Rotation with cover crops, grains, and vegetables in different families from the crop is probably the most effective way to prevent buildup of insects, diseases, and weeds. The greater the differences between plants in rotation, the more effective they are in suppressing pest populations. For example, alternating upright crops, such as tomatoes and peppers which are widely spaced in rows with crops such as leafy greens which are planted densely on beds will interrupt weed life cycles, as will alternating between cool and warm season crops. To the extent that crop rotation improves soil structure and fertility, crops grown in rotations should also be better able to tolerate or outgrow pest damage. Although rotation will almost always offer some reduction in pest problems when compared to continuous cropping, it is most effective in reducing pests with a narrow host range and those that cannot survive more than one or two years without a host.
Rotation is of little help with highly mobile insects.
While we usually think of IPM in relation to insect pests, IPM principles also apply to weed and disease control. The successful practitioner must know when and how to sample and how much crop damage current pest populations will cause if uncontrolled. Knowing whether the amount of damage predicted will reduce net returns, that is, whether damage exceeds the economic injury threshold. The economic threshold is the point at which the predicted dollar value of losses from pest damage exceeds the cost of control. Determining the best control or management strategy when predicted damage exceeds the economic threshold.