Pests and Diseases of Coffee in Eastern Africa:
A Technical and Advisory Manual
compiled & edited by
Mike A. Rutherford
CABI UK Centre (Ascot)
and
Noah Phiri
CABI Africa Regional Centre (Nairobi)Acknowledgements
The authors would like to thank all those who contributed towards the
preparation of this manual, in terms of provision of information, photographic
material and advice. Gratitude is also extended to the United Kingdom
Department for International Development (DFID) for providing financial
report through the Renewable Natural Resources Research Strategy Crop
Protection Programme (RNRRS CPP).
Copyright statement
© Copyright CAB International (2006)
Extracts of this publication may be freely reproduced and distributed on a
non-commercial basis for teaching and training purposes only, providing that
the source is clearly acknowledged as:
CAB International (2006) Pests and diseases of coffee in eastern Africa: a
technical and advisory manual. CAB International, Wallingford, UK
Compiled & edited by Mike Rutherford and Noah Phiri
The copyright works may not be used for any other purpose without the
express written consent of CAB International (trading as CABI), and such
notice shall be placed on all copies distributed by whatever means.
This publication is an output from th e Crop Protection Programme of the UK
Department for International Development (DFID), for the benefit of
developing countries. The views expressed are not necessarily those of DFID.
2CONTENTS
Page no.
Part 1 Introduction 4
Part 2 Coffee Pests 7
Coffee Berry Borer 8
White Coffee Stem Borer 12
Green Scales 16
Coffee Root Mealybug 21
Nematodes of Coffee 24
Part 3 Coffee Diseases 29
Coffee Leaf Rust 30
Coffee Berry Disease 35
Coffee Wilt Disease 39
Coffee Bark Disease 45
Brown Eye Spot Disease 49
Sources of Information and Further
Reading 51
Glossary of Technical Terms 55
3Part 1
INTRODUCTION
Coffee is grown in more than 50 countries around the world and, although
utilised in a number of ways, is produced primarily for consumption as a
beverage by more than one third of the world’s population. It is a major
commodity on the global market and provides a source of revenue for many
millions of people concerned with cultivation, marketing, export and
processing of the crop. Globally, Brazil is the biggest exporter of coffee,
providing 25 million bags (each 60 kg) in 2003, which accounted for more
than 30% of world coffee exports. Although many species of coffee exist,
commercial production is based principally on two, Coffea arabica and
Coffea canephora . These are often referred to as arabica coffee and
robusta coffee, respectively. More than 60% of global coffee production is
based on C. arabica . This species is considered to produce beans of higher
quality and therefore demands a higher market value. However, C.
canephora is better suited to warmer and more humid tropical environments
than C. arabica and, also able to withstand more adverse conditions, is often
grown at lower altitudes. Furthermore, C. canephora is generally more
resistant to coffee pests and diseases.
Over the last two decades the level of coffee production has gradually
increased, largely due to liberalisation of markets, while the price of coffee on
the world market has declined and has become more prone to fluctuations.
This has implications for those involved in the coffee commodity chain,
including coffee farmers who still endeavour to produce a crop of
acceptable quantity and quality but for reduced economic returns. Under
such conditions farmers find it increasingly difficult to acquire those resources
required for good crop management. Achieving satisfactory control of
prevailing pests and diseases, one of many factors that producers must take
into consideration, becomes increasingly difficult.
Coffee is an important commodity for Africa, Uganda being the biggest
exporter (2.5 million bags in 2003). As in other parts of the continent, and
indeed across the world, the majority is produced by smallholder farmer
families that tend to have little in the way of resources to manage their farms.
In these situations women often take responsibility for day-to-day running of
the farm, the income from coffee being used for everyday needs including
the purchase of food, clothing and me dicine, payment of school fees and
cultivation of other crops. Fortunate farmers may be in a position to raise
cattle, goats, chickens or other animals for production of milk, eggs and meat
and as source of manure. In terms of tackling pest and disease problems,
resource-limited smallholder farmers are heavily reliant on the use of cultural
management practices, ensuring a vigorous crop though application of
4mulch and manure, monitoring pest and disease levels and ensuring good
sanitation, as opposed to the use of artificial fertilisers and chemical
pesticides. In some cases coffee is produced on larger scale monocultures
that, due to higher income levels, tend to be more mechanised, have trained
staff, rely more heavily on fertilisers and chemical pesticides and may have
irrigation systems. Here the possibilities for applying more complex and
expensive approaches to management are much greater.
