16.8. Cultural control
Subsistence farmers have utilized cultural methods of pest control for centuries, and many of their techniques are applicable to large-scale as well as small-scale, intensive agriculture. Typically, cultural practices involve reducing insect populations in crops by one or a combination of the following techniques: crop rotation, tillage or burning of crop stubble to disrupt pest life cycles, careful timing or placement of plantings to avoid synchrony with pests, destruction of wild plants that harbor pests and/or cultivation of non-crop plants to conserve natural enemies, and use of pest-free root-stocks and seeds. Intermixed plantings of several crops (called intercropping or polyculture) may reduce crop apparency (plant apparency hypothesis) or resource concentration for the pests (resource concentration hypothesis), increase protection for susceptible plants growing near resistant plants (associational resistance hypothesis), and/or promote natural enemies (the natural enemies hypothesis). Recent agroecology research has compared densities of insect pests and their natural enemies in monocultures and polycultures (including di- and tricultures) to test whether the success of intercropping can be explained better by a particular hypothesis; however, the hypotheses are not mutually exclusive and there is some support for each one.
In medical entomology, cultural control methods consist of habitat manipulations, such as draining marshes and removal or covering of water-holding containers to limit larval breeding sites of disease-transmitting mosquitoes, and covering rubbish dumps to prevent access and breeding by disease-disseminating flies. Examples of cultural control of livestock pests include removal of dung that harbors pestiferous flies and simple walk-through traps that remove and kill flies resting on cattle. These exclusion and trapping methods also could be classified as physical methods of control.
