Fruit – Lesson 2: Biopesticides

Pressure to reduce the use of chemical plant protection products is prompting more growers to turn to biopesticides to control pests and diseases.

In this lesson you will learn:

  • What are biopesticides?
  • How biopesticides work
  • Legislation
  • Benefits of biopesticides
  • Getting the best from biopesticides
  • Integrated Pest Management

On top of pressure from retailers and the public to cut the use of chemicals in crop production, there is also a large reduction in the choice of conventional plant protection products now available to growers.

This means biopesticides are steadily becoming an increasingly important element in farmers’ and growers’ crop protection armoury. As interest increases, manufacturers are investing in more research and development to create more products.

What are biopesticides?

Biopesticides are biologically-based agents used as plant protection products. They can be micro-organisms, botanicals or semiochemicals.

Micro-organisms:
Bacteria
Fungi
Viruses
Can be any microbiological entity

Botanicals:
Derived from plant materials (roots, seeds, foliage etc)
Can be simple or complex in its form
Collected from all over the world

Semiochemicals:
Produce a behavioural reaction in another organism
Pheromones from insects like moths and butterflies can be used to lure pests.

MAPP number

Biopesticides go through a very similar regulatory process to conventional chemical pesticides. They must first have the active ingredient approved at EU level and, if approved for use in the UK, they will be issued with a MAPP number on the product label.

How biopesticides work

Due to the diverse nature of biopesticide products, there are many ways in which they work. Many of these products have multiple mechanisms, while others have a single mode of action.

Biopesticides can be generally identified in one of the groups below:

Physical action
This type of biopesticide works on contact of the organism and can damage the cell membrane of the fungus or the outer body of the insect. This physically impacts the pest performance and ultimately ends in the death/destruction of the pest.

Cross-protection
A mild version of a virus is used to inoculate the susceptible crop and induce resistance to more aggressive versions of the same virus. Currently this is not in common use in the UK.

Induced Resistance
A biopesticide is used to stimulate the crop’s general protection to pathogen attack. This can be on a local level or can be systemic throughout the entire plant.

Mycoparasitism or hyper-parasitism
These introduce a parasitic bacterium or fungus, which attack a pathogen of the crop plant. Applying a bacteria-based product can degrade the spores of the pathogen as it tries to establish on the surface of the crop.

Competition
Some biopesticides are used to out-compete plant pathogens for space or resources on the crop plant. This reduces the capability for the pathogen to develop on the surface of the crop.

Wide choice for use in fruit

There is a wide range of biopesticides available for use in UK-grown fruit crops from a number of manufacturers. A list of products, the pests and diseases they control along with other information is available here

CONTINUE LESSON

Get the best from biopesticides

Storage

  • The use-up date, storage instructions and how long an opened container will keep for will be clearly instructed on the product label. This information is particularly important to follow for any micro-organism-based product
  • Most micro-organisms and some botanicals will be damaged by freezing
  • Storing in an ambient pesticide store will be suitable for most products as long as it is protected from temperature extremes
  • Some biopesticides may require storage in a fridge.

Product application

  • Most biopesticides approved for use in fruit crops are contact-acting so it is key to achieve total crop coverage when spraying. This can include the undersides of leaves, inside flower parts, around berries and bunches of fruit
  • Select the correct nozzle, water volume and forward speed to achieve best coverage
  • Some products may require specific nozzle types to prevent blockages
  • For products applied via a drench/fertigation system the correct concentration needs to be calculated
  • The water used for application needs to be clean and not treated with any chlorine or other disinfectants that have residual activity
  • Some products can be applied to roots prior to planting – check label instructions for guidance.

Application frequency

  • Most products have a relatively short persistency once applied to a crop
  • Soil applied/incorporated products are an exception because of their reduced exposure to sunlight
  • Where there is a constant pressure from a disease (powdery mildew in strawberries for example) regular applications, at 7-day intervals, may be necessary to maintain adequate protection
  • Biopesticides are often used in conjunction with conventional chemical pesticides, sometimes in sequence and sometimes mixed together to maintain protection over a high-pressure period.

Environmental conditions

  • Ensure the sprayer tank is thoroughly cleaned, using a rinse aid – such as All Clear Extra
  • The weather and growing conditions will influence the efficacy and persistency of the product – just like any plant protection product
  • Avoid applying biopesticides during the hottest part of the day, ideally apply in the evening
  • Products are not systemic or rainfast, do not apply before a heavy rain event (if not growing under protection)
  • Some products may need to be applied with a UV-protectant to maintain their persistency on the leaf
  • Do not apply products at temperatures below 10°C or above 30°C
  • Repeat applications may be required when pest or disease population is increasing.

Operator tip: Micro-organism viability can reduce if the label recommendations are not followed. This can result in reduced efficacy because the product will not work at its best.

Quick Quiz: Strengths and weaknesses

Sort the following statements into whether it is a strength or weakness of a biopesticide.

Tank Mixing

  • Many strains of micro-organisms have been selected for their compatibility with some conventional chemical pesticides, on the same target crop
  • Some products will be able to tank mix with chemical pesticides
  • Check the label or ask your agronomist for advice
  • If no guidance is available, then apply the biopesticide on its own
  • Some biopesticides labels recommend an interval of a few days between their use and that of a conventional chemical pesticide.

Adjuvants and biopesticides

  • Some products stipulate the use of an adjuvant to improve performance – for example product label information above
  • Some biopesticides can work better with the assistance of an adjuvant
  • This is mainly because many biopesticides are contact-acting and, to work effectively, rely on total crop coverage.

Timing of use

  • Some products will advise application before or at the onset of disease/pest presence
  • To achieve a disease reduction some products require multiple applications before the disease symptoms occur, rather than just a single protectant treatment 
  • Following applications will be dependent on pest/disease pressure, noted from regular crop inspections
  • If results are still not achieved, consider reducing the interval (where permitted) or switch to an alternative product with a more immediate effect on the population level
  • Also consider the lifecycle of the target pest/disease, some products are best applied at a specific timing
  • Some products work best when the humidity is high (AQ10, Naturalis-L).

Biopesticides can be best to use when close to the expected harvest date as they inherently have short harvest intervals.

Quick Quiz: Best use

Test your knowledge about getting the best from using biopesticides. Use the lesson content above to check whether the following statements are true or false.

CONTINUE LESSON

Biopesticides boost Integrated Pest Management

Biopesticides can play an important role in Integrated Pest Management (IPM), helping to reduce reliance on chemical controls. This helps to protect beneficial insects, offers a much lower risk of resistance and proven low environmental impact.

This means when planning control of pests and diseases, it’s vital to begin with investigating the use of a biopesticide as an alternative to chemical-based crop protection products.

Well done, you have reached the end of Lesson 2 – Biopesticides and you now need to complete the end of lesson test. You should not move on to the next lesson, until you take this test. You will need 80% to pass. You can re-sit the test as many times as it takes to pass. Once you have passed this test, you can move on to lesson 3.

To start the test, click on Fruit: End of Lesson 2 Test (Compulsory) below: