Elements Of An IPM Program

Planning and managing production systems

The greater the level of knowledge about a crop and its enemies, the more the chance there is to prevent organisms from becoming pests and so minimize damage.

Establishment of economic/damage/action thresholds:

The economic injury level (EIL), also called the damage threshold, is defined as the lowest population density that will cause economic damage, economic damage being the amount of injury which will justify the cost of artificial control measures (Stern et al. 1959). The EIL depends upon four factors: the market value of crop, the cost of control, the injury per pest density (injury/pest x number of pests) and the loss in crop value per pest injury (Morse and Buhler, 1997).

Crop protection action is not considered until the pest population approaches the level at which economic injury could occur. The pest population is checked on a regular basis, and if it reaches the economic threshold (ET) then pesticide is applied.

Monitoring

Below: Traps used to monitor insect population.

Regular visits to the fields are very important. They permit early detection of any problem before it becomes out of control and even facilitates the discovery of an unexpected enemy. These visits can also reveal if any pesticide intervention was efficient. Monitoring the level of a pest population and its natural enemies in the field may sound relatively easy, but in practice it can be quite difficult.  Even though it is the most basic element of any IPM program, it still remains one of the greatest challenges to making IPM work well.

Sampling methods can be direct (the pests themselves are assessed) or indirect (damage or some other indicator is used). Although thresholds are usually based upon number of pests found in a sample, the economic injury threshold (EIL) concept is really based on the level of crop injury.

Application control measures

There are numerous preventive measures that can be easily adopted and that give good results in the fight against harmful organisms.

Cultural control

Cultural control employs practices that make the environment less attractive to pests and less favorable for their survival, dispersal, growth and reproduction; they also promote the pest's natural controls. Some examples are:

Crop rotation:

potential insect pest and disease problems increase when a crop is planted into its own residue from the previous season, and even more so for many years in a row (referred to as mono-cropping) instead of planting into the residue of an unrelated crop. This method has proven to be efficient over the centuries. Depending on the pest problems encountered, the rotation can be short (2-3 years) or long (4-7 years). Crops susceptible to the same type of pests should be placed as far apart as possible.

Intercropping and interseeding encourage an increase in natural control agents.

Stripcropping with non-host plants

By filling in space with non-host plants, spread between rows becomes more difficult.

Trap crops

Trap crops are planted next to the commercial crop to deter predation, a trap crop is one that is preferable to the pest than the main crop, and can be destroyed if pest populations are high enough that they may spread over to the commercial crop. For example, researchers at the Pest Management Research Center in Vineland, and the Horticultural Experiment Station in Simcoe, Ontario, have found Indian mustard to be an effective trap crop for crucifers. The mustard attracts flea beetles, striped cucumber beetles, and crucifer beetles, and also provides refuge (and food) for many beneficial insects.

Synthetic mulches

Synthetic mulches are used to discourage insect pest, and organic mulches create favorable habitat for natural pest control.

Destruction of infected material

Sanitary disposal of infected leaves, fruit, weeds or other plant tissues that provide overwintering sites for pests.

Use local plants

Choose crops and varieties that are adapted to the climate and that are resistant to enemies. Biotechnology offers substantial potential in this area.

Below: good seeds can make a crop worthwhile.



Clean and healthy seeds and plants

Clean seeds avoid weed problems. Seeds bought commercially have been separated from any weeds that might have harvested along with the crop; farmers who grow their own seeds for re-planting can take the seed to a mill to have any weed seeds removed. It is important to note that it is difficult for plants with a low rate of germination to fight against weeds and that many diseases are transmitted by "sick" seeds or plants.

Diversify the "weapons" used:

If the same pesticide is always used, the target pest organisms will eventually develop resistance, rendering the pesticide ineffective. It is important to diversify the group type of pesticides used and also to use alternative means to fight against harmful organisms.

Mechanical control

Strip harvesting helps to prevent the mass migration of natural enemies of pests from the field following crop harvest. Leaving a band of the crop in the field helps to maintain a stable ecosystem, as well as providing deeper snow cover for winter protection of perennial crops.

A badly infested crop can be harvested early if other control measures are not available to save the crop, as otherwise it would be lost.

Cultivation will control insects in soil by exposing larvae and pupae to natural control agents, and by damaging or burying adults. Cultivation through chisel plowing, for example, also provides soil conservation advantages.

Physical barriers or trapping techniques prevent insects from reaching the crop. They include row covers, trenches or sticky boards, tapes and nets for flying insects.

Irrigation and drainage can assist with controlling insects through specific lifestyle or reproduction habits which are dependant on water availability or absence. Also, plants which are having difficulty to grow because of too much water in the soil, are less resistant disease and insects.

Tillage at the right time can delay the germination of the weeds until the crop is strong enough to compete with them. The germination of some weed seeds is stimulated by a "flash" of light by the ground being opened up during tillage; cultivating at night prevents these weeds from germinating. Other practices can delay the "outing" of insects from the ground and even reduce their population levels.

(Physical Control of Pests, 1996)

Biological control

Specifically, biological control helps to reduce pest populations through the use of natural enemies and is a component of an integrated pest management strategy. The earliest successful introduction of insects as control agents was carried out in the late 1800's to control cottony cushion scale in California citrus orchards. In the United States, exotic (imported) species now represent 40% of all agricultural insect pests.

Control of insects

For insects, natural enemies are classified as predators, parasitic or pathogenic. Predator control agents are non-specific in their mode of action, which is direct and simple. The predator will prey on certain pests during its life time, eliminating the pest from the environment. Lady beetles and lacewings are predators released on a widespread basis as a biological control strategy in greenhouses. Parasitic control agents have an immature life stage (i.e. as larvae) that develops on or within a specific single insect host, ultimately killing the host. Parasite types are mostly wasps or flies. Pathogenic control agents, also known as disease-causing organisms, are bacteria, viruses and fungi. They are frequently referred as bio-insecticides and are specific to certain groups of insects and particular phases of their life cycle. The effectiveness of such bio-insecticides relies on an understanding of the pest's life cycle. Bacillus thuringiensis (Bt) is an important commercialized bacteria formulation widely used by gardeners and crop producers; it has proven very effective as a non-chemical pesticide against corn borer.

Control by birds

In orchards, birds, such as woodpeckers, tits, swallows, wrens, and certain raptors and also bats are useful for controlling pests. It is then important to encourage and maintain their presence by building birdhouses, by providing shelters (i.e. cedar bushes) and water throughout the orchard.

Weed control

For weeds, natural enemies can be insects or pathogenic. Since most weeds have been introduced from other parts of the world, natural enemies that control their spread are not always present. Introducing natural enemies from the weeds original "home" can help a great deal in controlling a weed population. A frequently cited example of successful weed control by an insect is the destruction of the prickly pear cacti (Opuntia; spp.) in Australia by an imported moth (Cactoblastis cactorum). Plant pathogens (disease-causing organisms) offer two advantages as biocontrol agents of weeds: they are often more host specific, and they can be applied with conventional spray equipment at a time when the weed is at its most susceptible stage.

Disease control

Finally, in combating plant diseases, they are referred to as antagonists. Antagonistic control agents help to successfully inoculate the host against plant disease and food spoilage microorganisms. They are applied post-emergent to the plants, on the soil and around the roots, and to plant seeds according to critical factors such as moisture, nutrient availability and soil acidity. Antagonists are non-toxic to humans, resistant to pesticides, compatible with other treatments and non-pathogenic to the host plant.

Chemical control

Such products are classified in several ways, which is important information at the time of selection, whether it be for insecticides, herbicides or fungicides. Their capacity for selectivity with regard to the targeted pest determines their level of toxicity. Their mode of action and active ingredient is also the basis for classification. Once the economic threshold due to a pest has been reached, methods of chemical suppression are the most frequent means used to combat the pest. Pesticide resistance and water quality are the main long-term concerns from using such controls.

Bio-insecticides are less toxic than chemical products to humans, livestock and the environment in general. They are also more selective in their effect and therefore less harmful to existing natural control agents (beneficial insects.) They include microbial-based insecticides (pathogens), insect-based chemicals such as pheromones, insect growth regulators and insecticidal soaps.
(Biological Control: A Guide to Natural Enemies in North America)

Other examples of alternative organic chemicals are rotenone, pyrethrum, nicotine, sulfate, neem and sabadilla. Even though they are derived from plant materials these chemicals still produce significant levels of plant and human toxicity and are worth special care in their handling and application.
(Steve's Garden Pest Workshop)

Evaluation of the effects and efficacy of pest control measures used

This a fundamental element of a good IPM program since it is from the evaluation of what measures worked and did not work that the next action plan is drawn up.

Profile

Monitoring pest populations is an essential component of pest management for Richard Behm, an organic horticultural crop farmer in St-Alexis. Cabbage maggots are his biggest pest problem, and early detection (and control) of the first adult flies to emerge in the spring is key to control for the rest of the season. Cabbage maggots have 4 generations per year, the most damaging of which is the first.

Behm has trial plots in his and other farmers' fields, testing different pest control methods, new cultivars, and plant spacing. He keeps up with new information through the Internet and various universities and researchers in Canada and the US.

Cabbage maggot flies are caught in traps randomly placed throughout the field; the traps are counted every four days in order to know exactly when the flies appear. Soil samples are taken from around cabbage roots and analyzed for pupae.