NORTH-SOUTH CENTRE - ETH - North-South Centre North-South ...

Control options for the African root and
tuber scale on cassava
The African root and tuber scale Stictococcus vayssierei
is a major pest in the forest zone of Central Africa where
it infests at least ten cultivated crops with greatest
occurrence on cassava. In southern Cameroon, our research
has focused on understanding factors responsible for the
recent increase in pest status of S. vayssierei. The scale is
closely associated with the ant Anoplolepis tenella, which
is considered essential for scale survival and dispersal. One
of the key questions that we have addressed in the process
of developing scale control options is the question about
the nature of its interactions with the ant A. tenella, and
the conditions that promote the abundance and proliferation
of the ant. In initial studies, we monitored ant diversity
in the predominant vegetation types in the forest zone of
southern Cameroon. Furthermore, we collected various
associated data to determine the factors affecting the observed
distribution. We then conducted laboratory and
screenhouse experiments to understand how A. tenella
interacts with other dominant co-occurring ant species, and
we completed experiments that demonstrated the role of
A. tenella in scale dispersal. Subsequently, we devoted much
of our efforts to the development of baits for A. tenella.
We found that the boric acid-sucrose liquid bait was the
most promising bait for A. tenella control. We are presently
testing this bait in participatory field experiments on
eight farms.
From the data collected to date, average A. tenella abundance
was significantly lower in fields with boric acid
ant bait compared with control fields. Similar trends were
observed for S. vayssierei abundance, certainly due to lower
ant abundance in ant-baited fields compared with control
fields. These trends are a first large-scale experimental
confirmation that A. tenella control can reduce S. vayssierei
abundance.
We are looking forward to obtaining the remaining ant
and scale sampling from the ant control trial. Currently, our
main activities are monitoring the ongoing experiment and
preparing manuscripts on the completed experiments. In
addition, we initiated a protocol on ant competition that we
will be complementing within the next few months.
68 Research fellow
Apollin Fotso Kuate, IITA, Cameroon
Capacity development
Research fellowships
Supervisors
Peter Nagel, University of Basel, Switzerland;
Rachid Hanna, IITA, Cameroon
Collaborators
Maurice Tindo, University of Douala, Cameroon;
Georg Goergen, IITA, Benin
Duration
November 2006 – December 2010
Groundnut and cassava planting in Awae, Cameroon