54 / 124
September 2017
52
The effect of CA on insects and
ecosystem services
C
onventional agriculture practices
such as continuous tillage lead to
the disruption of soil structure and
loss of fertile top soil, resulting in
a reduction of soil productivity. Conser-
vation agriculture (CA) is recognised as a
way to combat soil deterioration brought on
by conventional cultivation.
CA practices in crop production systems
may provide different habitats for hosting
and supporting pests and may influence
beneficial insect populations including un-
derlining biodiversity that supports many
ecosystem services.
Insects play many important roles within an
ecosystem such as predators, pollinators,
detritivores, herbivores and parasitoids.
They are efficient indicators of ecosystem
functions, ideal to monitor the quality of a
habitat and to observe how a site changes
from time to time, and to measure habitat
differences.
There is a general lack of information and
statistics concerning the effect of CA on ar-
thropod diversity, and the potential ecosys-
tem services they provide in South Africa.
To understand the impact of landscape
structures on the diversity and abundance
of beneficial and harmful arthropods, pest
regulation and ultimately crop yield can be
of significant help to enhance the manage-
ment of agricultural landscapes.
During the growing seasons of 2014/2015,
2015/2016 and 2016/2017 arthropods were
sampled via pitfall traps in the Ottosdal,
Hartbeesfontein, Sannieshof, Vredefort and
Kroonstad areas where well-established CA
and conventional farming systems were im-
plemented.
Arthropods are invertebrate animals of
the large phylum Arthropoda, such as in-
sects, spider, or crustacean. A total number
of 40 000 soil-dwelling arthropods and
197 morphospecies were collected dur-
ing this study from 14 different orders and
30 different families.
The term morphospecies is defined as
organisms that are classified in the same
species if they appear identical by morpho-
logical criteria.
Morphospecies as well as their abundance
at a certain time can be tracked to the date
of occurrence and what treatment were
used along with the type of crop planted
(
Table 1
). To prevent crop damage by in-
sects, it is essential to monitor and inspect
the crop fields regularly. The identification
of morphospecies and data recorded are
of great value to monitor the density of the
occurrence of pests.
Over the past three growing seasons the
number of morphospecies was significantly
higher in a CA system as compared to the
conventional systems. Therefore, tillage
practices may target certain morphological
species types (
Graph 1
).
The overall total number of individuals
was significantly higher in a CA system than
conventional farming system. CA contrib-
utes in supporting a higher and richer biodi-
versity (
Graph 2
).
To determine if CA can provide ecosystem
services by controlling pests with beneficial
insects, the Chilo borer (
Chilo partellus
) was
used. Larvae and pupae of the Chilo borer
(
Photo 1
) were pinned onto petri dishes to
monitor the predator activity between CA
and conventional farming systems.
FOCUS
Integrated pest control
Special
HEIDI MEYER
and
DR ANNEMIE ERASMUS,
ARC-Grain Crops, Potchefstroom
Graph 1: Overall morphospecies recorded in
the two treatments in 2015 - 2017 (F= 10,568;
P= 0,003).
Graph 3: The percentage predation on Chilo
borer larvae in CA compared to a conventional
system.
Graph 4: The percentage predation on Chilo
borer pupae in CA compared to a conventional
system.
Graph 2: Overall number of individuals caught
in CA and a conventional system in 2015 - 2017
(F= 6,386; P= 0,017).
1: Chilo borer larvae and pupae pinned on
petri-dish to be placed in a cage to monitor
predation.
1
Category box and whisker plot: Species
Treatment
CA
CA
CA
CA
Conventional
Conventional
% predation of Chilo borer larvae
% predation of Chilo borer pupae
Conventional
Conventional
Treatment
Category box and whisker plot: Total individuals
Total individuals
Species