Low Chemical Gardening Choices
When trying to address problems with garden pests, weeds and diseases in the garden there are low chemical gardening choices which don’t require the use of chemical products. We have assembled a range of them below.
Pests – Insects, Snails and Slugs
There are many options available to reduce pest numbers apart from using manufactured chemicals that have various risks associated with them. Here are a number of better WiseGardening choices.
Sticky Insect Traps
Commercial ones are available, but you can make your own following instruction/s on many websites. Hang in locations with problem pests and monitor or replace when necessary. However, some of these may trap beneficial insects.
Snail/Slug (Gastropod) Traps
For snails/slugs, place cardboard/wooden/plastic board or flowerpot on ground in damp spot in garden. After 1 or 2 days lift and remove snails/slugs congregated underneath.
For slaters and earwigs as well as snails ad slugs make a container with holes near the top. Place it so that the bottom of holes is level with the ground – cover to keep rain out. Add beer or sweet liquid and vegetable oil to drown pests. Clear out trap regularly.
Plug in to 240v power point to attract and then electrocute insects. Locate these away from food preparation/cooking areas. Please note that the environmental impacts of these are not clear. Although they do not involve spraying chemicals, they may kill beneficial insects and they may use carbon-emitting electricity.
Provide Habitat for Predators
Increase Plant Diversity
Grow a large variety of plant species, herbs and ornamentals, especially those with brightly coloured flowers and those that are umbrella-shaped. This will create an ecosystem of interdependent species which keep each other in balance.
These can be home-made and are also available commercially.
These can be for birds or bats which use insects as food.
If you build a frog pond, the frogs will come and they are voracious insect eaters.
Lizard Sun-bathing Rocks
Smooth rocks in the sun attract lizards which eat insects.
Bag fruit individually or in clusters on trees to exclude pests.
Mounded around the plants you want to protect, wood ash can be an effective barrier. Create a thick layer around plant for protection. Replace when damp or depleted. But make sure that the ash was a result of an essential wood burning activity, otherwise it could be the result of an unnecessary carbon-polluting activity.
Use 5mm x 5mm (or smaller) netting pulled taut over a frame/structure around the plant.
Wrap a corrugated cardboard collar around base/trunk of tree/plant and secure with tape or string. Replace periodically over pest breeding season.
Put wobbly wire around plants you wish to protect from possums.
Corrugated Iron on Paths
This deters deer which don’t like walking on surfaces that are unstable and make noise when trodden on. Try to use old recycled iron.
Repellents and Attractants
This approach aims to use nature to attract, repel, enhance plant health and flavour. For example, planting Winter Cress Barbarea verna effectively attracts beneficial insects and entices the cabbage white butterfly to lay its eggs on the leaves. But the plant kills emerging caterpillars as they try eating it. Marigolds deter the cabbage white butterfly from laying eggs on brassicas as well as repelling root nematodes.
Decoy plants may be planted earlier than the main crop to entice insects. They can then be removed and the main crop planted. They can also be planted around the outside of a crop as insects usually start from the outside.
Artificial cabbage white butterflies can deter live ones for some time. They should be moved regularly.
Visual Bird Deterrents
Try hanging moving or reflective materials in trees such as lights, mirrors, reflectors, reflective tape, flags, rags, streamers, lasers, dog/human/scarecrow/large hawk models. These will need to be replaced or alternated since birds quickly become used to them and will resume normal activities such as eating fruit.
Better WiseGardening choices include methods that have subsidiary benefits such as requiring you to do some physical activity, such as those below, which are great for your health.
Removal by Hand
Look for pests and use your fingers to squash or remove them.
For snails and slugs pick them up and put in a bucket of water containing soap or detergent. This kills any eggs inside the snails and they can later be composted.
Water Jet or Hose
Hose pests off affected plants – e.g. Aphids can be easily removed and will not return.
Use swat to squash insect against a hard surface.
If it is possible, remove the heavily infested section of the plant.
Allowing ducks, chicken or geese to browse in areas of the garden infested with pests can help control their numbers. Such birds are effective predators of snails, slugs, insects and spiders.
Introduce Predatory Insects or Parasites
It is possible to purchase insects and other organisms which will attack pest insects in your garden from a number of suppliers.
There are many options available to reduce plant diseases in your garden apart from using manufactured chemicals that have various risks associated with them. Here are a number of better WiseGardening choices.
Avoid Using Seed Which might be Diseased
Use either certified disease-free seed or, if saving seed from your garden, make sure that the plant you are taking it from is healthy.
Don’t grow plants of the same family in the same bed for at least 3 seasons to avoid a build up of pathogens in the soil.
Bacteria survive in infected plant debris/litter, seeds and in soils. They are spread by contact, rain splash, vectors and infected seeds. Before and after harvest, dispose of infected plants/plant parts in sealed plastic bags in bins – do not compost them.
Disinfect gardening equipment (bleach/methylated spirits).
Avoid Moisture on Leaves, Especially at Night
Moisture persisting on leaves allows fungal spores to germinate. Use drip irrigation rather than sprayers or employ overhead watering early in the morning so that moisture will evaporate.
Prevent pathogens from entering the landscape by only purchasing healthy, vigorous, undiseased plant material. Refuse to purchase any plants showing any sign of disease or poor health.
Completely remove any plants that are either heavily infested with untreatable diseases (remove as much of the plant & root system as possible as well as much infested soil as possible).
Fungus and other pathogens in the top layers of soil can be destroyed by covering the soil with thin, clear or black plastic film and leaving in place for a number of weeks in the summer/hottest months before planting crops. Try to use recycled plastic to avoid the extra pollution of plastic production.
Plants cannot be cured of viral infections, so prevention is required.
Cleaning of tools (especially cutting tools) with bleach or alcohol between uses and between plants will help prevent transmission of virus.
Some pest insects e.g. aphids can transmit viruses , so control of these pests can reduce the chance of viral infection of plants.
Removal and Destruction of Infected Plants
Place infected plants in plastic bags, seal firmly and dispose of in rubbish bins or burn them.
Since viruses can only grow in living organisms for which they are specific, transmission to subsequent plantings can be minimised by practising crop rotation.
Use Virus-Resistant Varieties
There are many options available to reduce weed infestations in your garden apart from using manufactured chemicals that have various risks associated with them. Here are a number of better choices.
Cover soil/garden bed with black or clear plastic film. Leave plastic in place for several weeks during the hottest time of the year. This effectively ‘cooks’ the plants and seeds in the soil underneath. This can also reduce soil-borne pathogens. Try to use recycled plastic to avoid the extra pollution of plastic production.
Apply water heated to close to boiling point or beyond boiling in some commercially available saturated steam weeding devices to create steam. When applied to a plant it causes the plant cells to rupture then wilt and die. This treatment needs to be repeated on weed infestations in order to be effective. Note that heating water to produce steam also requires use of carbon-polluting electricity unless derived from renewable sources.
Apply boiling/close to boiling point water to a plant. This method causes plant cell rupture, followed by plant death. This treatment needs to be repeated on weed infestations in order to be effective. Note that boiling water requires use of carbon-polluting electricity unless derived from renewable sources.
Apply a direct flame using a fuel powered flame burner to a plant. The flame passes over the plant, increasing the temperature of the moisture in the plant causing cell rupture, followed by plant death. This treatment needs to be repeated on weed infestations in order to be effective. Note that this uses carbon-polluting fuel.
Cover with overlapping layers of thick cardboard, ensuring no light can penetrate to the soil. Then covered with a thick layer of organic mulch e.g. wood chips or bark.
Know Your Weeds
Identify the problem plant in order to ensure the treatment is targeted and effective.
Limit Soil Cultivation
Use no-dig gardening methods.
Reduce the chance of weeds succeeding by using vigorously growing plants and plant close together to restrict light to soil and, therefore, chances of germination. These plants can out-compete the weeds.
Suppresses weeds by preventing light from reaching seeds. This prevents germination of seeds or causes the seed to use up reserves trying to reach surface. Organic and granular mulch has additional benefits of reducing evaporation from soil and capture of rainfall.
Control existing weeds around the garden regularly to reduce weed seed build up. Prevent weeds from being imported to your site/garden by choosing weed free plants from the nursery. Remove any weed seeds that might germinate in the top layer of the planting media. Keep tools and equipment clean.
Care with Fertilisation
Extra fertiliser can give weeds an advantage as many can grow quickly when there is ample nutrition available. Limit fertiliser use to only when necessary. Use soil testing if possible to determine nutrient needs.
Removal by Hand
Remove individual weeds by hand pulling or using hand tools is a useful technique in small gardens or for low numbers of weeds. It is highly selective and is most effective on annual weeds and weeds which do not regrow from underground parts – care must be taken to ensure the entire plant is removed. This method is cheap, free and has little to no impact on surrounding plants and animals.
Girdling or Ringbarking
For large or woody weeds too large for hand removal, girdling (ringbarking) is a suitable option. Cut several centimetres of bark from the circumference of the entire plant. This will cause the plant to die.
Mechanical Cultivation (tillage)
Using powered devices e.g. rotary hoe or tractor. This approach can have the disadvantage of requiring use of carbon-polluting fossil fuel unless the device is driven by human strength.
Most approaches listed below can be used to both remove algae and prevent their appearance.
Organisms which consume algae
Add tadpoles or water snails since they use algae as food.
Place a net over the pond to catch falling leaves.
Prevent run off from adjacent areas that have been fertilized. This could be achieved by
growing a hedge or dense row of leafy plant species close to the pond.
If the pond contains fish, reduce the amount of fish food which also supports algal growth.
Removing some fish will decrease the amount of their faeces which after decomposition provide nutrients for algal growth.
Add aquatic plants -these will take up nutrients required by algae and thus limit their growth. Up to 60% of the pond surface can be covered with plant foliage.
As barley straw decomposes it releases chemicals, possibly hydrogen peroxide, which slow algal growth. Use the actual straw (not commercial preparations derived from it). Tie in bundles with string or put in mesh bags placed, if possible, near a waterfall or aerator since it seems to work better if water is oxygenated, but it may take many weeks. Barley straw does not kill algae or other pond inhabitants.
While mechanical approaches to reducing algae are not chemical, they are not as sustainable as the above methods since they require considerable material and energy use in their manufacture and/or operation.
In still waters, low oxygen conditions upset the balance of chemical nutrients for pond life and favour algal growth. Aerators help prevent algal growth by increasing dissolved oxygen levels. Make sure to clean any aerator regularly.
A mechanical filter (or skimmer) draws water in and traps algae. Cleaning the filter to remove the algae should be done on a regular basis.
Devices are available to shine UV light which kills algae without harming other pond inhabitants – they may be separate or attached to a pump. However, not all algae are susceptible to UV light and it works better if water is moving.
Although labour-intensive, this is possibly the quickest way to remove algae is manually.
Removal could be done using gloved hands, some sort of brush such as a circular toilet bursh, or a dip net. Manual removal allows easy collection of algae which can be usefully added to the compost heap.