In Africa, as elsewhere, coffee farm ers are continuously threatened by a
range of pest and disease problems. Many of these are minor in terms of the
damage they cause and their effect on yield and quality. However some,
such as coffee berry disease, coffee leaf rust and coffee wilt disease
(tracheomycosis), can be very serious indeed and can have a major impact
not only on individual farmers but on the economy of countries or regions
heavily dependent on coffee for fore ign exchange earnings. Coffee wilt
disease, for example, has been known to exist in Africa since the 1920s but
renewed and widespread outbreaks of the disease since the 1990s has
already led to considerable losses in Uganda, where more than 14 million
trees have been destroyed, and in the Democratic Republic of Congo. Once
established on a farm this disease is very difficult to control. Given the
perennial nature of coffee, some pests and diseases are able to survive and
multiply throughout the cropping season and are always present on the
coffee crop, although their populations and hence their effect on the crop
may vary through the year. Others may only visit and attack coffee during
periods when conditions are favourable . Either way, the damage they cause
and their impact on crop yield and quality can be considerable. White
coffee stem borer, coffee wilt disease, parasitic nematodes and root mealy
bug, for example, can and often do kill a coffee plant. Coffee berry borer,
green scales, leaf rust and brown eye spot, however, will have more of a
debilitating effect on plant growth, by causing defoliation for example, and
can seriously affect berry quality.
It is vital that farmers are aware of the threats presented by pests and
diseases and of appropriate steps that may be taken to help prevent their
occurrence and to tackle them should they become problematic. The aim of
this manual is to better inform farmers, directly or indirectly, of a number of the
more major pests and diseases that threaten coffee production in eastern
Africa and, as a consequence, to better empower them to take action as
and when required. The manual makes reference to ten pest and disease
constraints, selected for inclusion on the basis of those identified and
prioritized by participants
1 at a Coffee Research Network (CORNET) Regional
Coffee Stakeholders’ Workshop held in Nairobi in October, 2004. A summary
of the priorities emerging from this workshop is provided in Appendix 1. All of
the constraints identified at the workshop are covered. For each, the manual
provides a description to help with constraint diagnosis and identification of
the causal organism. Information is provided on their importance (e.g.
economic importance, coffee types af fected), geographic occurrence,
1 Participants were from eight countries (Burundi, DRC, Ethiopia, Kenya, Madagascar,
Rwanda, Tanzania and Uganda) and repr esented coffee farmers, processors,
marketers, regulatory bodies, policy makers, civil society and development agencies
5biology and ecology (including survival, spread and life cycle of the causal
organism) and on known approaches to management. These are supported
by photographic illustrations principally of the organisms and the symptoms
they induce on coffee. Detailed descriptions of the morphology of the
relevant fungal and insect organisms is also provided, although this is
intended more for the benefit of those who already have some knowledge
and experience of these aspects and who also have access to microscopes
and other equipment required to observe the organisms in detail. The manual
has been produced in a use friendly format and principally to meet the needs
of service providers, including agricultural extension. However, it may also be
suitable for direct consultation by some farmers.
Where possible, an integrated approach to pest and disease management
(IPM), involving use of a combination of cultural, biological and/or chemical
measures should be considered and followed. Such an approach has
advantages in terms of, for example: avoiding or minimising use of chemical
pesticides that are often costly and also damaging to other organisms, man
and the environment; promoting crop growth and vigour, thereby helping
plants to tolerate pest damage and fight off infections; and helping to
maintain biodiversity and utilise natural organisms against those organisms
responsible for pest and disease outbreaks. For each pest and disease
included in the manual, the various management measures known are
addressed in order to facilitate development of an IPM approach. Where
appropriate, control measures recommended in eastern Africa are
incorporated, along with measures applied elsewhere that may be
applicable to the region. Some information is also provided on possibilities for
management that may currently be under investigation but show some
promise.
Mike Rutherford
February 2006
6Part 2
COFFEE PESTS
7Coffee Berry Borer
IMPORTANCE
The beetle Hypothenemus hampei
is commonly referred to as the
Coffee Berry Borer (CBB), and is the
only serious pest of the coffee
bean in field grown coffee. This
beetle originated in Africa but has
now spread, through trade, to all of
the major coffee producing
countries of the world. It is now so
widespread and causes such
damage that it is widely
considered to be the most
important pest of coffee. In 1994/5,
for example, CBB infested 650,000
hectares of coffee in Colombia,
reduced national crop production
by 1.5 million bags and cost an
estimated US$ 100 million.
CBB is known to occur in Burundi,
Democratric Republic of Congo,
Ethiopia, Kenya, Malawi,
Mozambique, Rwanda, Sudan,
Uganda, Tanzania and Zimbabwe.
It attacks C. arabica grown at
lower altitudes, C. canephora and
forest coffee, and becomes less of
a problem in tropical areas above
1500 m.a.s.l. While c
offee is its
primary host, the pest
has been
known also to feed on the seeds
and berries of other plants,
including the pods of legumes.
Attack by CBB can result in
premature fall of berries and hence
total crop loss. In other cases the
berries may remain attached until
harvest but the beans are reduced
in weight, of lower quality and their
flavour is adversely affected. As
such, their commercial value is
reduced.
DESCRIPTION
The CBB is a small black beetle
about 2 mm in length and 1 mm wide. As the adult female bores
into the green coffee berries to lay
its eggs, occurrence of the pest
can be recognised by the
presence of small, round entrance
holes about 1 mm in diameter and
almost always close to the apex
(tip) of large green or ripened
berries. The female then bores a
short distance into a bean where
she lays her eggs and where the
young insects (larvae) develop.
