Sustainable Agriculture Literature Review - Boulder County

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Pests
Plant pests will most likely be affected by climate change due to rising temperatures and
changes in regional precipitation. Plant pests include weeds, insects, fungi, viruses, and
bacteria that cause plant diseases. A study published in the New England Journal of
Medicine conducted on the impacts of climate change and human health found that an
increase of pests and pathogens would be a likely outcome of climate change due to an
imbalance in the agricultural ecosystem. 43 Weeds can benefit from climate change for
several reasons. For example, some weeds may be favored because of an increase in
soil moisture, or a decrease in soil moisture depending on more precipitation or drought
during a given time period. 44 It is difficult to predict an accurate scope of the effects of
climate change on weeds, but the crop-weed relationship will be altered. 45
Insect pests and pathogen life cycles will be affected by climate change in various ways.
First, an increase in temperature for cumulative days could cause an increase in insect
generations. Second, and most relevant in the temperate zones, is winter survival. For
instance, if there are not enough consecutive days below a certain temperature, some
insects will be able to continually regenerate. Third, certain populations of insects may
shift regions of prevalence due to environmental change. A simulation was conducted on
the European corn borer that predicted a shift of the species northwest up to 165 and
500 km for each 1 o C rise in temperature. 46 The exact effects of climate change on the
relationship between crops and pests are not yet certain, but it is known that their
relationship will alter.
Depending on the degree to which climatic conditions are altered, the occurrence of
plant fungal and bacterial pests could increase or decrease. As climate change begins to
affect temperature, rainfall, humidity, and radiation, the spread of pathogens, as well as
the resistance to pathogens from host plants, will change. Not including genetic
modification of crops, there are several crop diseases that will be favored due to the
occurrence of milder winters. Furthermore, warmer summers could provide a decrease
in the prevalence of such diseases as the potato blight. Although this would be a positive
outcome, there is a chance that overall prevalence of plant diseases will not decrease,
but will instead move to regions with more favorable environmental conditions. 47
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