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dens (Walker); and beet armyworm larval survivorships increased and development was
hastened in soybeans that were irrigated compared with dryland-grown soybeans (Huffman
& Mueller, 1983). These observations suggest that soft-bodied lepidopteran larvae that live
on plant surfaces exposed to the desiccating effects of direct sunlight and ambient air (unlike
lepidopteran stalkboring larvae that live in moist plant interiors) are especially vulnerable to
the desiccating effects of insufficient water supply.
4. Some non-nutrient-related associations of water deficit with
phytophagous arthropods
Host plant selection among insects also involves visual and physical factors such as leaf
shape, color, and size (Ramaswamy, 1988; Renwick & Radke, 1988; Renwick & Chew, 1994;
Showler & Castro, 2010b), and both constitutive and inducible plant chemical defenses can
vary in response to water deficit stress (Lombardero et al., 2000), but visual and physical
cues, and defensive compounds are not considered as being nutritional for the purposes of
this chapter (although defensive compounds might loosely be considered as being types of
nutrients, they mostly repel, interfere with feeding, or act as toxins). Concentrations of sev‐
eral classes of defensive secondary compounds tend to increase in plant tissues in response
to moderate drought, including terpenoids (some of which are attractants (Mattson &
Haack, 1987) and alkaloids (Gershenson, 1984; Hoffmann et al., 1984; Sharpe et al., 1985;
Lorio, 1986; Mattson & Haack, 1987; Showler, 2012), but intensified drought stress can lead
to reductions of these compounds (Mattson and Haack, 1987). Drought can also influence
predator and parasitoid guilds that affect phytophagous arthropod populations (Showler,
2012), but plant stress is not directly involved. Other mechanisms that might also contribute
toward plant vulnerability to herbivorous arthropods under conditions of water deficit
stress have been suggested (Mattson & Haack, 1987), including acoustical cues, detoxifica‐
tion of foods by drought stressed insects, and drought-induced genetic changes in arthro‐
pods, but they have not been well substantiated.
5. Multiple effects of water deficit: case study on sugarcane and the
Mexican rice borer
The Mexican rice borer, Eoreuma loftini (Dyar), and its association with sugarcane is arguably
one of the most illustrative examples of how an economically important phytophagous ar‐
thropod is affected by limited availability of water. The crambid moth is indigenous to west‐
ern Mexico (Morrill, 1925; Van Zwaluwenberg, 1926) where it is a major pest of sugarcane,
but it had spread by the mid 1970s to Veracruz, San Luis Potosi, and Tamaulipas in eastern
Mexico (Johnson, 1984). First detected in the United States in the Lower Rio Grande Valley
of Texas in 1980 (Johnson, 1981, 1984; Johnson & Van Leerdam, 1981), the pest dispersed in‐
to rice producing areas of east Texas (Browning et al., 1989; Reay-Jones et al., 2008), and in
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