Pesticides in an Integrated Pest Management Approach

Table of Contents

1. Introduction
2. Systemic Pesticides
3. Contact Pesticides
4. When To Use Pesticides
5. Related Links

Introduction

The term pesticide is used to describe a variety of chemicals: insecticides that control insects; fongicides that control diseases caused by fungi; herbicides or weed-killer compounds that control weeds; and others.

Insecticides are specifically formulated to control certain insects. Preventive sprays must be applied before eggs are laid.

Fungicides help control and prevent fungal diseases. Preventive applications are necessary to protect leaves and fruit against infection. If applied after infection takes place, most fungicides can not stop development of the disease, but they may prevent further spread. Repeat applications are required to protect new growth and to renew protection. Fungicides are not harmful to bees. Apply fungicides before rainfall to allow residue time to dry and reduce loss during rainfall.

Only those pesticides with a Domestic label are listed in this manual. Products having a commercial, agricultural or restricted label should not be used by the home gardener.

Pesticides are listed by active ingredient only. When buying a pesticide product, select the appropriate material based on active ingredient and label information. There are usually several products that will provide the desired control. Sources for pesticides include local garden centres, hardware stores and similar retail outlets.

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Systemic Pesticides

A systemic insecticide or fungicide is one that is absorbed by the leaves and stems or by the roots and moves with the sap inside the plant. Sap-sucking insects such as aphids, leafhoppers and leaf-miners are controlled, but beetles, caterpillars and wood borers are not. Dimethoate and oxydemeton-methyl are examples of insecticides having a systemic action. Benomyl and triforine are examples of systemic fungicides. Spray applications are used for systemic leaf and stem pesticides; soil applications deliver systemic root pesticides.

There are advantages to systemic pesticides. Once absorbed, the systemic action of these chemicals counteracts uneven spraying or washing-off by rain. Systemic insecticides can also act as stomach poisons and contact sprays; systemic fungicides can kill fungus spores that land on a treated leaf. However, systemics do not provide permanent control. They gradually breakdown within the plant and are diluted by new plant growth or as they disperse throughout the plant.

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Contact Pesticides

A contact insecticide or fungicide is neither absorbed into the plant nor moved through the plant by the sap. As its name implies, it works externally by direct contact with the insect or disease. To be effective therefore, the pesticide must completely cover the plant or affected plant areas. An even application technique is also important to ensure full coverage and full contact. For example, because two-spotted mites are found primarily on the underside of leaves, coverage of the lower surface is essential to achieving good control.

When plants grow rapidly, applications must be made frequently to protect the new growth.

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When To Use Pesticides

It is normal for garden plants to suffer some damage from pests. Healthy plants can withstand pest attack better than those growing under difficult conditions. A few blemishes on fruit or spots on leaves are not usually worth the cost and time spent in control efforts. To be economical, the cost of control should be less than or equal to the loss sustained. It is up to you to decide how much damage you can realistically tolerate or accept before resorting to the use of pesticides.

Nearly all fruit and vegetable crops attract pests that will cause damage if not controlled. Often, the most serious pests are those not native to Canada, but which have been inadvertently introduced. They multiply freely in the absence of predatory and parasitic insects found in their original habitat. Some also find our climate favourable for a rapid increase during the growing season. When this is the case, or if a high yield, high quality crop is your goal, pesticides may be the only valid control strategy available to you.

To use the minimum amount of required pesticide most effectively, you must identify the target pest and determine its life cycle and biology. This includes the damaging stages of the pest, when the pest is present and when it is most vulnerable in its life cycle. All control measures are time sensitive. To be effective, they must be applied at the proper developmental stage of the pest.

Always select a product recommended for your particular pest problem and spray only the infected plants to avoid killing beneficial insects in the garden. Under no circumstances should you apply a pesticide in the hope of curing an unknown problem. Before using any pesticide, read the label and follow the instructions.

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Related Links

• Master Gardeners
• Landscape Ontario
• Integrated Pest Management

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