PESTICIDES

A pesticides job is to make sure plants and gardens are protected by removing pests. This can be in the form of herbicides, insecticides and fungicides which all tackle a different kind of pest. Chemical pesticides are under strict regulation in the UK and EU with some of the most environmentally damaging ones being banned in these regions.

However, there are still many problems with chemical pesticides getting into the natural system. Contamination of these chemicals easily occurs through field run off, improper disposal and when sprayed aerially, potentially killing/ damaging local wildlife.  Another concern is with synthetic pesticides and issues with them attacking other, unintended organisms, impacting the wildlife in and near gardens.

Pros

– The UK has strict regulations regarding the use and sale of pesticide products which are enforced by the Health and Safety Executive (1).

– Can protect native ecosystems form foreign diseases that they aren’t adapted to fight against like gypsy moth and emerald ash borers (2).  

– Natural , or sometimes known as organic pesticides such as garlic oil or Kaolin clay are a more environmentally friendly option for pest removal (4). Although there is always the risk of damaging beneficial wildlife, such as worker bees.

– Some species have no natural predators, and a pesticide is the only solution to getting rid of them and maintain plants in a good condition (3).

Cons

–Surface water contamination occurs from the runoff of treated plants and soils, in significant concentrations this can cause the decline in fish and other organisms (6).

–Harsh chemicals that kill a wide range of organisms not just specifically pest are causing biodiversity to be reduced in gardens, limiting potential wildlife (4).

–Resistance to pesticides- there is an increasing amount of pests and diseases that cannot be controlled by chemicals as they have built up a resistance to them, meaning alternative methods / stronger chemicals may need to be used causing further harm to the environment (3).

–Poisoning up the food chain is a problem when a larger animal such as a bird is harmed by consuming an organism, e.g., a worm  that has been poisoned by pesticide (7).

–Pollinators such as bees and butterflies are being effected by pesticides either through direct contact (spraying) or from contaminated sources (nectar, pollen or water) (4).This is due to pesticides not being specific in which organisms they target meaning beneficial insects are being harmed.

–Pesticides are contaminating even people now with a study from 2014-2021 across 5 European countries finding at least 2 pesticides in the bodies of 84% of the participants (5).

Neonicotinoids

Neonicotinoids are the most commonly used insecticide in the world although they have been found to have devastating ecological impacts (14). They work by permanently binding to the nerve cells of invertebrates causing them to be overstimulated and destroyed paralyzing the insects before they die (15).  However, they cannot target specific insects so beneficial pollinators like bees can also be harmed. Neonicotinoid insecticides can be applied directly to the soil or covering a plant seed in so as the plants grow the chemical is soaked up making the plant itself toxic (in the leaves, nectar, roots etc). The ecological concerns come from these toxins leaking into the environment as they can remain active in the soil for months to years after being applied (15). This increases the chance of leaching into water systems and contaminated dust spreading from wind erosion.  Three types of neonicotinoids were banned from the use in the UK in 2018 for causing harm to bees and other important insects (16). However, one kind (acetamiprid ) is still authorised for use, in insect sprays for homes and gardens ( BugClear Ultra and RoseClear Ultra).

Natural Pesticide Options

Pesticides aren’t the only option to solve the problem there are different strategies as well as natural options that can help reduce pests.

Biological control:

This is the process of using natural predators, parasites or pathogens to manage pests as an alternative to pesticides (8). Biological control can specifically target types of plant damaging invertebrates compared to pesticides killing a wide range of them. Predators such as ladybirds, lacewings or predatory mites can be used to feed on harmful pest, but they don’t instantly reduce the prey population as time is needed for them to reproduce (9). Nematodes are another type of biological control which are important to soil and marine ecosystems, however a large amount of the >25,000 species are parasitic to plants and animals so there has been development into using them as biological controls (9). They can be bought online or form garden centres and should be used soon after purchase as they are living organisms.  

Integrated pest management (IMP):

IMP is often used my commercial growers but can be used in home gardens as well. It involves a mixture of methods like, biological control, rotation of plants, promoting natural predators and parasites of common pests and when needed using chemical agents, although in home gardens there is much more opportunity to use natural alternatives (10).

Natural alternatives:

–Vegetable oil spray – mix 1 cup of vegetable oil with a tablespoon of soap (11). Dilute with around 950ml of water before spraying directly on affected plants (should avoid heat of the day as can damage water stressed plants). It is effective in aphids, mites etc, as the mixture coats the insects meaning they can’t breathe (12).

–Neem oil spray– mix 2 teaspoons of neem oil with 950ml of water then spray on affected plant foliage early in the morning or evening to avoid foliage burn (11).  It disrupts the life cycle of insects at any stage of life and is safe for pets, birds, fish, and beneficial insects like bees, butterflies, and ladybugs. Neem oil is effective against common pests and  acts as a fungicide against fungal infections like powdery mildew (13).

–Diatomaceous earth– is a made from sedimentary rock containing fossilized algae (diatoms), which have abrasive qualities and are good at absorbing liquids from an insects exoskeleton, dehydrating them (12). It targets crawling insects like slugs and should be sprinkled on the ground or directly affected leaves, and reapplied after rainfall (11).   

Sources

  1. https://www.hse.gov.uk/pesticides/about-pesticides.htm
  2. https://www.gardeningknowhow.com/gardening-pros-cons/pesticide-and-herbicide-pros-and-cons
  3. https://www.rhs.org.uk/prevention-protection/chemicals-using-them-in-gardens
  4. https://xerces.org/sites/default/files/publications/13-053_web-screen.pdf
  5. https://www.eea.europa.eu/publications/how-pesticides-impact-human-health
  6. Aktar, W., Sengupta, D. and Chowdhury, A. (2009). Impact of Pesticides Use in agriculture: Their Benefits and Hazards. Interdisciplinary Toxicology, [online] 2(1), pp.1–12. doi:https://doi.org/10.2478/v10102-009-0001-7.
  7. https://www.pan-uk.org/our-environment/
  8. https://biocontrol.entomology.cornell.edu/what.php
  9. https://www.rhs.org.uk/prevention-protection/biological-control-garden
  10. https://www.rhs.org.uk/prevention-protection/chemicals-using-them-in-gardens
  11. https://www.slc.gov/sustainability/pesticidefree-2/alternative-pesticides/
  12. https://www.treehugger.com/natural-homemade-insecticides-save-your-garden-without-killing-earth-4858819
  13. Duke, S.O., Cantrell, C.L., Meepagala, K.M., Wedge, D.E., Tabanca, N. and Schrader, K.K. (2010). Natural Toxins for Use in Pest Management. Toxins, [online] 2(8), pp.1943–1962. doi:https://doi.org/10.3390/toxins2081943.
  14. https://www.xerces.org/pesticides/understanding-neonicotinoids
  15. https://www.nrdc.org/stories/neonicotinoids-101-effects-humans-and-bees
  16. https://www.pan-uk.org/about_neonicotinoids/