Dr Astrid Jankielsohn,
ARC-Small Grain Institute, Bethlehem
C
limate change and agriculture are interrelated
processes which both
occur globally. Global
warming is projected to have significant impacts on conditions
affecting agriculture, including
temperature, carbon dioxide, precipitation and the interaction of
these elements. The changes in
climatic conditions caused by
global warming can potentially
have significant impacts on global
food security since the challenge
to produce enough food for the
human population will be directly
influenced by a changing climate.
Many studies of climate change
effects on crops have focused on
potential yields, but factors such
as insect pests have major effects
in determining actual yields.
Because insects are cold blooded,
their body temperature varies
with the surrounding temperature
and they are therefore strongly
influenced by climate. Climatic
parameters can directly influence
insects by affecting their rate of
development, reproduction, distribution, migration and adaptation.
Climatic changes could therefore
have a significant impact on the
development, distribution and
population density of agricultural
insect pests. Because aphids are a
group of insects with a relatively
short generation and low developmental threshold temperatures,
they can be expected to be greatly
influenced by climatic changes.
The Russian wheat aphid
(Diuraphis noxia (Kurdjumov)) belongs to a group of alien aphid
species that are capable of surviving even at low numbers for a
relatively long time and even causing population outbreaks in a new
area (Fig. 1). The Russian wheat
aphid has spread from its native
area in central Asia to most of the
major wheat producing countries
in the world and became an international wheat pest. Currently,
the Russian wheat aphid is considered a primary pest of dryland
winter wheat in North America
and South Africa. There are currently four Russian wheat aphid
biotypes recorded in South Africa,
RWASA1 (recorded in 1978);
RWASA2 (recorded in 2005);
RWASA3 (recorded in 2009);
RWASA4 (recorded in 2011).
Fig. 1 Russian wheat aphid population on wheat