**3. Systems in agriculture and the situation of IPM as a sub-system**

Spedding [44] defined a system as a group of interacting components, operating together for a common purpose, capable of reaching as a whole to external stimuli. A system is unaffected by its own output and has a specified boundary based on the inclusion of all significant feedbacks. However, four types of systems are generally acknowledged in ag‐ riculture including ecosystem, agroecosystem, farming systems and cropping systems (Figure 1). In this hierarchy, a system may consist of several sub-systems. IPM is a subsystem of cropping system and considered as the operating system used by farmers to manage population of crop pests. This sub-system has a degree of independence and can be studied in isolation of the cropping system. It has its own inputs and has the same output as the main system (i. e. yield) but relates to only some of the components and therefore, to only some of the inputs [45].

IPM systems have a goal of providing the farmer with an economic and appropriate means of controlling crop pest. The aim should be to devise an IPM system which is suf‐ ficiently robust to maintain control over a prolonged period of time [46]. However, to achieve an IPM system a number of attributes will require including: (*a*) provide effec‐ tive control of pest; (*b*) be economically viable; (*c*) simplicity and flexibility; (*d*) utilize compatible control measure; (*e*) sustainability and (*f*) minimum harmful effect on the en‐

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First and foremost the IPM system must be effective. For the farmer this means that this sys‐ tem should be at least as good as the conventional control methods. The system should be economic. No farmer will adopt and sustain use of uneconomic pest management practices. On the other hand, an IPM system must be designed to be as simple as possible, utilizing the minimum number of control measures compatible with maintaining pest populations at ap‐ propriate levels. The individual control measures should of course be compatible and opti‐ mize natural mortality factors. It is important during design of an IPM system to consider the level of control which is required and the best mix of control measures that will achieve this with minimal antagonism. Finally, the IPM system should be sustainable, have mini‐ mum impact on the environment and present no hazard to the farmer, their families or the

Following widespread concerns about the adverse effects of insecticides it became clear that calendar spraying was not the appropriate approach to pest control. In fact, determining whether an insect control measure (usually an insecticide) is "needed" is one of the basic principles of any IPM programme. "Need" can be defined in a number of ways, but most growers associate the need for an insecticide with economics. In other words, most growers ask some form of these questions: "How many insects cause how much damage?", "Are the damage levels all significant?" and "Will the value of yield protection with an insecticide offset the cost of control?" Therefore, researchers from different agricultural disciplines came to realize that a decision rule or threshold should answer such questions and that pest

Pest management is a combination of processes that include obtaining the information, deci‐ sion making and taking action [41]. In assessing, evaluating and choosing a particular pest control option, farmer's perception of the problem and of potential solutions is the most im‐ portant factor (Figure 2). Decision making in pest management, like other economic prob‐ lems in agriculture, involves allocating scarce resources to meet food demand of a growing population. In this process, agricultural producers have to make choices regarding the use of several inputs including labor, insecticides, herbicides, fungicides, and consulting expens‐ es related to the level and intensity of pest infestation and the timing of treatment. However, decision making process for pest control takes place in many levels at the fields. These vari‐ ous layers of decision making affect the whole strategy of pest control in a given cropping

control must be viewed as a decision making process (Figure 2).

vironment, producer and consumer.

consumers of the crop products [45].

**4. Decision making in IPM**

**Figure 1.** A hierarchy of systems in agriculture

IPM systems have a goal of providing the farmer with an economic and appropriate means of controlling crop pest. The aim should be to devise an IPM system which is suf‐ ficiently robust to maintain control over a prolonged period of time [46]. However, to achieve an IPM system a number of attributes will require including: (*a*) provide effec‐ tive control of pest; (*b*) be economically viable; (*c*) simplicity and flexibility; (*d*) utilize compatible control measure; (*e*) sustainability and (*f*) minimum harmful effect on the en‐ vironment, producer and consumer.

First and foremost the IPM system must be effective. For the farmer this means that this sys‐ tem should be at least as good as the conventional control methods. The system should be economic. No farmer will adopt and sustain use of uneconomic pest management practices. On the other hand, an IPM system must be designed to be as simple as possible, utilizing the minimum number of control measures compatible with maintaining pest populations at ap‐ propriate levels. The individual control measures should of course be compatible and opti‐ mize natural mortality factors. It is important during design of an IPM system to consider the level of control which is required and the best mix of control measures that will achieve this with minimal antagonism. Finally, the IPM system should be sustainable, have mini‐ mum impact on the environment and present no hazard to the farmer, their families or the consumers of the crop products [45].
