Cultural Control Methods

Table of Contents

1. Integrated Pest Management
• Cultural Control Methods
• Planning
  • Companion Planning
  • Crop Diversity
  • Crop Rotation
  • Crop Selection
  • Plant Hardiness
  • Soil Drainage
• Growing
  • Climate
  • Planting Time
  • Depth and Spacing
  • Sanitation
  • Tilling
  • Water
  • Weed Control
• Harvesting
2. Related Links

Integrated Pest Management

An integrated pest management strategy is one that combines cultural, natural, mechanical and chemical pest control measures. Many of these measures on their own might not provide sufficient control, but in combination, they can reduce the problem to below threshold levels. It is the most effective and environmentally friendly way to minimize problems in your garden.

To plan a successful integrated pest management program, it is important to be familiar both with the plants in your yard and with each one's specific growth requirements. This will help you understand the types of pests most likely to be en­countered. Monitoring yard and garden plants frequently throughout the growing season is important. Control is much easier if applied when pest populations are low. As well, healthy plants can withstand pest attack better than plants growing under one of several différent environmental stresses.

If you wish to avoid the use of pesticides, carefully select the plants to be grown in your garden, discarding those that will likely require chemical control. For example, avoid hybrid tea roses if you do not wish to spray for blackspot, a disease that will defoliate the plants by mid-to-late summer. Choose instead some of the old-fashioned and species-type roses which are not susceptible.

Cultural Control Methods

The following are cultural pest management options that must be considered if pesticide use is to be minimized or eliminated.

Planning

Companion Planting

Companion planting is the inter‑planting of crops with other plants thought to repel or prevent pest outbreaks. It is advocated by some as an effective control technique. Unfortunately, a three‑year study conducted by staff of the Pest Diagnostic Clinic disproves this belief.

Cabbage, potato, and roses were planted in test plots, and companion plants thought to have insect repellent characteristics were planted around and within them. These included basil, bean, catnip, celery, chives, dill, flax, garlic, geranium, hyssop, horseradish, French and African marigold, nasturtium, parsley, peppermint, sage, tansy, thyme, tomato, and wormwood. All plants were maintained using organic methods.

At the end of the study, it was found that not only were pests generally unaffected by the companion plants, but the companion plants competed with the crops for moisture, nutrients and sunlight. The overall result was reduced crop yield and quality. The only combination which consistently showed some promise was the interplanting of beans and potatoes to reduce injury from Colorado potato beetles and potato leafhoppers.

If you still want to try companion planting as a pest control measure in your garden, several techniques may improve the likelihood of success:

• avoid close planting of highly competitive, densely foliated plants near the crop. For example, avoid planting African marigold, catnip, celery, tansy, tomato, and wormwood as companions unless sufficient space is allowed;
• avoid wormwood, as it produces a chemical substance that reduces the growth of nearby plants;
• avoid companion plants that serve as alternate hosts for pests or diseases of the crop. For example, flea beetles will attack nasturtium as well as cabbage;
• choose plants of aesthetic or culinary importance which could also provide enjoyment or food;
• always leave some of the crop without companion plants to objectively assess whether or not any benefit is resulting from this technique.

Crop Diversity

If a wide variety of plants are grown in a small location, it is more difficult for flying insects to find the right plant on which to feed. For this reason, inter-cropping, or planting alternating varieties of crops, can help reduce pest problems more than if crops are planted in large blocks.

Crop Rotation

Crop rotation involves the planting of non-related crops in a particular location in successive years to minimize the chances of plant-specific disease organisms and pests building up in the soil. This is practical only in large gardens and fields. In small home gardens where rototillers, foot traffic, water and wind readily move soil from one part of the garden to another, it is of limited value. Crop rotation can be effective when certain crops are not planted for two to four years if a particular disease is present, or if certain plants can be successfully planted in remote parts of the garden over successive years.

