The problem of garden pest control is as old as agriculture itself, which started when humanity first cultivated plants for food more than ten thousand years ago.
Modern conventional pest control methods often use chemical controls as the first option, and usually ignore the real causes of pest problems. They rely on routine, scheduled pesticide applications. Spray this chemical at this time of the year, then rotate to a different chemical because pests develop resistance to chemicals…
There are far more strategic, intelligent and cost-effective ways to manage pests than wholesale chemical warfare without regard for the long-term consequences. The most common-sense scientific way to manage pests is by taking an ecological approach to the problem, since we are ultimately dealing with ecosystems filled with living organisms in complex relationships to each other.
Consider the fact that plants have been growing successfully on the planet for 460 million years before humans ever existed, despite the existence of pests – what does this tell us? Nature does have effective means of controlling pests and regulating pest populations, so there’s no need to reinvent the wheel.
Problems with Chemical Pest Controls
Are there any good reasons why home gardeners, gardening professionals and farmers shouldn’t use modern synthetic chemical pest controls? The main reasons are as follows:
- Chemical pest controls provide a temporary fix at best, and are ineffective over the long term.
- Chemical use disrupts the ecological balance. Predator insect species which eat pests and naturally control their numbers are more sensitive to pesticides. It has been consistently observed that after chemical pesticide use, there is a loss of predator species, and an explosion of pest population numbers.
- Pests naturally develop resistance to chemical pesticides as an evolutionary survival mechanism, so there’s a need to rotate pest control chemicals.
- Environmental toxicity is an undesirable consequence of pesticide use. Chemical persistence in the soil, bioaccumulation in living organisms, soil mobility and contamination of waterways and groundwater are known issues with chemical use. Local applications of chemical pesticides may move to off-site locations, contaminating food crops and harming non-target species.
- Toxicity to non-target species, including people, pets and wildlife.
- Social acceptance – increased awareness and public concern about chemicals.
- And the big one… Cost $$$ – which is ongoing! In 2016, the agrochemical market worldwide was worth 215.2 billion US dollars, and expected to increase to 308.9 billion US dollars in 2025!
It’s been said that necessity is the mother of invention, and to address the abovementioned issues, a far smarter approach to pest control has been developed, known as integrated pest management, abbreviated as IPM.
What Is Integrated Pest Management (IPM)?
IPM is a systematic, scientific pest management strategy based on prevention, monitoring, and control, that uses a combination of techniques to limit pest populations and the damage they cause to economically acceptable levels, while eliminating or drastically reducing the use of pesticides to minimise risks to people and the environment.
How Does IPM Work?
There are three key components to IPM strategy:
Let’s examine each in turn.
The goal of IPM is the long-term prevention of pests or their damage by managing the ecosystem.
IPM adopts a proactive approach – by understanding the environmental factors that affect the pest and its ability to thrive, we can create conditions that are unfavourable for the pest. This is the complete opposite of reactive nature of conventional chemical pest control, which is predicated on eliminating visible pests right now.
There are three parts to this IPM strategy, which are carried out as a series of consecutive steps in the following order:
- Monitoring – assessing the nature and scale of the problem by checking to identify pest types, pest numbers or pest damage.
- Correct pest identification – to determine whether the pest is a problem, and what the best management strategy is.
- Deciding to take action – After considering the pest biology and environmental factors, we can then decide if the pest be tolerated, or if the problem needs controlling, and if so, which management methods are the most effective.
Integrated Pest Management is integrated because it combines various pest management control methods together for greater effectiveness.
It’s only logical that if a certain pest control method is, for example, 60% effective, and another is 30% effective, then combining the two would increase the overall effectiveness of the pest control measures.
There are four categories of pest controls employed in IPM:
- Biological controls
- Cultural controls
- Mechanical and physical controls
- Chemical controls
Various types of controls (i.e. biological and cultural controls), or methods from within those controls (i.e. several different mechanical/physical controls), can be deployed together, and they can be escalated in terms of risk if required.
