July 2002 - Integrated Pest
Management for the Home Gardener
By Donna DuBour, Master Gardener
The IPM approach compels you to consider your landscape as
part of the larger urban or suburban community ecosystem to manage
responsibly. The impact of your gardening and pest management
decisions often extends far beyond your property lines.
Integrated Pest Management is the process of integrating several methods of pest and disease control (biological, cultural and chemical) to control pests and disease with the least impact on the environment, beneficial insects and human health.
Integrated Pest Management is not a strictly organic approach to pest control. When necessary, chemicals are employed as a last resort. With the carefully managed use of an array of pest control tactics, including biological and cultural methods you can achieve the best results with the least disruption of the environment.
IPM is a decision making process. Each plant, each year and each habitat are slightly different. A set schedule of treatments will not take into account these differences. Therefore, monitoring must be performed and decisions must be made. IPM is a system of pest management decisions based on ecological, economic and sociological values. IPM is a process of pest monitoring and sampling. We must know the status of a pest and whether it really needs a control action or not.
IPM is a process, which considers all of the control options.
The basis for IPM is the understanding that many crops can withstand a certain amount of pest damage. As a result, a rescue treatment is not needed until the pest population reaches a critical level usually referred to as a threshold. In the home vegetable garden, this threshold may be economic, but is more likely to be aesthetic. On the other hand a commercial grower' s produce and or plants must be blemish free (or nearly so) for marketing. If a cabbage is found to have holes in the leaves from insect feeding, it will probably be discarded or sold at a lower price. Nursery plants full of disease and/or insects will certainly not attract many buyers. These problems affect the livelihood of the growers, making the threshold economic. On the other hand, the threshold for homegrown vegetables or flowers is often dependent on an individual gardener's tolerance to the damage.
Thresholds for different pests may vary greatly. In the case of the striped or spotted cucumber beetle, a pest on melons and cucumber plants and a vector of bacterial wilt disease, the threshold is only one actively feeding beetle in the entire planting. Other pests however may be present in larger numbers and not effect a plants long-term health.
Pests develop resistance to chemical treatments. Frequent spraying hastens pesticide resistance. Using chemical controls when they are not needed disrupts the natural control mechanisms, predators, parasites, and competitors that help suppress pest populations.
Take time to become familiar with the plants in your landscape, the pests that are attracted to them, their life cycles and the damage they cause. Taking the necessary steps to provide the best possible growing conditions will limit disease development in most cases. Choose resistant cultivars. Below are listed some of the things you can do to reduce the likeliness of disease in your landscape and your dependence on chemicals as the sole means of dealing with pests. Start with the proper environment.
Start from the ground up:
Incorporate organic matter in flower and vegetable beds on a regular basis.
Have a soil test done every two to three years and adjust the pH accordingly.
Fertilize as needed to maintain vigor.
Avoid over fertilizing plants, as it can lead to pest problems.
Maintain even soil moisture.
Prevent weed-growth and soil erosion.
Protect plant roots and crowns from winter damage.
Select well-adapted varieties for the site conditions.
Select disease or insect resistant varieties.
Purchase healthy, certified, disease-free seeds, transplants and nursery stock.
Plant at the right time.
Select suitable sites for the selected plants.
Prepare soil correctly.
Water newly planted trees and shrubs deeply (2" of water) every 1 to 2 weeks as needed.
Avoid overhead watering and splashing soil onto plants.
Water trees and shrubs slowly and deeply. Remember that the root zone can extend out 2 to-3 times the height of the tree beyond the drip line.
Use drip irrigation and soaker hoses where practical.
Weeds rob plants of moisture and nutrients and are alternate hosts for pests and diseases.
Prune to increase air circulation.
Avoid accidental root pruning when cultivating and tilling.
Do not work with plants when foliage or soil is wet.
Use floating row covers to prevent pest problems. (Removing to allow for pollination.)
Remove and dispose of diseased or infested plant parts and dead plants.
