Evaluating, Selecting, and Implementing Pest Management Alternatives
Part 2, Section 1: Pest Management
Activities Involved in an IPM Program
Evaluating, selecting, and implementing pest management alternatives
The IPM concept is based on the premise that all crops can tolerate some levels of pests and that an established pest cannot be eradicated completely. Emphasis is on long-term management of pests to maintain their present level or reduce them to a tolerable level. The principles of IPM are much the same as those of past management methods, but the techniques are becoming more refined. For example, more emphasis is being given to how various management methods affect the overall cropping system. Rather than being focused on a single pest on a single crop, IPM is geared toward managing all pests for the total cropping system used on the farm.
When evaluating pest management alternatives, the farm manager first must determine if the alternative is feasible given available resources on the farm. Basically, it must be determined if enough labor and the proper equipment are available to undertake the pest management alternative. The availability of managerial time and labor are probably the two biggest constraints in adopting certain pest management alternatives.
If you do not have time to devote to the management practice, can you hire such services? If crop consulting services are available in your area, they may provide an economical alternative to handling pest management activities yourself. A related question is whether there is enough flexibility in your cropping system to respond to pests using a particular pest management alternative. If concerns outside of the cropping program predominate — like producing a given type and quantity of feed or forage on limited acreage — then the selection of certain pest management alternatives (for example, crop rotation or alternative enterprises) may be of little or no practical value.
After considering possible resource constraints on your farm, you also must estimate and compare the economic feasibilities of the remaining pest management alternatives. While economic thresholds for many pests have been established for the use of pesticides, many pest management strategies have no straightforward decision rules to assist the producer in making informed, economical pest management decisions.
First, the manager must consider whether the expected benefits of a given pest management alternative exceed its expected costs over time. If several alternatives have expected benefits that exceed expected costs, isolate those that best fit into your operation. Give consideration to the highest level of cost that will be acceptable in implementing this particular pest management practice. If more than one falls into this category, select the one with the greatest expected return. The expected benefit of a pest management alternative is the value of damage averted (in terms of both quantity and quality). Costs of a pest management alternative include the value of any special equipment (amortized over the life of the asset), labor, machinery inputs, materials, managerial time, or services required for the alternative.
Most pest management techniques adaptable to IPM have been known for years. Many were practiced before chemical pesticides came into prominent use. Basic management methods are similar for all crop pests. The five basic types of pest management strategies for agronomic crops include physical, cultural, genetic, biological, and chemical techniques.
- Physical management techniques are direct or indirect measures that eliminate the pest or slow down the growth rate of the pest population. Examples: installing window screens to exclude pests from buildings, hand picking hornworms off tomato plants, and cleaning crop seed to remove weed seed. An example of temperature as a physical management technique can be demonstrated with the corn flea beetle. If the sum of the average temperatures for the months of December, January, and February is below 90°F, beetle numbers will be reduced. Farmers can use temperature to help predict the abundance of certain pests.
- Cultural management practices are used to provide less favorable conditions for pest development. For example, planting wheat after the fly-free date can greatly reduce damage from Hessian fly. Conventional tillage, which buries plant debris, destroys much disease inoculum and overwintering sites for stalk borers, armyworms, and slugs. Narrow row widths and optimum plant populations help agronomic crops compete with emerging weeds. Early harvest may help reduce losses from stalk rot in corn.
Although cultural management has the advantage of being part of routine crop production practices, it often does not adequately manage moderate to high pest levels.
- Genetic management uses tolerance or resistance of plant varieties to certain pests. Varietal resistance is a preferred method for managing certain pests because it usually provides relatively long-term control at low cost. Examples: wheat varieties resistant to Hessian fly, alfalfa varieties resistant to anthracnose and potato leafhopper, and many corn varieties tolerant of or resistant to numerous leaf diseases and European corn borer and corn rootworms. Also, some crop varieties may be more tolerant of pests because they may outgrow pest damage.
Unfortunately, many pests have the ability to develop strains or races capable of overcoming varietal resistance. Therefore, a crop variety with good resistance to a certain pest may be effective only for a few years.
- Biological management involves the use of other living organisms to manage pests. Some of these organisms are native to the area, while others are introduced. For example, parasitic wasps were released throughout the state during 1976–1978 to help manage the cereal leaf beetle. Several introduced parasites and a native fungal disease are helping to keep the alfalfa weevil in check. A native and naturally occurring fungal disease helps minimize the damage of pea aphids on alfalfa.
Biological methods are usually relatively safe, economical, and long-term pest management tactics. However, they are often slow in showing results and lag behind pest outbreaks. Pesticide applications can be detrimental to the effectiveness of these organisms, unless they are well synchronized with the development of the parasites and predators.
- Chemical management involves the application of pesticides. The major advantage of this method is that it can be applied quickly to a given site according to need. It is about the only method a farmer can manipulate and rely on for immediate results. Chemical pesticides, however, have some well-known disadvantages: they may be toxic to humans and other animals; many are harmful to beneficial insects; they usually reduce pest populations only temporarily; resistant strains of pests frequently develop; and some persist in the environment, further endangering many types of organisms. Even with these disadvantages, chemical management is a major aspect of IPM, and pesticides are valuable tools in producing agronomic crops.