IPM Strategy, Escalation and Integrated Solutions
The pest control strategy of modern agriculture is to utilise the most toxic chemicals as the first option. That’s not very strategic because if pests become resistant, that leaves no escalation options available. In IPM, we would begin with the least toxic chemical control (or a non-chemical control) that would get the job done, leaving the most toxic chemicals as a last resort instead!
What happens when modern agriculture uses restricted chemicals so toxic that they’re not legally available to the general public for pest control? The contamination of food and water with pesticide residues is well documented, as is their impact on the environmental ecosystems which keep us alive. Paying such a heavy price for the temporary and short-term control of pests is a perfect example of a Pyrrhic victory, where the losses negates any real sense of achievement, in other words, an empty victory, which isn’t very strategic at all.
IPM is a scientific, evidence-based approach to pest control, which is based on the following principles.
- Strategy – using a systematic calculated escalation strategy is a more efficient and cost effective way to control pests. The least harmful controls (chemical or other) are employed first, and usually combined to increase effectiveness. If these controls prove to be ineffective, then a step-wise escalation can be employed, using controls with slightly more environmental impact to get the job done. This leaves the control methods with the most environmental impact as a last resort option only.
- Prevention, monitoring, and control – pest control solutions are developed based on pest biology and behaviour.The science exists to describe and understand pest life cycles, habits and preferences, and we can use this knowledge to implement more effective pest control solutions by targeting pest vulnerabilities.
- Combination of techniques – the cumulative effectiveness of controls provides greater levels of pest controls. By combining a pest control which is for example 60% effective with another which is 30% effective, we can achieve a solution which is 90% effective, and this is far more effective than any solution employed on its own.
- Limiting pest populations and damage to acceptable levels – setting realistic pest control goals preserve natural controls, and are much more achievable. Eliminating a pest species is not practical, in fact it’s quite impossible, as nearly a century of industrial agricultural chemical usage has proven, which is why we still have pests. The goal is not to eliminate every pest, it’s to preserve a crop. If pest populations are reduced to the point where the damage is not significant, and natural pest predator insects are kept alive to reduce pest populations naturally, then the goal can be considered achieved.
- Eliminating or significantly reducing the use of pesticides – reducing chemical use minimises cost as well as risks to people, non-target specie and the environment.
There are many control methods available to use in formulating IPM solutions, and in the next section we will examine each in detail.
Mechanical and Physical Controls
These controls block pests out, make the environment unsuitable for them, or kill them directly.
Physical controls include:
- Manual methods – hand removal of small pest infestations, disease infected or pest infested leaves, or hosing pests off.
- Barriers – netting, fencing, electric fencing, tree banding, fence spikes, root barriers, mulches for weed control, sprays which create pest barrier.
- Traps – tree glue banding, tree cardboard banding, pheromone traps, sticky traps, newspaper traps, snail traps.
- Heat based – boiling water or flaming weeds, soil steam sterilization for diseases.
Mechanical controls include:
- Mechanical traps, such as rodent traps (lethal and non-lethal) and possum cage traps.
An Example of Physical Control – Calcined Kaolin
Calcined Kaolin, sold as Surround WP in the agricultural sector, and under various other names in the consumer gardening industry, is a form of clay, and is certified for use in organic gardening. It forms a white film over stems and leaves, reflecting the sun’s rays to prevent fruit sunburn, which is it’s traditional agricultural use.
This natural substance also acts as a barrier to pests, and has been used for this purpose by European organic farmers for quite a while now. The layer of calcined kaolin makes it hard for insects to walk on and presents an unnatural surface for them to interact with, causing irritation, confusion and an obstacle to feeding and egg-laying. It may also create a barrier which prevents fungal spores establishing on leaves.
Calcined kaolin is sprayed on leaves, stems and and fruit – avoid spraying on flowers, as they don’t function to well with a layer of clay over them! It’s effective in control of:
- Gall Wasp
- Codling Moth and Oriental Fruit Moth
- Powdery Mildew
- Stink Bugs
For control of gall wasp, spray on new green shoots and branches which the pests lay their eggs into, they can’t attack branches when they have hardened off and become woody. Can be combined with a scent-based yellow sticky gall wasp trap for more effective pest control levels.