Rake up and dispose of diseased leaves and fruits.
Clean up and compost garden debris in the fall.
Use soiless planting media.
Use clean, sanitized seedling flats and plant containers.
Do not over-water.
Acclimatize transplants that are grown indoors by slowly introducing them to outdoor conditions.
Protect new transplants and seedlings from cutworms and slugs with paper collars.
Non-Chemical Control Strategies For Pests And Diseases
Learn to tolerate some damage Most healthy herbaceous and woody plants can tolerate 20-30% leaf defoliation without suffering long-term damage or yield reduction.
Wait for the “good bugs” Aphid feeding in the spring alarms many gardeners, myself included. Natural predators and parasites usually clean up local infestations in a month or so.
Remove plant or plant parts: Simply removing and disposing of badly damaged plants may minimize the problem on adjacent plants and prevent recurrence.
Timing of seeding and planting: Some pests can be circumvented by growing vulnerable plants when damage is least likely. For example, late summer squash crops are less troubled by squash vine borer. This requires knowledge of pest life cycles.
Late fall or early spring tillage: Many pests over-winter in the crop debris of host plants or in the soil around host plants. Tilling can disrupt pest habitats.
Water stream A strong hose spray may temporarily dislodge mites, aphids and other pests. Be careful not to damage plants.
Hand picking: Pick off adult and immature insects and egg masses. Pests can be squashed or dropped into a jar of soapy water.
Grow pest resistant or tolerant plants: Check with the nursery or gardening catalogs when selecting plants for those with resistance or tolerance to pests and diseases. Many native plants are good choices.
Do not over fertilize: Aphids and spider mites will produce more young on over fertilized plants.
Barriers: A floating row cover is an excellent material for excluding insect pests. Other examples are paper collars for cutworms and diatomaceous earth for slugs.
Rotation: Rotate crops that are prone to pests and diseases. However, it is often very difficult to rotate away from disease problems in small gardens that over-winter in soil or garden debris.
IPM is a decision making process.
Many pests and diseases do not need to be controlled on older or mature plants. However, problems that develop on seedlings, transplants, and newly planted trees and shrubs may need a control decision. For environmental problems, the site and/or cultural conditions may need to be modified to correct the problem.
Key Plants
Key plants are trees, shrubs and flowers, which are known to have perennial pest problems. As an example, birch trees always get leaf miners, aphids and borers. The same is true with Hostas and slugs, columbine and leaf miner, or bearded iris and borers. By familiarizing yourself with your plants and the diseases and pests common to them it will help you make a decision about what, if anything needs to be done.
Key Pests are those, which cause significant damage or may kill trees, shrubs or perennial flowers. These key pests often have special times that they are susceptible to controls. Aphids or galls in oaks are rarely significant enough to warrant controls while peach tree borers in ornamental plums need special attention
Think Pest Management versus Pest Eradication.
Realistic thresholds should be set for insects and diseases. The presence of a pest doesn’t always mean treatment is necessary. It is very important to identify the pest or disease and become familiar with its life cycle. Some pests and diseases may require control, while others may not. Often by the time disease or insect damage is observed, it is too late to do anything about the problem until next season.
Treatment decisions depend on the type of plant that has a problem. If a plant is easy to replace such as an annual, just pull the problem plant and replace it. Plants that continue to grow throughout the season will often outgrow the pest or disease damage. Predators will keep the pest numbers in check in many instances.
Once you have identified the problem and determine that it requires treatment, select a control strategy. Always select the least toxic solutions first such as physical (hand removal, change watering practices, pruning out damage, etc.) and biological (encourage beneficials, release predatory mites, etc.). Pesticides should be used selectively (spot treatments) with the least toxic materials (B.t., insecticidal soaps, horticultural oils, etc.) used first. Continue to monitor the plant’s health after treating a problem to determine if further action is needed. By following these steps the occurrence of insect and disease problems in your landscape will be greatly diminished. If problems should arise try the remedy with the least impact on the environment and on human health.