IPM Strategy 3. Modifying the Climate

Perhaps the most familiar example of pest management by climate management is the use of refrigeration for foods like fresh fruits and vegetables. Most consumers have seen their favorite produce items mold and decay, but careful maintenance of the cold chain from harvest to consumer greatly reduces such food losses. Within a given growing area, certain methods can change the effective crop environment by modifying the microclimate in which the plants grow.

One aspect of the microclimate has to do with the nature of reflected light. In the late 1970s, scientists discovered that growers could use reflective mulches on vegetable beds to confuse aphids that spread damaging viruses to squash plants. As one article from 1979 states, “the mulches reflect the sun’s ultraviolet rays, which the aphids ‘see’ instead of the blue-green light of the plants. In effect, they receive a signal to ‘keep flying’ instead of landing.” Tarps are also widely used to block light getting to weeds so that they are not able to grow and compete with the crop.

Vineyard following “leaf removal” to modify the canopy microclimate (Photo by Andy Allen, Univ. Missouri)

Wine grape growers often use trellising methods and remove lower leaves to change the microclimate where the grape clusters are developing. By lowering the humidity, it is possible to reduce damage by fungal pathogens such as Botrytis bunch rot.

A variety of growing systems, called protected culture, range from a simple rain shield to a passive greenhouse to a high-tech greenhouse with complete climate control. These measures provide relief from certain diseases that would otherwise be fostered by rain. They also provide other advantages, such as an extended growing season.

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Hoop houses for raspberry production in the Salinas Valley of California (photo by Steve Savage)

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