Pro Life vs Anti Life: A Case for and Against Pesticides in the Landscape

The use of pesticides and chemical controls in horticulture is a contentious issue, particularly within the realms of landscape design and maintenance where environmental values are being prioritised more than ever before. These substances have both staunch proponents who highlight their benefits and critics who underscore their drawbacks.

Below is an expanded analysis designed to offer tangible insights for landscape designers and maintenance crews.

Pro Life

Fundamentally, we can say that focusing on pest control without using pesticides is a “pro life” approach. We focus on biological controls (which we’ll discuss later), and this is a similar approach to taking probiotics for our own health as humans.

Predatory insects and soil microbes are both example of the “pro life” approach to pest control.

Anti Life

To further this analogy, we can think of pesticides as performing a similar function to antibiotics (which means “anti life”). They might be needed in special circumstances to improve plant health and remove a serious pest or disease from a landscape, but they’re not a great long-term approach.

While they definitely have a place in modern horticulture, it’s often best to leave chemical controls for a last resort.

Pros of Using Pesticides and Chemical Controls

Effective Pest Management

• Pesticides are highly effective in controlling a broad spectrum of pests, including insects, weeds, fungi, and bacterial pests, which are common in landscape settings.
• For instance, insecticides can quickly address infestations of aphids, caterpillars, and beetles, safe-guarding the health and longevity of ornamental plants. (There are two sides to this argument, so keep reading.)

Increased Productivity

• By minimising pest populations, chemical controls contribute to increased productivity and efficiency in maintaining landscapes.
• Herbicides can significantly reduce the time and labour required for manual weeding, allowing crews to focus on other tasks such as planting and pruning.

Cost-Effectiveness

• When applied correctly, pesticides represent a cost-effective solution for pest management, reducing the economic losses associated with pest damage. Particularly in a production or nursery setting, but also in landscapes where dead plants must be replaced.
• For example, pre-emergent herbicides can prevent weed germination, saving costs on repeated weed control measures throughout the growing season.

Improved Crop Quality

• Chemical controls help maintain the aesthetic quality of ornamental plants by preventing pest-induced damage and disease.
• Fungicides, for instance, can protect roses from black spot disease, thus preserving their ornamental value.

Flexibility and Rapid Action

• Many pesticides provide rapid action against pests, offering immediate relief and flexibility in addressing specific pest issues.
• Systemic insecticides, which are absorbed by plants and protect them from the inside out, can be particularly useful for persistent or hidden pests.

Cons of Using Pesticides and Chemical Controls

Environmental Impact

• Pesticides can have severe environmental repercussions, affecting non-target organisms, including beneficial insects such as pollinators and predators, birds, and aquatic life.
• Runoff from treated areas can contaminate waterways, leading to broader ecological imbalances and harming fish and amphibians.
• Reduced numbers of beneficial organisms, such as predatory beetles and parasitoid wasps, can provide an improved environment for pest insects which form the bottom layer of the food chain and are necessary to build beneficial insect numbers.

Human Health Risks

• Exposure to pesticides poses health risks to those applying them and to the public, including acute poisoning and long-term chronic illnesses such as cancer and neurological disorders. The science can be confusing around these chemicals, so avoiding their use is usually the safest approach.
• Proper training and protective equipment are essential to mitigate these risks, but accidental exposure can still occur. There have been many times the “o-ring” on the cap of a backpack sprayer has busted without me knowing, leading to chemicals dripping down my back.

Pest Resistance

• Over-reliance on chemical controls can lead to the development of resistant pest populations, making these chemicals less effective over time and necessitating higher doses or new formulations.
• Integrated pest management (IPM) strategies that combine chemical, biological, and cultural methods can help slow resistance development. We’ll discuss this later, but a good cultural control in an IPM plan could include “sacrificial crops” that allow for pests to breed with the resistant pests, thereby negating any resistance that is bred into pest populations.

Soil Degradation

• Continuous pesticide use can degrade soil health, reducing its fertility and disrupting the microbial balance necessary for healthy plant growth.
• Soil-applied herbicides and any type of fungicide (apart from probiotics) can particularly affect soil structure and microbiota, impacting plant nutrient uptake and overall soil health.

Biodiversity Loss

• The widespread use of pesticides can result in a decline in biodiversity, as non-target species often suffer unintended consequences.
• This loss of biodiversity can have cascading effects on ecosystems, reducing resilience and the capacity to recover from disturbances.

List of Chemical Control Types

Insecticides: Chemicals designed to kill or manage insect populations.

• Examples: Organophosphates (e.g., malathion), Carbamates (e.g., carbaryl), Pyrethroids (e.g., permethrin), Neonicotinoids (e.g., imidacloprid).

Herbicides: Used to control unwanted vegetation and weeds –

• Types: Glyphosate (non-selective, systemic), Atrazine (selective, pre-emergent, and post-emergent), 2,4-D (selective, broadleaf weed control).

