Impacts on Insect and Mite Pests - Climate Resilient Agriculture for Ensuring Food Security - page 135

or increased winter survival (Harrington et al.
2001 ; Sharma et al. 2005 ; Petzoldt and Seaman
2010 ). Disruption of synchrony between insect
pests and their natural enemies may upset the
natural biological control (Petzoldt and Seaman
2010 ). Certain pesticides like pyrethroids and
organophosphates and especially the biopesti-
cides being highly thermo-unstable degrade
faster at higher temperatures. Altered tempera-
ture regimes may render many of these products
to be less or not effective in pest control, neces-
sitating frequent insecticide applications for
effective control (Musser and Shelton 2005 ).
This may intensify the pest problems due to the
increased chances of resistance development in
insects. Ultimately it will add to increased cost of
crop protection to the farmers and in turn envi-
ronmental cost (Musser and Shelton 2005 ;
Petzoldt and Seaman 2010 ). The forewarning
models for predicting insect arrival/infestations
based on earlier climate profi les need to be
revised in accordance with location-specifi c
changes in climate in order to provide precise and
accurate forecast of pest incidence.
A number of cultural practices that can be
used by farmers could be affected by changes in
climate - although it is not clear whether these
practices would be helped, hindered, or not
affected by the anticipated changes. Using crop
rotation as an insect management strategy could
be less effective with earlier insect arrival or
increased overwintering of insects. However, this
could be balanced by changes in the earliness of
crop planting times, development, and harvest.
Row covers used for insect exclusion might have
to be removed earlier to prevent crop damage by
excessive temperatures under the covers - would
the targeted early insects also complete their
damaging periods earlier or be ready to attack
when the row covers were removed?

success. This means that it is likely that farmers
in the northeastern USA will have more types
and higher numbers of insects to manage. Based
on current comparisons of insecticide usage
between more southern states and more northern
states, this is likely to mean more insecticide use
and expense for northeastern farmers. New York
conditions currently require 0-5 insecticide
applications against lepidopteron insect pests to
produce marketable sweet corn (Stivers 1999 );
Maryland and Delaware conditions require 4-8
insecticide applications (Whitney et al. 2000 );
Florida conditions require 15-32 applications
(Aerts et al. 1999 ). It is apparent that for sweet
corn pests, warmer temperatures translate to
increased insecticide applications to produce a
marketable crop. Insecticides and their applica-
tions have signifi cant economic costs for growers
and environmental costs for society. Additionally,
some classes of pesticides (pyrethroids and spi-
nosad) have been shown to be less effective in
controlling insects at higher temperatures
(Musser and Shelton 2005 ).
Entomologists predict additional generations of
important pest insects in temperate climates as a
result of increased temperatures, probably necessi-
tating more insecticide applications to maintain
populations below economic damage thresholds. A
basic rule of thumb for avoiding the development
of insecticide resistance is to apply insecticides
with a particular mode of action less frequently
(Shelton et al. 2001 ). With more insecticide appli-
cations required, the probability of applying a
given mode of action insecticide more times in a
season will increase, thus increasing the probability
of insects developing resistance to insecticides.
Tilman et al. ( 2001 ) foresee a 2.4-2.7-fold
increase in pesticide use by 2050 related to popu-
lation growth and conversion of natural ecosys-
tems to agriculture, but the effect of climate
change is not considered by the authors. Chen
and McCarl ( 2001 ) investigated the relationship
of temperature, precipitation, and pesticide costs
for several crops in the USA and concluded that
increases in rainfall lead to increases in average
pesticide costs for corn, cotton, potatoes,
soybeans, and wheat, while hotter weather
increases pesticide costs for corn, cotton,

7.17 Increased Pesticide Usage

It is likely that farmers will experience extensive
impacts on insect management strategies with
changes in climate. Entomologists expect that
insects will expand their geographic ranges and