Usually only one entrance hole is
present on a berry but, when
berries are scarce, several holes
may be made as a number of
females try to enter. They also bore
into the tissues of younger berries
but, finding them unsuitable for
breeding purposes (because the
endosperm is undeveloped) they
either wait there for some weeks or
they leave. A proportion of these
prematurely attacked berries will
rot due to bacteria and fungi
contaminating the berry through
the entrance hole. Mature beans
that have been damaged develop
a distinctive blue-green
discoloration and may contain
numerous small white and legless
larvae, the head of which is brown.
Larvae of the coffee berry borer,
H.
hampei, and damaged coffee
8bean.
Photo courtesy Jim Waller, CABI
As the eggs are laid over several
weeks, the larvae within any one
berry will be at various stages of
development (see ‘B
IOLOGY AND
ECOLOGY ’ below). Where
premature fall of coffee berries is
observed this may be due to
attack by CBB, but these losses are
often not attributed to CBB by the
farmer.
Side view of adult coffee berry borer. Photo courtesy Georg Goergen, IITA
Side view (scanning electron
micrograph) of adult coffee berry
borer. Photo courtesy Peter Baker ,
CABI
BIOLOGY AND ECOLOGY
The female bores into the
hardened and maturing coffee
bean where it lays about 30 whitish
eggs per berry over a period of
about 20 days. The eggs hatch 6 to
8 days later to produce the white
larvae. The larvae feed by
tunnelling through the tissues of the beans to create more spacious
areas (galleries) off the main
tunnel. Over a period of about
three weeks they pass through
either two (in the case of the male)
or three (in the case of the female)
stages of development (instars)
before pupating to become adults.
The period from egg laying to adult
takes between 25 and 35 days.
Some of the new generation of
borers will stay in the berry, mate
with each other and start the next
generation. When food resources
in the berry are becoming
exhausted the newly developed
adult females leave the berry and
fly from tree to tree to find a
suitable site to lay their eggs.
However, they wait for an
environmental trigger before
leaving the berry. The most
common trigger is rainfall – when
the berry is moistened by rain it
causes numerous females to leave
the following day during the late
morning and afternoon. High
temperatures will also cause the
adults to leave. The male beetles
do not fly and remain within the
berry where they fertilise other
females.
The adult female has been known
to live for long periods of up to 282
days, the male only 103 days. CBB
is therefore able to survive
between crops even where there is
only one crop per year. It usually
does this by staying in the berry in
which it developed until triggered
to leave. Infestations may be
maintained between peak
cropping periods by the insect
breeding in over-ripe berries
remaining on the tree or in those
that have fallen to the ground. This
has important implications with
regard to CBB control, as
described below. Low temperature
and low humidity limit survival of
9the beetle and its ability to breed,
and partly explain why CBB is less
problematic at higher altitudes.
M ANAGEMENT
Control of CBB has always been
difficult and costly. While cultural,
chemical or biological approaches
are suggested below, all have
drawbacks in terms of efficiency or
cost and no single approach
applied on its own is entirely
satisfactory. Combining two or
more approaches (e.g. cultural
practices and biological control),
as part of an integrated pest
management (IPM) package, may
have a greater impact and should
therefore be considered. Where
possible this combination should be
based on non-chemical measures
or minimising the use of chemicals.
Cultural methods, particularly
sanitation, prompt harvesting and
collection of mbuni from beneath
trees, should be given high priority
when control of CBB is being
considered.
Cultural control
As the CBB survives between
cropping periods in old dry berries
remaining on the tree and ground,
removal and destruction of these
(e.g. by burning or boiling) is one of
the most effective ways of
reducing beetle numbers and
hence controlling the pest. Berries
should not be left to dry on the tree
and any old berries should be
removed before a main flowering
to prevent carry over from one
crop to the next. It is especially
important to carry out this
sanitation practice before rains
arrive after a prolonged drought,
as in these conditions there may be
as many as 100 females per berry
waiting for rain to trigger their
dispersal. Mature berries should
also be harvested frequently and efficiently to minimise the number
remaining on the tree or falling to
the ground. If possible this should
be done every two weeks during
peak fruiting periods and monthly
at other times. A large piece of
material or mat may be placed on
the ground to collect berries that
fall during harvesting. Berries should
also be checked routinely and any
with small holes opened to verify
whether the bean has been
damaged or is discoloured, as this
indicates attack by CBB. Berries on
the lower branches and those that
have fallen on the ground are
more likely to be infested.
While these manual practices can
be beneficial they are laborious
and time consuming. If possible
farmers should try to determine
whether they are cost effective by
comparing crop yield and value
when they are practiced as
opposed to when plants are left
unchecked.
In some cases CBB is believed to
be more prevalent in damp or
shady conditions, but this will
depend on local conditions. This
pest tends to occur in patches and
those trying to control it should
spend time evaluating field
populations in relation to local
conditions. Once it is established
that certain areas are more prone
to attack, it can be recommended
to the farmer that special attention
be given to these areas.
Biological control
A number of important natural
enemies of the CBB, H. hampei, are
known to occur in Africa. Of these,
four parasitic wasps have been
investigated for biological control
purposes: Cephalonomia
stephanoderis, Heterospilus
coffeicola, Phymastichus coffea
10
