Impacts on Insect and Mite Pests - Climate Resilient Agriculture for Ensuring Food Security - page 115

with life cycles beginning earlier in spring and
continuing later in autumn, increase in popula-
tion growth rates and number of generations,
change in migratory behavior, alterations in
crop-pest synchrony and natural enemy-pest
interaction, and changes in interspecifi c interac-
tions (Root et al. 2003 ). Changes in community
structure and extinction of some species are also
expected (Thomas et al. 2004 ).
For species to survive in the changing cli-
mates, they must either adapt in situ to new con-
ditions or shift their distributions in pursuit of
more favorable ones. Many insects have large
population sizes and short-generation times, and
their phenology, fecundity, survival, selection,
and habitat use can respond rapidly to climate
change. These changes to insect life history may
in turn produce rapid changes in their abundance
and distribution. Due to recent climate changes,
widespread, generalist species at their cool range
margins have expanded their distribution ranges,
whereas the ranges of localized, habitat-specialist
species and those at their warm margins have nar-
rowed (Konvicka et al. 2003 ). An array of meth-
ods including surveys, experiments, and modeling
have been used to study the impact of climate
change on pest abundance and distribution.
Insect pests of crop plants are the real candi-
dates most affected by global climate change.
Complex physiological effects exerted by the
increasing temperature and CO 2 may affect pro-
foundly the interactions between crop plants and
insect pests (Roth and Lindroth 1995 ). It has
been reported that global climate warming may
lead to altitude-wise expansion of the geographic
range of insect pests (Elphinstone and Toth
2008 ), increased abundance of tropical insect
species (Bale et al. 2002 ; Diffenbaugh et al.
2008 ), decrease in the relative proportion of
temperature-sensitive insect population (Petzoldt
and Seaman 2010 ; Sharma et al. 2005 , 2010 ),
more incidence of insect-transmitted plant dis-
eases through range expansion, and rapid multi-
plication of insect vectors (Petzoldt and Seaman
2010 ). Thus, with changing climate, it is expected
that the growers of crops have to face new and
intense pest problems in the years to come.

The climate change-led changes in insect pest
status will perilously affect agricultural produc-
tion and the livelihood of farmers in the country
where larger portion of work force is directly
dependent on climate-sensitive sectors such as
agriculture (Chahal et al. 2008 ). This envisages
an urgent need to modify crop protection mea-
sures with changed climate in order to attain the
goal of food security of the nation.
Insects being poikilotherms, temperature is
probably the single most important environmen-
tal factor infl uencing their behavior, distribution,
development, survival, and reproduction (Bale
et al. 2002 ; Petzoldt and Seaman 2010 ).
Therefore, it is highly expected that the major
drivers of climate change, i.e., elevated CO 2 ,
increased temperature, and depleted soil mois-
ture, can impact population dynamics of insect
pests (Fig. 7.1 ) and the extent of crop losses sig-
nifi cantly (Petzoldt and Seaman 2010 ).
High mobility and rapid population growth
will increase the extent of losses due to insect
pests. Many species may have their diapause
strategies disrupted as the linkages between tem-
perature and moisture regimes, and the day length
will be altered. Genetic variation and multifactor
inheritance of innate recognition of environmen-
tal signals may mean that many insect species
will have to adapt readily to such disruption.
Global warming and climate changes will
result in:
• Rising temperatures extend geographical

range of insect pests.
• Increased overwintering and rapid population
growth.
• Changes in insect-host plant interactions.
• Increased risk of invasion by migrant pests.
• Impact on arthropod diversity and extinction
of species.
• Changes in synchrony between insect pests
and their crop hosts.
• Introduction of alternative hosts as green
bridges.
• Reduced effectiveness of crop protection
technologies.

• Increase in pesticide sprays.

• Faster resistance to pesticides.