For control of codling moth, spray young fruit and respray to keep them covered. Can be combined with a pheromone-based sticky traps, insect exclusion netting bags and underplantings of nasturtiums for more effective pest control levels.
These controls are practices which disrupt the environment of the pest, reducing pest establishment, reproduction, dispersal, and survival. Many of these methods work by improving soil and plant health, remember that plants and soil ecology can naturally control pests and diseases!
Cultural controls include:
- Changing irrigation and fertilisation practices
- Crop rotation
- Selecting pest-resistant plant varieties
- Sanitation and hygiene – removing infected plant material and fallen fruit
- Eliminating debris where pests can hide, or locating wood piles and other materials away from crops
- Removing weeds which are hosts to pests
- Companion planting – pest repellent and beneficial insect attracting plants
An Example of Cultural Controls – Citrus Leaf Miner
Citrus leafminer moths only attack new growth flushes in summer and autumn. Once leaves harden off, pest can’t mine into them.
To control citrus leaf miner:
- Fertilise citrus in late winter to promote strong growth in spring, when citrus leafminer is absent or in extremely low numbers.
- Peak pest periods occur in late summer and autumn, so to reduce new growth during these times, avoid over-fertilizing, using high nitrogen fertilizers or overwatering in summer and autumn. Use just enough fertilizer and water to support normal growth, but no more than that.
- Spraying horticultural oil on new growth flushes of leaves deters citrus leafminer from laying their eggs, as they avoid surfaces sprayed with oil. Begin spraying new summer growth as soon as it emerges, before the leaves reach 10 mm (3/8”) in length.
Biological control agents, the natural enemies of pests, can be use to keep their populations in check.
A wide variety of organisms are used for biological control of pests:
- Predatory mites
- Parasitic wasps
Listed below are the various categories of biological controls organisms used commercially and the pests that they control.
Please note this is not an exhaustive list, and some of these biological controls may not be available in every country.
Biological Controls – Ladybirds and Lacewings
Biological controls include:
- Spotted ladybirds (Harmonia octomaculata and Harmonia conformis) for control of aphids
- Ladybird (Cryptolaemus montrouzieri) for control of mealybugs and soft scale insects.
- Ladybird (Chilocorus circumdatus) for control of armoured scale insects.
- Green lacewing (Mallada signata), generalist predators, for control of wide range of pests including aphids, scale insects, mealybugs, caterpillars, whitefly and mites.
Biological Controls – Predatory Mites
Biological controls include:
- Persimilis predatory mite (Phytoseiulus persimilis) for control of spider mites.
- Montdorensis predatory mite (Typhlodromips montdorensis) for control of thrips, whitefly, other small insects and mites.
- Californicus predatory mite (Neoseiulus californicus) for the control of spider mites, broad mite and cyclamen mite.
Biological Controls – Parasitic Wasps
Biological controls include:
- Aphytis parasitic wasp (Aphytis lingnanensis), parasite for control of red scale and other armoured scale insects
- Encarsia Parasitic wasp (Encarsia formosa), parasite for control of greenhouse whitefly and tobacco whitefly.
- Eretmocerus parasitic wasp (Eretmocerus hayati), parasite for control of silverleaf whitefly.
Biological Controls – Parasitic Wasps
Biological controls include:
- Parasitic wasp (Trichogramma carverae), moth egg parasite for control of codling moth, oriental fruit moth, light brown apple moth and other pest caterpillars.
- Parasitic wasp (Trichogramma pretiosum), moth egg parasite for control of heliothis and other pest caterpillars.
Biological Controls – Nematodes
Biological controls include:
- Entomopathogenic nematode (Heterorhabditis zealandica) for control of scarab beetle, including lawn beetle grubs, and weevil control.
- Entomopathogenic nematode (Steinernema feltiae) for control of fungus gnats in indoor plants, nurseries, mushroom growing and hydroponic systems.
Biological Controls – Bacteria
Biological controls include:
- Milky Spore (Paenibacillus popilliae) is a bacterial biological control primarily for Japanese beetle grubs.
