Garden Pests - Prevention and Control

The Organic and Chemical options for Controlling Garden Pests.

The word ‘pest’ conjures up, for many people, a vision of hordes of aphids on roses or caterpillar on cabbages. The vision is quite justified because both are pests and both tend to infest on a worldwide scale. Agriculturists and horticulturists view any organism that interferes with crops as a pest—whether it be a virus or a predatory animal.

This article leaves aside the viruses fungi and bacteria and the animals like cottontail rabbits, deer and my own personal nemesis the grey heron, and concentrates on insects and insect-like pests, including also slugs and snails (molluscs) and eelworms (nematodes).

Insects are the largest group of creatures on earth. In evolutionary terms they are highly successful, and have proved to be man’s fiercest competitors. Historically, insects have caused more deaths to mankind than all wars put together.

Insects will attack most plants, whether they live in the garden, the house or the greenhouse. Like all illnesses and disor­ders, prevention is better than cure and the best way to reduce your losses is to ensure that your plants are healthy when planted and then well cared for.

Many physiological disorders of plants (caused, for instance, by too little water or too much nitrogen fertilizer) pave the way for attack by pests. So as soon as you notice any signs of distress or damage—act promptly.

Knowing what to look for

The pest itself may be almost invisible. Eelworms, for instance, are difficult to see under a +microscope. But their size bears no relation to the damage they can do. Even visible pests may not always be sitting in full view. You may have to dig underground and study the roots to determine the cause of the trouble, or wait for night to catch such creatures as slugs.

Pests which attack leaves and flowers are the most easily identified because the damage occurs rapidly and is usually quite recognizable. Two main groups of pests attack leaves: those which have biting mouthparts (for example beetles) and those with sucking mouthparts (such as greenfly). They may hide inside or outside the leaves or, like the notorious leaf-miner, burrow between the middle layers of leaf tissue.

Larger pests (like caterpillars) are usually more noticeable but they may attack and run (or fly) away, in which case you should spray, or lay bait, against the next visit.

Fortunately there are many methods of control at your fingertips, providing you diagnose the enemy correctly and act as swiftly as you can.

Understanding the enemy

Knowing something about the life cycles and habits of pests can help you in anticipating and preventing trouble. For instance a major factor in determining how active they are is temperature; the warmer it becomes the busier they get. And up to 35 C (95 F) they breed faster too. Cold winters greatly decrease the numbers overwintering in the garden.

Day length also plays a part in controlling the breeding seasons and migration patterns of many insects. This is why they always become scarce in autumn, even before cold weather arrives. Clear away and burn garden refuse every autumn because it provides ideal shelter for overwintering pests. Many overwinter as eggs which can also be destroyed by the use of insecticides.

Use of Chemical insecticides

Most pesticides are sold under trade names, partly because the chemical names and formulae are cumbersome and difficult to remember. You can, however, be sure of getting the right product by reading the contents on the label and checking with the chemical, or proper, name given here.

Always use protective clothing. Rub­ber gloves are important and be sure always to wash hands and face thor­oughly after using insecticides. Never allow children or animals to be with you when sprays are being applied, and don’t let them eat anything that has just been sprayed. Also wash out all spraying equipment after use—but not in the kitchen sink.

In some cases you may be able to use physical methods of combat such as picking caterpillars off plants and burn­ing them. These are always preferable to spraying, because all sprays have some adverse effect on the plant. This is why you must adhere strictly to the manufacturer’s recommended rate of application.

How insecticides work

Insecticides kill in two main ways; first as a stomach poison, when the pest either cuts it with the leaf or sucks it up with the plant sap. Alternatively, if the pest is sprayed directly, the chemical will poison through the ‘skin’ or suffocate the pest.

The method you choose depends on several factors, such as climate, type of insect and type of plant involved.

Non-systemic (‘knock-down’) insecticides

Many early insecticides killed either by blocking the breathing processes or by poisoning when absorbed through other exterior surfaces. But they did not persist for long and had to be used frequently in order to be effective. However, some are still very useful for certain purposes.

Pyrethrum for example, is a very effective general insecticides. It is derived from plants and does not persist for long. This means it are safe to use on vegetables—even up to the day before harvesting. Derris, however, is harmful to fish so do not use it near stocked pools.

Systemic insecticides

The systemic are absorbed by the plant and dispersed throughout its entire system; any biting or sucking insect will ingest them while feeding and be killed. These pest-killers remain in the plant for several days (sometimes even weeks) and they act against a wide variety of pests.

But too often spraying can result in the development of pests that are resistant to them. So spray on sighting the enemy rather than ‘just in case’.

10 top Homemade Organic Pesticides

The following list includes 10 of my favourite, all-natural, inexpensive, homemade, methods for making organic pesticides for your garden.

Neem oil was gather from the Azadirachta indica tree by American Indians and used as a powerful pest control.  In fact it is one of the most powerful natural pesticides know to man containing more than 50 natural insecticides.  To make your own you need 1/2 ounce or 15g of Neem oil (available online) and 1/2 teaspoon of liquid soap in 2 litres/quarts of water and spay immediately.

Works well on Ants: Mix 10 drops of citrus oil with 1 teaspoonful of cayenne pepper and 1 cup of water and poor into the ant colony

Great for Slugs Ants and roaches. Mix 3 tablespoons of liquid soap with 1oz or 30 grams of citrus oil to 1 gallon or 4.5 litres of water.  Shake well then spray onto pests.

For Greenfly and Blackfly control: Mix 30ml of mineral oil with one litre of water, shake and spray into aphids and eggs to dehydrate and kill.

Pulp one large garlic clove and one large onion and add to 1 quart or 1 litre of water. Refrigerate for at least 1 hour then add 1 teaspoon of cayenne pepper and one tablespoon of liquid soap and use within 7 days and keep refrigerated.

Prevents Flies, Midges and Wasps: Use a couple of drops of Eucalyptus oil on a saucer and place on a table or near garden furniture to ward off flies midges and wasps.

For the treatment of spider mite: Mix 2 tablespoons of Sea Salt into one gallon/4.5 litres of warm water and spray on infected areas.

These flowers are a nature source of Pyrethrum. You can make your own insecticide by boiling 100 grams of dried flower heads in 1 litre of water for 20 minutes. Strain the liquid and allow to cool then add to a spray bottle and keep for up to 2 months. Add Neem oil of extra potency.

Use a mortar and pestle to grind 2 dry chilly peppers into a fine dust and mix with 1 cup of Diatomaceous earth. Add 2 litres/quarts of water and let set for 12 hours, shake well before application.

Probably the best know of all the organic pesticides, tobacco spray was commonly used on an agricultural scale for killing pests on crops.

To make your own you will need 1 cup of organic cigarette/pipe tobacco and mix with 1 gallon/4.5 litres of water. Let is stand for 24 hours and drain off the liquid.  This mix can be used on most common garden plants and vegetables except those in the solanaceous family (tomatoes, peppers, eggplants, etc.)