Insect Pests of Potato - The Potato: Botany, Production and Uses - page 134

extremely low damage tolerances in their har-
vested product and/or have small profit margins.
This often drives aggressive pest management
regimes aimed at avoiding small percentages of
crop damage and maximizing yield per hectare.
Potato is an important food crop around the
world, resulting in extensive research and gen-
eral publications on potato entomology over the
past 100 years. Some valuable publications in-
clude a recent book covering potato entomology
(Giordenengo et al ., 2013), the insect-related
portions of the recently revised Potato Health
Management (Johnson, 2008), and the basic
biology of several insect-transmitted diseases as
discussed in Stevenson et al . (2001). Nowadays,
of course, much valuable information is available
online. Good starting points for finding online in-
formation on potato entomology include the web-
sites of the Potato Association of America ( http://
potatoassociation.org/ ) , the European Association
for Potato Research ( http://www.eapr.net/ ) , and the
International Potato Center ( http://cipotato.org/ ) .
Our aims for this chapter are to introduce
pests and categories of pests of nearly global sig-
nificance, to discuss important management
considerations, and to provide a set of useful ref-
erences as starting points in the potato entomol-
ogy literature.

Fig. 9.1. Colorado potato beetle early (a) and late
(b) larval instars and adult (c). (Drawings by Dylan
Vermeul, Richland, Washington, USA.)

Distribution

The Colorado potato beetle is believed to be na-
tive to the central highlands of Mexico, where
the primary host plant is believed to be buf-
falobur, Solanum rostratum (Casagrande, 1987). It
was first reported as a major pest to cultivated
potato in 1859 near Omaha, Nebraska, USA (Jacques,
1988). Though the species is capable of significant
dispersal, most of the spread of Colorado potato
beetle has been attributed to, or inadvertently fa-
cilitated by, humans. Currently, the Colorado po-
tato beetle is an established pest of potato in North
America, Mexico, Europe, Central Asia, Asia Minor,
western China, and Iran (Weber, 2003). The wide
distribution and colonization of colder climates
by the Colorado potato beetle can be attributed
largely to facultative overwintering diapause.
This diapause, or resting stage, is triggered
by short days, cold temperatures, and reduced
host food quality (de Kort, 1990). When dia-
pause is triggered, adults burrow 10- 25 cm
deep into the soil. This behavior allows survivor-
ship past harsh winter temperatures. Diapause
lasts at least 3 months, and exit from diapause
and resumption of normal life-stage activity is
triggered by soil temperatures above 10°C. Males
and females exit diapause synchronously and
begin mating prior to colonizing host plants. Not
all individuals exit diapause at the same time,
and some individuals have been noted to remain
in diapause for more than 2 years.

9.1 Chewing Pests

Colorado potato beetle
(Coleoptera: Chrysomelidae)

Recognition

The Colorado potato beetle, Leptinotarsa decem-
lineata , is the most widely recognized pest of po-
tato. Colorado potato beetles develop through
four larval instars before pupating. The larvae
are orange to red in color, with black head and
legs, and two rows of black dots along the sides
(Fig. 9.1a-b) . Adults are 10 mm long and 7 mm
wide, pale yellow in color, with five black stripes
on each wing, and covered with black markings
on the head and pronotum ( Fig. 9.1c ) . Eggs are
laid in clusters of 20-40 on the underside of
leaves, with each egg being 1.5 mm long and
yellow when newly laid, but turning to orange
prior to hatching. Female Colorado potato bee-
tles can lay 300- 800 eggs in their lifetime.