small amounts and they disintegrate quickly, resulting in smaller exposures and avoiding the pollution problems that conventional pesticides produce.

Biopesticides, when utilised as part of Integrated Pest Management (IPM) programmes, can significantly reduce the usage of conventional pesticides while maintaining good crop yields.

However, in order to utilise biopesticides successfully (and safely), users must have a thorough understanding of pest management and must strictly adhere to all label instructions. 

A Highly Targeted Approach to Crop Protection

Selectivity is one of the most significant differences between bioactive crop protection agents and conventional agrochemicals. Traditional agrochemicals are often broad-spectrum agents that affect a wide range of species. These products help farmers to control multiple pests with a single pesticide, but they can also affect non-harmful species in the ecosystem, pollute waters and soils, and damage human health.

Biopesticides are usually quite selective in their target pests. They are often believed to be more environmentally friendly than synthetic agrochemicals since they are so targeted. Bacillus thuringiensis (Bt), for example, is a bacterium often employed as a microbial pesticide that comes in a variety of strains and subspecies, each of which kills a single insect or a few closely related insect species. Each Bt strain produces a protein that is highly specific to the target insect species and non-toxic to other organisms (including humans and animals).

Why haven’t biopesticides replaced conventional pesticides?

When biopesticides were first available in the 1980s, farmers tried to use them like conventional agrochemicals. However, in order to work properly, many biopesticides need to be applied at certain temperatures, or require particular attention to tank mixing. Above all, because biopesticides are so selective to target pests, the right product must be chosen to control those pests. Unfortunately, mis-application of early biopesticides meant that they did not work as well as they could. Growers need training to utilise biopesticides efficiently and to use different treatments to control different types of pests and pathogens, because they are highly targeted. When used correctly, biopesticides can be least (sometimes more!) effective as conventional agrochemicals. 

Biopesticides also face issues such as preserving microbial viability during storage, and compatibility with chemical pesticides. Advances in formulation are prolonging the shelf life of blended products and improving their compatibility. In addition, advancements in delivery are opening up new avenues for biopesticide application.

Finally, although numerous biological products are already available, many more are still in development and until they are ready to reach the market there are some pests for which no biological options are yet available. In those circumstances, for which a natural alternative is not yet on the market, a synthetic agrochemical is often the sole option.

In conclusion

Bionema is working to provide farmers with new and more effective biopesticides. For more information on Bionema's biopesticides range of products, formulation and world class delivery for horticulture, sport turf, forestry, and public health please reach out to us.