Authors: (Allan T. Showler, Kika de la Garza Subtropical Agricultural Research Center, USDA-ARS IFNRRU, Weslaco, Texas, USA)
Abstract: In addition to making otherwise arable regions less, or nonarable, from lack of lifesustaining
water, water deficit also affects the extent to which crops are afflicted by
arthropod pests. The effects of drought on host plant availability and nutritional value
influence arthropod pests of crops in a variety of ways that can benefit or detract from
crop production. In the arid Sahel region of Africa (roughly from Mauritania to Sudan),
for example, the effect of variable rainfall is associated with desert locust, Schistocerca
gregaria (Forskål), plagues that can devastate crop production from the Cape Verde
Islands to India. Water deficit stress can also lead to host plant accumulations of proteins,
carbohydrates, free amino acids, and other nutrients that favor insect growth and
development, sometimes leading to outbreaks, as in the cases of bark beetles in forests,
and accelerated insect infestation in field crops. Insects can also benefit from drought
when dry conditions suppress or exclude predator and parasite populations that would
otherwise help mediate populations of pests. Water deficit in host plants can be
unfavorable to insect pests because decreased plant turgor hinders fluid uptake by plantsucking
arthropods, desiccation of insects exposed to ambient heat can occur, and
increases in secondary defensive plant compounds (e.g., phenolics) and lignification of
plant tissues may render the plant unsuitable. Strategies to ameliorate drought-associated
pest problems, including use of drought tolerant crop varieties, soil amendments to
improve water retention, heightened surveillance, and the use of more efficient irrigation
practices are discussed.
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