Nature is a friend and not an enemy and we should aim to work together.
Probably the most important lesson we have to learn is that trying to fight nature is foolish and to co-operate is common sense. When we co-operate, Nature helps to solve the problems, and the way forward can become clearer to us. If we observe Nature closely we are more inclined to find the answers.
Garden pests and their natural enemies co-exist in balanced populations in well managed, organic and permaculture gardens. All one is required to do, really, is let them get on with life and there won’t be a problem of losing all the crop to invaders.
In the days before pesticides were used in such abundance, as they are today, crop losses were generally only 3.5%, whereas now it is an estimated 25%, despite being sprayed with chemical pesticides.
The truth of the matter is that progress has not been made in the war against insects as they develop immunity against the pesticides, plus their natural predators and parasites are being destroyed along with them…. So, spraying each bug you see in your vegetable garden with poison backfires on you. In a very short period of time the same kind of bug is back again, but now there is more of them.
The natural enemies of your ‘pests’ do not usually reappear as quickly as the pests (slower reproductive rates) and some insecticides are more toxic to predators and parasites than others, and in the meantime resistance to the poison is developed.
Individual insects have different levels of resistance to the sprays and every time you spray an insect population you change the balance between susceptible and resistant individuals. The resistant individuals survive and reproduce and the beneficials are more prone to dying.
So it stands to reason that the more pesticides you spray with, the faster you lose your crop.
What are natural enemies of your ‘pests’?
There are basically three types of natural enemies:
- Predators that eat insects: These include spiders, ladybirds, wasps, praying mantis, lacewings and dragonflies. Each predator can eat hundreds, even thousands of insects in a lifetime and some of them, like spiders, eat a wide variety of them. Money spiders (Linyphiidae), with their voracious appetites, can devour thousands of aphids. Aphids have little nutritional value, so spiders need to eat other insects also, in order to have a balanced diet. Predator insects and arachnids do not damage crops.
Most of these are insects that lay eggs inside the body of a living insect called a host. The parasite feeds on its host until it finally kills it. Then the adult parasite emerges from the dead host and searches for more insects to lay its eggs in. Using parasites is a slower way to kill pests but it is very effective. There are many examples of insect parasites in an unsprayed garden, and if you take time you should find some.
- Diseases carried by viruses and fungi can infect and kill Insects: Due to the fact that diseases are carried among the insect pests in your garden, whole populations can be wiped out quickly.
The cabbage white butterfly (Pieris brassicae) is a common sight in the vegetable garden and illustrates a number of examples of biological control in action. This species was accidentally introduced from Europe and has become a significant pest. Its green, black and yellow larvae cause a lot of damage to the mustard family (Cruciferae) and particularly to cabbage, broccoli, cauliflower and rocket and also to nasturtiums.
This butterfly tolerates both hot and cold weather and seems unperturbed by the wind and breeds continually throughout the year, laying up to 125 eggs at a time. Populations surge even more in the cold months. Consequently it has the potential to be a serious threat.
However Mother Nature has stepped in with a few nifty solutions for its extermination, or at least to keep the population in check. When left alone Nature always strives and brings about a balance but when we interfere with pesticides we upset the balance:
- Argentine ants: Which are also aggressive aliens, have been observed carrying away the first newly hatched larvae to curb population growth.
- Tachinid fly larvae: Two species have been recorded as parasitizing the Cabbage White caterpillars. The adults look like small hairy houseflies and survive on the nectar of the flowers but the larvae live as parasites on other insects. They do this in one of two ways. Small, white oval eggs are laid on the outside of a caterpillar. The eggs hatch into tiny maggots which bore into the living victims and devour them. First the body juices, then the fat and eventually the vital organs. The victim has to succumb and eventually only one brawny hairy adult Tachinid emerges. Other Tachinids lay lots of tiny eggs on the surface of food plants and these are swallowed by grazing caterpillars. The emerging maggots bore through the gut wall and proceed to feed, leaving the victim’s vitals to the end. In order to get the air they require they pierce the body wall of the host and send their own breathing tubes to the surface or connect directly to the respiratory apparatus of the caterpillar.
- Parasitic wasps (pteromalus purparun):
The female wasp lays her eggs in the body of the final larvae stage of the caterpillars and then her grubs feast on the tissues of the host. They follow the same pattern of consumption as the Tchaninid maggots and it would be unwise to kill the host before the grubs are fully developed, as they attack the nervous system last of all. The caterpillar remains alive and fresh until just before the wasp grubs are ready to pupate and then they start nibbling at the brain. This brings about changes in the caterpillar’s behaviour and it leaves the food plant and migrates up any vertical surface in the vicinity in a premature attempt to pupate. The wasp grubs finally kill the ailing caterpillar and emerge to spin tiny cocoons covered in a golden net which will protect the pupating wasp larvae from attack by other parasites. Clusters of these cocoons can often be seen on vertical structures in and around the garden which has not been sprayed. Unfortunately these wasps are not that active during the colder months when the Cabbage White butterfly tends to have the upper hand.
Re-establishing the Natural Order:
When you have left your garden and the insects to their own devices and you still get too many pests and diseases then there are some important other factors to take into consideration and rectify. It is never necessary to resort to chemical poisons.
Soil is the Foundation of All Growing Things. A healthy soil produces healthy plants and healthy plants resist attack from pests and diseases. You need to re-instate your soil fertility and establish the natural order, therefore soil-disturbance should be minimized.
Ploughing and digging disturb the balance among soil insects, fungi, viruses, bacteria and other soil life. They break up the root channels and soil structural units (aggregates) so that the soil is not able to perform its intended function. These disturbances cause rapid loss of organic matter upon which the crop and soil organisms feed.
Use organic matter and manure in place of chemical fertilizers.
To improve your soil, dig less, mulch more and compost always.
By growing leguminous crops your soil fertility and organic matter content can be greatly improved. They of course also produce edible leaves and seeds.
This conserves soil moisture and keeps the surface cool in hot summer days and also protects against erosion. The combination of digging less or not at all, applying compost and mulching will cause your soil to flourish beyond your expectations.
- Diversity: You also need to provide habitats for predators. Suitable, natural habitats and protection from existing ones are required and diversity of plants will be valuable in this process. Windbreaks are also required and these all help to re-establish the natural order for predator balance. Re-introducing plant diversity is critical, as diversity is nature’s most effective way of maintaining the pest/predator balance and of ensuring continued soil fertility. Rotations and intercropping and mixed cropping are essential to re-establishing the natural order.
The way you water your garden is of great importance in maintaining healthy plants — i.e. those that repel insect attack. Deep watering is essential — not just a daily sprinkling. In fact you should not have to water your plants every day, even in the heat of summer, unless they are tiny seedlings that are still getting a grip on things. Shallow watering causes the roots to turn upwards to get to the water. You can estimate the depth of your plants roots by the height of the plant. As above so below. So with deep watering and mulching you should at most only water every third day.
Plants and Herbs for Pest and Disease Control
Some references are taken from Natural pest and Disease Control by Henry Elwell and Anita Maas.
If your soil, mulching and watering is in place and you still have pests or diseases then there are ways you can combat this but first assess if this is necessary and if you leave well enough alone it will not rectify itself.
Here are some remedies for the more common pests or insects.
The small black ants which encourage aphids are those which most interest the gardener or farmer. They are attracted to the honeydew produced by the aphid and they transport young aphids from one location to another thereby spreading diseases carried by the aphids. The ants also scare away predators but many species of ants assist the gardener by killing off insect pests such as cutworm, stalk borer, spider mites, termites and others. So it is advisable not to indiscriminatingly go about destroying them.
Their Life Cycle: Ants are small insects which nest underground, usually making use of existing cavities under rocks and among roots. A colony consists of a king and a queen and a large number of workers. The queen lays clusters of small white eggs which are then moved to a safe place by the workers. In addition to feeding on the honeydew secreted by the aphids and scale insects, ants feed on a wide variety of other insects, many of which are potential pests.
Ants release chemicals which enable them to recognise companions from the same colony to raise the alarm or to sting enemies.
Strong smelling plants like khaki weed, herbs or tomatoes act as deterrents when grown amongst plants.
The tomato (Lycopersicon esculentum) is a wonderful insecticidal repellent as well as being bactericidal and fungicidal and prevents egg laying.
Wood ash is effective but ash from specific vegetation is more effective against specific insects. The ash from the Acacia tree is very effective against numerous insects and ants.
Some household ants can also effectively be repelled by sprinkling baby powder and lime.
The small black garden ants which harvest the aphid have been found to be most effectively deterred by a spray made from black jacks’ seeds or Khaki weed. Spray made from rhubarb leaves or tomato leaves will exterminate the ants.
Host Plants: Most plants, shrubs and trees and particularly the tender young shoots.
As aphids are sap feeders they cause a lot of damage in large numbers and can remove sufficient sap to kill off leaves and the growing tips. They are very important vectors of plant viruses and the honeydew they produce attracts a large number of other pests like ants and fruit flies.
Lifecycle: Young aphids are produced directly from the mother without the egg stage. There are no males in the warmer areas of the world. These insects usually are wingless but will produce wings and fly to other plants when the host plant becomes overcrowded. Flying aphids can be carried long distances with the wind. Young aphids are said to be spread by the ants feeding on the honeydew.
Hoverfly larvae and ladybirds eat up to 250 aphids a day and other predators are lacewing larvae, parasitic wasps, praying mantis and small birds like the Cape Witogie – little white eye (Zosterpidae).
Identification: Adult aphids are only a few millimetres long. They are round and plump and the colour of each species is different, varying from yellow, green, brown, grey, white and black. The woolly aphid looks like a small piece of cotton wool. All species tend to cluster close together on the tender parts of the plant. They are soft-bodied and can be squashed easily with the fingers. Aphids form wings only when they are overcrowded and need to migrate.
Recommended Remedies: By growing healthy plants and using compost in preference to manure the plants develop their own inbuilt resistance to aphid attacks.
Manures and artificial fertilizers, particularly nitrates, produce sappy fleshy plant tissue that are attractive to the aphids.
Plant diversity can successfully control aphids as well.
Growing Garlic, chives, marigold, nasturtiums, parsley onions and other pungent herbs as companion plants also repel certain species of aphid, particularly greenfly.
Nasturtiums grown as companion plants are recommended for repelling woolly aphids or as a spray to kill them and pigeon pea is said to repel green and grey aphids.
Milkweed, thistle and black nightshade are good trap or decoy plants to attract aphids away from the main crop.
Diamond-back Moth (Plutella xylostella):
When the moth is resting a pattern of three diamonds can be seen along the line where the wings meet over the back.
This moth is detrimental to all Brassicas, which are cabbage, cauliflower, broccoli and Brussels sprouts.
The small greenish caterpillars are about 8mm long and they eat numerous holes into the plant leaves, which seriously affects the vigour of the plant. They are particularly active in the dry season. These small green caterpillars can be seen on the underside of the leaves, lying in a protective web. The ash-grey female moth lays her tiny yellowish-green eggs either singly or in small groups on the upper surface of the leaves. They hatch in a few days into small green caterpillars which move to the underside of the leaves to feed. They grow rapidly, attaining full growth in about 10 – 30 days, depending on the temperature.
The 12mm long caterpillars spin silk cocoons under the leaves in which they pupate. The adult moth emerges about one week later.
They can multiply rapidly if the conditions are favourable as the female lays about 50 eggs at a time.
Recommended Remedies: Summer rains and frequent irrigation reduce the mating of the moths and wash off young caterpillars and the pupae, but it is necessary to direct strong sprays of water to the underside of the leaves.
As this is not always a successful method it is necessary to make some herbal repellent sprays too.
Sprays made out of African marigold, black jacks or khaki weeds, chilli, garlic, tomato and basil can be very effective. Adding a teaspoon of cooking oil to the spray helps it adhere to the leaves for a longer duration.
Make sure to thoroughly spray the underside of the leaves to clear the pupae.
Bean Fly (Ophiomyia Phaseoli):
Bean flies and their maggots attack various species of beans of and also other leguminous plants. The young plants can be seen wilting and dying off and investigation will reveal decayed and hollow stems at ground level with a small maggot inside. The leaves of the plants may show yellow spots where the adult fly has laid her eggs. On mature plants the grub may be located higher up on the stem.
Life cycle: The female is a tiny black fly which pierces holes in the leaves of plants and lays eggs inside the tissues. The eggs hatch in 2 – 4 days and the maggots eat their way down the stem to just above the ground level. There they complete their development and then the grown maggots pupate and become adult flies in about 20 days.
The greatest damage is caused from November to January inclusive. From February onwards a parasitic wasp called Opius liogaster helps to suppress the pest.
The best way to identify the insect causing the damage is through the type of damage as mentioned above. Early warning of this pest can be noticed by the presence of yellow blotches on the leaves, which form around small punctures made by the fly when it laid its eggs.
Recommended Remedies: Prevention is better than cure and companion planting or routine spraying with aromatic herbs is the first approach to this problem. Remedy against the maggots and pupae is the first option because the maggots burrow into the plant material but as soon as they have hatched it is not possible to treat it directly. However future numbers of the fly can be reduced by removing the infected leaves where the eggs have been laid.
Herbal repellents for the fly stage can be made from garlic, tomato leaves and marigolds.
However there are also fly stage predators and by encouraging birds in your garden the fly numbers can be drastically reduced. Free range chickens, especially bantams, also will contribute.
To rid the plants of eggs you can sprinkle wood ash around and dust the leaves of the plants as well.
Cutworms attack young seedlings and this greyish caterpillar emerges from the soil at night, encircles the plant with its body and cuts through the stem of young plants just above the ground level, leaving the wilting top to die. They are general feeders and will attack almost any kind of plant and a single caterpillar may cut down several seedlings in one night.
They are identifiable where a young seedling is lying severed just above the ground. A small hole may be found in the soil near the severed plant, which when excavated will reveal the curled up smooth greasy-grey caterpillar.
Life cycle: They emerge in spring and a single female may lay 600 – 800 eggs which hatch approximately thirteen days later into tiny black caterpillars. The young initially feed on plant leaves for 10 days before burrowing into the soil where they then live during the day, lying in a curled up position about 25 cm to 30 cm below the surface, to emerge at night to feed.
The fully grown 30mm long caterpillar burrows about 25mm and turns into a smooth reddish-brown pupa. It remains in the soil for 2 – 3 weeks before emerging as a moth.
Recommended Remedies: One of the simplest and most effective control measures is to concentrate the hens or Bantams on to the beds before planting as they will scratch the soil and eat the worms.
Mulching also deters the moths from laying eggs and liming acid soil is also a deterrent.
The squashed ripe fruit of the Sodom apple steeped in water and then dug into the soil controls cutworm too.
For small infestations you can dig the cutworm out with a sharp stick and carefully search around the base of the damaged plant to find the small entrance hole to its hideout. Then dig along the tunnel to find the grub.
It is also recommended to water around the plants with a mixture of grated turnip that boiling water has been poured over and then cooled.
Nematodes attack a very wide range of plants and causes wilting and also poor growth of the leaves and fruit. Nematodes leave open wounds in the root tissue which encourages the occurrence of plant diseases, however they are essential to good soil structure as they break down organic matter into humus. Some nematodes are beneficial organisms as they keep each other in check and parasitize the larvae of many insects like, armyworm, beetles, bollworm and leaf miner.
Lifecycle: They live in the soil and are worm-like creatures which feed on soil bacteria, fungi, algae and some feed on the roots of plants. They are very small and burro into the root tissue of the plant where they mature and lay eggs, causing localized swelling on the roots. The young emerge from the eggs and move into the soil in search of another suitable plant. This life cycle is approximately 4 weeks.
As they cannot be seen with the naked eye, they can be identified by the damage they create.
Recommended Remedies: Nematodes are always in the soil but need to be in balanced, harmless numbers. The most permanent solution is to minimize soil disturbance and to ensure a high level of organic matter, lots of compost and mulch, as well as rotating crops.
Plants like khaki weed and marigolds are very good at keeping the damage from nematodes to the minimum.
Companion planting is also very beneficial in dealing with nematodes.
Fruit Fly (Tephritidae):
Fruit flies can be found in virtually every soft fruit, including apples, quinces and avocados.
The maggots of the fruit fly eat into the flesh of the fruit and promote rotting.
There are several species of fruit fly. The small fly can be recognized by its shiny eyes and striped wings. The body is light brown with darker markings: stripes or dots. It holds its wings at a wide angle to the body and appears to trail the back edge of them as it rests or walks. The maggots are small, legless and creamy white.
Life Cycles: In the summer the female cuts a hole in the skin of the fruit and inserts a number of eggs. The first sign of infestation is tiny brown punctures in the skin of the fruit from which clear gum exudes.
The eggs hatch in 2 to 4 days time and the maggots feed on the tissues of the fruit for about 2 weeks. During this period the fruit is likely to rot and drop to the ground.
At the end of this period the maggots are fully grown, approximately 10 mm long, and leave the fruit to burrow into the soil and pupate.
After 2 to 3 weeks the adult flies emerge and in winter the flies tend to congregate on the underside of leaves of certain trees like orange and loquat. The honeydew secreted by scale insects and aphids attract them.
The female fly also lays her eggs in the growing tips of the cabbage tree. The maggots tunnel down the branches keep just beneath the bark causing a slimy mess under the bark and die-back of the shoot.
Recommended Remedies: I have found spraying the fruit just when they start forming, and continuing to spray if it rains or after a period of about 4 weeks, keeps the fruit fly from laying its eggs on the fruit. This method is as effective as your spraying is. When your tree is full of new little fruits it is not easy to get to all the fruits and to spray them completely but the more efficient you are in this process the less you will have the fruit fly laying eggs in the fruit.
The spray that is most effective is made of strong smelling plants: rue, lavender, garlic and wormwood (Artemesia Afra) and khaki weed as well as Rambos (Pelargonium papilionaceum) are very effective.
An assortment of these plants with one or two lemons added into a bucket of water and left to stand for a day and night will make a very effective spray.
Another method that I have tried and found very effective is to drill a hole into the trunk of the fruit tree and drip some Balsem Kopiva in just when the fruit starts to form. The bitterness of the oil seeps into the tree and the fruit fly tends to steer clear.