Integrated Pest Management (IPM)
Healthy organic gardens are full of bugs. Gardens, and even farms, are ecosystems that maintain their own balance. Thousands of species of insects and other invertebrates make their homes in the soil and on the plants we grow. In a balanced garden ecosystem, pest species are the exception, and infestations are rare.
In an organic approach to growing crops, we feed the soil with organic matter and encourage abundant and diverse soil ecology. When the soil is healthy, the plants we grow in it will be more vigorous, and better prepared to deal with stress.
Integrated Pest Management is an ecological approach to pest control that focuses on prevention, observation, and thoughtful, careful intervention only when needed. In this system, chemical pesticide is employed only after all other avenues of control have been exhausted.
The Six Principles of Integrated Pest Management:
1. Acceptable Pest Levels
The goal is not to eradicate all pest insects from the garden or farm, but rather to control their population. Not only is it next to impossible to remove an entire pest population, but doing so would put pressure on the rest of the ecosystem. In IPM, we establish acceptable pest population levels, or “action thresholds.” Only if the action threshold is crossed do we need to intervene.
The action threshold is specific to the pest insect, and also specific to the site in question.
Pest species that are allowed to survive reduce “selection pressure.” This stops the pest developing resistance to chemicals produced by the plant or applied to the crop. Maintaining non-resistant pests is an important consideration.
2. Preventive Cultural Practices
a. Selecting the right plant variety for the site in question.
b. Crop rotation.
c. Maintaining healthy crops.
d. Sanitation – keeping the growing area clean and free from diseased plants, hiding spots for slugs, etc…
e. Employing physical barriers such as row cover or netting.
f. Planting to attract predatory insects
Regular observation is the central tenet of IPM. It is broken into two categories. The first category is inspection. The grower physically inspects plants for signs of pest insects, damage, or other stresses. Traps like sticky cards can be used to monitor population levels. Random samples can be taken. Careful monitoring of a crop will reveal the when the action threshold is first broken.
The second category of monitoring is identification. Correctly identifying the pest species, and understanding its life cycle, is central to its control. For instance, many insects are more susceptible to biological control in the larval stage than they are as adults. Some families of insects (moths and butterflies, as opposed to beetles) share a common susceptibility to certain treatments.
Record keeping is essential. Insect populations rise and fall, and their behaviour changes, at different times of the year. When do they first appear in the spring? When are they actively laying eggs? At what point in the season do you notice crop damage, and which plants are most affected?
4. Mechanical Controls
Once you have established that an action threshold has been broken, and you have correctly identified the insect, the first methods of control are mechanical. Some pests are large enough to be hand picked from the plants. Others, like aphids, can be dislodged with a blast from the hose. Places where the pests might be breeding or hiding out during the day can be removed. Barriers such as row cover can be put in place. Traps can be installed. Some insects like whitefly can be vacuumed up. Other insects, like wireworm, can be exposed by tillage, and then picked over by chickens.
5. Biological Controls
This level of control attempts to exploit existing natural relationships between the best insect and other organisms such as bacteria, entomopathogenic fungi, predatory nematodes, and beneficial insects such as predatory wasps, mites, beetles, and so on. These systems have a minimal environmental impact, and are often very cost effective. For most of these controls to work, you must have a positive identification of the pest species.
6. Responsible Pesticide Use
This “last resort” attempt to control the problem may not even be an option for organic growers. Before employing synthetic chemical pesticide, it’s worth reconsidering what you are trying to grow. It may be that the population of pests in your area is simply not manageable, and that you must re-examine your goals or methods. Some chemical pesticides can at least be derived from naturally occurring chemicals such as nicotine, pyrethrum, and neem oil. But once these chemicals are introduced to your garden ecosystem, the results are very hard to predict. These chemicals are not target-specific, and may impact beneficial insects, pollinators, birds, amphibians, fish, pets, and so on.
Even in large scale, chemically dependent farm systems, IPM can reduce human and environmental exposure to chemical pesticides, and save a great deal of money. For the organic grower IPM is the obvious logical way to manage pests. In British Columbia, the Integrated Pest Management Act regulates the sale, sue, and handling of all pesticides in the province and promotes the IPM approach to managing pests. The Ministry of Environment oversees the Act and its implementation.