- BT (Bacillus thuringiensis subsp. Kurstaki) sold as DiPel and (Bacillus thuringiensis subsp. Aizawai) sold as XenTari are bacterial biological controls for caterpillars .
For Australian readers, at the time of writing, the following companies were operating as suppliers of biological controls:
- Ecogrow – http://ecogrow.com.au
- Nemassist – http://www.nemassist.com.au
- Biological Services – http://www.biologicalservices.com.au
- Bugs for Bugs – https://bugsforbugs.com.au/
Chemical control is defined as the use of pesticides to control pests. In IPM, chemical controls are used only when needed, and usually as a last resort, combined with other methods for more effective, long-term control.
How are chemical controls used in IPM?
- The most selective and least toxic pesticides that will do the job are preferred, leaving possibility of escalating to stronger pesticides.
- They are used in ways that are safest for environment and people, such as spot spraying, minimising wind drift and runoff, avoiding spraying before rain, spraying in evening to protect bees.
Selective pesticides (ones which only target certain pest species) are preferred to broad-spectrum pesticides which kill all insects, including the beneficial ones.
Chemical controls include relatively safe products accepted in organic agriculture such as:
- Natural horticultural oils – these work as suffocating agents, blocking the insects breathing pores, so these only work by direct contact, they only work if the pest is sprayed.
- Neem oil based pesticides – work in two ways, as an anti-feedant which stops the insect feeding, causing it to starve after approximately three days, and as a life-cycle disruptor, which stopes the insect developing to an adult stage and breeding, preventing the next generation of pests.
- Pyrethrum pesticides – are non-specific insecticides and kill most insects, they remain effective for a short period, as they only have a 24 hour persistence, and are broken down and deactivated when exposed to sunlight. Pyrethrum is only organic certified when it does not contain synthetic synergists, such as piperonyl butoxide which is not organic certified!
- Copper fungicides – such as copper hydroxide, copper oxychloride
- Sulphur fungicides – such as wettable sulphur and lime sulphur
- Potassium bicarbonate fungicides – note that these require a wetting agent such as horticultural oil to make them stick
- Plant oil based herbicides – are made of geranium or pine oils, and work by stripping off the protective wax layer of leaves, causing weeds to dry out the next day, these burn leaves only which make them very effective on annuals but don’t kill the roots of perennial weeds. Repeated use will deplete the energy reserves in roots and eventually eliminate them.
- Vinegar based herbicides – use highly concentrated vinegar, and also work by stripping off the protective wax layer of leaves, but most contain common salt (sodium chloride) which is bad for the soil!
Creating an IPM Program
There are 6 major components common to all IPM programs:
1. Monitoring – use of regular site inspections and trapping to determine pest types, numbers and damage.
2. Action Levels – set thresholds for when management action is needed, as pests are almost never eliminated completely.
3. Prevention – incorporate preventive measures (cultural controls) into existing structures and designs for new structures.
4. Pest identification – keep records to identify patterns and trends in pest outbreaks, and which pests are the problem.
5. Controls – use combinations of physical-mechanical, cultural, biological and chemical controls (last resort, least toxic first) to reduce pest problems.
6. Evaluation – assess and review effectiveness of pest management strategies.
The Ecological Approach to IPM Strategy
To manage a pest, it must be understood in terms of biology and ecology. Here is a series of steps to systematically develop ecologically sound pest management solutions:
- Identify the pest as accurately as possible.
- Learn about the pest’s habits, life cycle, needs and dislikes.
- Try to exclude the pest from the area, if possible by making it inhospitable to its survival or reproduction.
- Try to remove food, water and shelter which the pest uses.
- Locate the pest’s home and determine the travel patterns.
- Identify all possible control options available before taking action.
This approach will work for any type of pest, whether it’s a larger animal such as possums or fruit bats, an insect in the garden, or even an indoor pest.
By utilising an integrated pest management strategy, we can realistically control pest levels much more efficiently and cost-effectively, while minimising unnecessary harm to non-target species and the environment. Working smarter, using science and systematic strategy, is a much better approach to pest control than irresponsibly reaching for the most toxic chemicals available, who could dispute that?