Fungicides: Aimed at controlling fungal infections in plants.

• Common fungicides: Chlorothalonil (broad-spectrum), Mancozeb (multi-site activity), Copper sulphate (organic option, but make no mistake – just because it’s “organic” that doesn’t mean it’s good for soil biota).

Rodenticides: Target rodents that can damage crops and spread disease.

• Used examples: Warfarin (anticoagulant), Bromadiolone (second-generation anticoagulant), Brodifacoum (highly potent anticoagulant).

Bactericides: Specifically designed to control bacterial infections in plants.

• Examples: Streptomycin (antibiotic), Copper-based bactericides (broad-spectrum, also fungicidal).

Miticides (Acaricides): Used to manage mite populations.

• Common chemicals: Abamectin (derived from naturally occurring soil bacteria), Bifenthrin (synthetic pyrethroid).

Nematicides: Target nematodes (parasitic worms affecting plant roots).

• Examples: Methyl bromide (broad-spectrum fumigant), Aldicarb (systemic insecticide and nematicide).

Integrated Pest Management

Integrated Pest Management (IPM) is a holistic approach to pest control that combines multiple strategies to manage pest populations in an environmentally and economically sustainable manner. The aim is to minimise the use of chemical controls while maximising the effectiveness of other methods. Below are the key components of IPM:

Genetic Methods

Right Plant, Right Place: This principle involves selecting plant varieties that are naturally resistant or tolerant to pests and diseases. By choosing plants well-suited to the local climate, soil conditions, and pest pressures, landscape designers can reduce the likelihood of pest outbreaks.

Using well-bred cultivated plants that possess traits for pest resistance is another genetic method of pest control. If you expect a particular pest will be present in the landscape, opt for resistant varieties instead of those prone to attack.

Cultural Methods

Environmental Management: Cultural practices focus on creating a landscape environment that discourages pest establishment and proliferation. This includes proper site preparation, removing pest-prone plants, diverse plant communities, and maintaining optimal plant health through appropriate watering, fertilisation, and maintaining airflow.

Sanitation: Removing plant debris, fallen leaves, and diseased plants helps prevent the spread of pests and pathogens. On the other hand, dead plant material is beneficial for many organisms, so you need to weigh up the pros and cons of sanitising a space. Sometimes, you’re better off leaving pest-affected plants to encourage beneficials.

Biological Methods

Predators and Parasitoids: Introducing or encouraging natural predators and parasitoids can effectively control pest populations. For instance, assassin bugs can feed on beetle pests with hard shells, while parasitic wasps can target soft-bodied insects.

Pathogens: Using microbial agents such as Bacillus thuringiensis (Bt), a bacterium that produces toxins fatal to certain insects, provides a biological method of pest control. This is an excellent alternative to pesticides because it’s a similar approach of spraying plants but instead of spraying chemicals, you’re spraying probiotics.

Physical Methods

Barriers and Traps: Physical barriers such as screens, row covers, and mulches can prevent pests from accessing plants. Traps, including pheromone traps and sticky traps, can be used to monitor pest numbers.

Mechanical Removal: Manually removing pests from plants, whether by hand-picking or using water sprays, is another effective physical control method to knock populations down.

Chemical Methods

Last Resort: Chemicals should be used only when other methods are insufficient to keep pest populations below damaging levels. Selective and targeted application of pesticides can minimise environmental impact, and should be prioritised over “broad spectrum” chemicals which kill a wider range of biota.

The choice of chemicals should consider their effectiveness, persistence, and non-target effects, using the least harmful option first 

Regulatory Methods

Biosecurity Laws: Compliance with biosecurity regulations helps prevent the introduction and spread of invasive pests and diseases. Quarantine measures, import restrictions, and inspection protocols are essential components of regulatory control.

Reporting and Monitoring: Regular monitoring and reporting of pest occurrences help authorities manage and respond quickly to pest outbreaks, thereby reducing the need for widespread chemical interventions.

Daniel’s Wrap

The debate surrounding the use of pesticides and chemical controls in horticulture, especially within the urban landscape, is nuanced and complex. While these substances offer significant benefits in terms of effective pest control, increased productivity, and cost-efficiency, they also come with considerable environmental and health risks.

Employing an integrated pest management approach that incorporates genetic, biological, and cultural practices before reaching for chemicals can help mitigate some of these risks while maximising the benefits. Landscape designers and maintenance crews must weigh these factors carefully to make informed decisions that promote both plant health and ecological sustainability.

Ask yourself: do I want to create a landscape which is based in pro-life principles, or do I want to create a landscape which is based in anti-life principles?

Even if you fundamentally decide to go with a pro-life philosophy, you can still incorporate thoughtful chemical usage where appropriate, similar to how we use antibiotics for human health only when it’s necessary while understanding the damage it will do to our own micro-biome.

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