Crop Selection

Plant breeders have incorporated genetic resistance to various diseases and pests into plants. It is now possible, therefore, to select non-susceptible or resistant plant varieties for your garden. Information on resistant varieties is available from seed catalogues or you can ask nursery or garden centre staff when buying plants.

Plant Hardiness

Not all plants are adapted to all sites, climatic zones, soils, soil pHs, light availability or similar environmental conditions. Plants that grow in unsuitable locations are predisposed to diseases, insects and secondary problems. Woody and herbaceous perennial plants are given hardiness zone ratings that correspond to geographic regions of Ontario and Canada. Buy only those plants that carry a hardiness rating equal to or higher than your location.

Soil Drainage

Good soil drainage is essential as soil saturated with water for several days may cause roots to rot.

Growing

Climate

Climate can greatly influence the health of your garden, and though you have no control over climate, you can be aware of its effects, and take counter-measures when appropriate.

Climate has an effect on insect populations. Fewer generations are produced in cold areas than in warm. Late spring frosts and cold, wet springs are harmful to newly hatched larvae. Heavy rainfall washes small insects such as mites and aphids from plants.

Climate can also influence the severity of a disease. A cool wet spring, for example, increases the severity of Anthracnose on white oak, sycamore, and ash. Frequent summer showers increases the incidence of botrytis on flowers such as tulips, geranium, roses and petunias.

Planting Time

Planting time can be critical to avoid the egg-laying stage of many pests. Optimum times are provided for several garden vegetables (see Table 9).

Planting time can also be critical to minimize the potential for seed and seedling rot. Do not plant large seeded vegetables when the weather is cool and moist, as seed rot can easily overcome the seedlings before they emerge. Wait until the soil is warm and moist.

Depth And Spacing

Planting at the proper depth ensures that seedlings emerge quickly and reduces the risk of damping-off fungi. Even, wide spacing guards against crowding, which can lead to spindly succulent growth, poor ventilation and poor drying conditions. These increase the likelihood that problems such as botrytis, white mould, root rots, damping-off and foliar diseases will develop.

Sanitation

As many insects and diseases overwinter in plant debris and in weeds, the most important sanitation measure involves the regular removal of such material. Pull up all infected plants and weeds promptly and dispose of them outside the garden. They should either be sent to the garbage or buried at least 60 cm deep. Do not put diseased plants in the compost pile, as the sustained high temperatures required to kill problem-causing insects, nematodes, fungi and weed seeds cannot be guaranteed. Some insects overwinter under boards, bricks, stones and similar objects. Remove all such hiding places and store them away from the soil.

Sanitation also includes careful attention to the health of new plants or seeds introduced to your garden. Use only high quality, pest-free and disease-free planting material and seeds.

Tilling

Tilling is important not only to prepare the soil for planting, but to protect the health of your plants. When you work the earth, diseased plant material is incorporated deep into the soil. It is then more rapidly broken down by soil micro-organisms. As a general rule, harmful pathogens survive poorly on rotted plant material or when deep in the soil, and so their levels are effectively reduced.

In addition, tilling exposes soil borne insects, slugs and other invertebrates to adverse weather conditions and to predators such as birds. Many will also be killed by the tilling process itself.

Water

Many diseases are spread by spores which require moisture on leaves and stems to germinate and cause infection. If diseases that are spread by splashing are present in your garden, avoid overhead watering. Water in the morning so that plants dry before nightfall. Do not work in the garden when plants are wet, as you may unwittingly spread disease when you brush against them.

Weed Control

Some weeds serve as reservoirs for insects and diseases. They also compete for nutrients and moisture. Season-long control is recommended.

Harvesting

Crops left too long in the garden are more susceptible to pests or storage rot diseases. It is important therefore both to harvest on time and to properly prepare the crop for storage. Avoid rough handling of fruits and vegetables. This can cause wounds which, in turn, can become infected by secondary disease agents.

Related Links

• Master Gardeners
• Landscape Ontario
• Integrated Pest Management

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