34 ■ DISEASE & PEST CONTROL
C&CI
Coffee wilt disease is one of
March 2010
the greatest natural disasters Out of Africa? Wide-
ever to afflict African coffee
production. If concerted action
is not taken, it will inevitably
ranging effort needed
spread, says CABI’s
commodities specialist,
to control CWD
Dr Peter Baker
the implementation of these recommen-
dations led to the status of CWD being
D
uring the last decade of the 20th reduced to that of a minor coffee disease.
Century, there was a resurgence in Excelsa on the other hand, never recov-
an almost forgotten African fungal ered as a commercial crop.
disease called coffee wilt disease (CWD), In 1957, CWD was found for the first
which quickly became become the princi- time on Arabica in Ethiopia. For many
pal production constraint for Robusta cof- years it was a minor problem there, the
fee in Uganda and the Democratic disease being less aggressive than on
Republic of Congo (DRC). Over the same Robusta. However, in recent years the
period, a similar disease of Arabica cof- problem has grown, to the point that it is
fee, present since the 1950s in Ethiopia, now widely regarded as serious.
became a growing problem.
Why this happened is both a mystery
and a tragedy – a mystery because we
A Robusta tree killed
understand so little about the origins of by coffee wilt disease
Discolouration of coffee wood is a
the disease; a tragedy because such a
diagnostic feature of CWD.
major outbreak, which has now cost
about a billion Dollars in lost earnings, trolling coffee diseases –
could have been avoided. spraying on appearance
CWD is of special significance of early symptoms – whol-
because, unlike other major coffee dis- ly inappropriate with CWD.
eases, it kills the tree. The first signs of it Hence a proactive (pre-
are a wilting of the leaves, which then ventative) approach to dis-
curl, dry up and fall. Most affected trees ease management is
die two to three months after initial symp- required.
toms are observed. The symptoms are
confirmed by removing the bark of a dis-
Resurgence
Outbreak
eased stem to reveal a blue-black stain Through the 1960s and 1970s the Robusta
on the wood underneath.
and spread
disease more or less disappeared, but this
Once a tree is infected there is no rem- CWD was first discovered in 1927 in a changed in the late 1970s with occasional
edy other than to uproot and burn it in plantation of Excelsa in the Central reports of it in DRC, on abandoned farms in
situ to reduce spread of infection. Thus African Republic. By 1938 it had spread Oriental Province.
the arrival of the disease suddenly to Cameroon, then DRC in 1939 and Côte By the late 1980s the disease had
changes Robusta from being, as the d’Ivoire in 1947 with major losses there become widespread, spreading south
name suggests, a strong tree capable of into the 1950s. In 1958, the disease was towards North Kivu with incidences of 30
withstanding attack from several dis- reported in Guinea causing coffee pro- per cent not uncommon. CWD was discov-
eases, into one that easily succumbs. It duction to fall nearly 50 per cent. ered in Uganda in 1993 and it quickly
can turn coffee from being a source of From the late 1950s, a control pro- spread to most of the country. In subse-
ready seasonal cash for poor farming gramme began to a) systematically quent years Ugandan coffee production fell
families into a liability that represents uproot and destroy affected coffee plants by about 5 per cent and much of this
wasted time and effort. over vast areas, b) relocate coffee pro- decline can be directly attributed to CWD.
Smallholder farmers, if they control cof- duction to new locations, and c) replant The disease was next found on Robusta in
fee diseases at all, are used to dealing with resistant trees. This strategy proved NW Tanzania in 1995, though the spread
with problems on a ‘just-in-time’ basis highly successful in eradicating the dis- and intensity of the disease there is to date
rather than a ‘just-in-case’ approach. But ease from Côte d’Ivoire and DRC. To this much less than in Uganda or DRC.
by the time the farmer realizes he has date the former country remains free of Hence a disease that was thought to
CWD, it is too late to take action. This the disease, a remarkable testament to have been consigned to history has
makes the conventional approach to con- the programme’s effectiveness. Overall, returned, causing major damage.
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