Impacts on Nematode Pests - Climate Resilient Agriculture for Ensuring Food Security - page 178

exceeds US$ 100 billion annually. The losses are
5.8 % greater in developing countries than in
developed countries (Sasser and Freckman 1987 ).

greenhouse gases is posing a serious challenge to
sustainability of crop production by interfering
with biotic and abiotic components and their
interactions with each other. Global warming
resulting in elevated carbon dioxide (CO 2 ) and
temperature in the atmosphere may infl uence
plant pathogenic nematodes directly by interfer-
ing with their developmental rate and survival
strategies and indirectly by altering host plant
physiology. Available information on effect of
global warming on plant pathogenic nematodes
though limited indicates that nematodes show a
neutral or positive response to CO 2 enrichment
effects with some species showing the potential
to build up rapidly and interfere with plant's
response to global warming. Studies have also
demonstrated that the geographical distribution
range of plant pathogenic nematodes may expand
with global warming spreading nematode prob-
lems to newer areas. Besides plant parasites,
other trophic groups (microbial feeders, preda-
tors, and insect parasites) of soil nematodes also
have shown to infl uence the plant productivity
indirectly by regulating the key ecosystem pro-
cesses including decomposition, nutrient miner-
alization, biological pest suppression, and energy
transfer in food webs. These fi ndings underline
the importance of understanding the impact of
climate change on soil nematodes and its
implications to crop production while developing
mitigation and adaptation strategies to address
impact of climate change on agriculture.
Nematodes by virtue of their trophic diversity
occupy a central position in soil food webs and
play an important role in providing vital ecosys-
tem services. Acting directly as pests and indi-
rectly as vectors of other plant pathogens and
consumers of microfl ora and fauna, nematodes
play a signifi cant role in regulating plant growth,
biological pest suppression, and nutrient cycling
in agroecosystems.

9.2 Climate Change

and Nematodes

Soil nematodes are dependent on the continuity
of soil water fi lms for movement. Their activities
are largely controlled by soil biological and
physical conditions (Yeates and Bongers 1999 ).
Scientifi c research on climate change and its
impact on herbivorous nematodes are very limited.
However, based upon their environmental require-
ments, some assumptions are possible. Severe
droughts resulting in a reduction of soil water will
most likely negatively affect soil nematodes. Higher
average temperatures will probably have little
effect, since thermal conductivity of soils is low.
Apparently, a prediction of how climate
change will affect herbivorous soil nematodes
and thus yields cannot be made. There is some
evidence that population dynamics may change,
but so far no trend is clear. Basically, and most
likely true for all ecological research, the impacts
of climate change are specifi c to crop/plant,
region, and interacting species.
The majority of plant pathogenic nematodes
spend part of their lives in soil, and therefore, soil
is the source of primary inoculum. Life cycle of a
nematode can be completed within 2-4 weeks
under optimum environmental conditions.
Temperature is the most important factor, and
development is slower with cooler soil tempera-
tures. Warmer soil temperatures are expected to
accelerate nematode development, perhaps result-
ing in additional generations per season, and drier
temperatures are expected to increase symptoms
of water stress in plants infected with nematodes
such as the soybean cyst nematode. Overwintering
of nematodes is not expected to be signifi cantly
affected by changes in climate, although for some,
such as the soybean cyst nematode, egg viability
may be reduced in mild winters.
Plant pathogenic nematodes are one of the
important biotic constraints in crop production.
Climate change due to increased emission of

9.3 CO 2 Enrichment

CO 2 concentration plays a crucial role in various
aspects - biology of plant and insect parasitic
nematodes including host recognition, recovery