Integrated pest management in the Caribbean
by Don Walmsley
The answer to farmers' pest problems seemed to have been found
in the late 1940s and early 1950s when synthetic pesticides became available in
vast quantities in the industrialised countries of the world. In time these came
into general use in the Third World countries. Not only were farmers there
introduced to the new technologies through government extension services; they
were also enthusiastically encouraged to adopt these practices by the
representatives of the agro-chemical manufacturing companies - for obvious
reasons. Generally, farmers who could afford to buy them were impressed by their
obvious effectiveness in wiping out the pests and thus reducing crop losses.
Unfortunately, as is now well known, this happy state of affairs
did not last for very long. Soon insect pests developed resistance to the
chemicals with subsequent resurgence. The situation was made worse since often
the chemicals used not only destroyed the target pest but also its natural
enemies, thus upsetting the ecological balance in a negative way. The immediate
answer to this was to apply heavier doses and develop new active ingredients.
However, it soon became clear that this cyclic approach could not be maintained
successfully on an ongoing basis. A new strategy was needed.
Thus, in the 1960s other concepts were developed whereby a total
eradication of the target pests was not expected but rather that they be kept at
acceptable levels through a set of management practices which might, or might
not, include the use of chemical pesticides. This type of approach became known
first as integrated pest control (IPC) and later, as the concept developed, as
integrated pest management or IPM.
The Caribbean situation
Farmers in the Caribbean region, in common with those in other
developing countries, have been using chemical pesticides in ever increasing
quantities and, variety of products. They became familiar with the application
techniques and were encouraged in their efforts by the agro-chemical suppliers
and government agencies. Many governments, in their desire to assist
agricultural development, introduced subsidy schemes for agricultural inputs.
These often included pesticides, thus exacerbating the potential for their
In more recent times there has been the realisation that apart
from the more costly inputs, there were other prices to pay for the
indiscriminate use of these potentially dangerous agro-chemicals. These include
the health hazard, not only to the farmers themselves but also to the general
population, and the deterioration of the environment. There are also economic
considerations which cannot be ignored. Several Caribbean producers and
exporters of fresh fruits and vegetables have found out to their cost that
consumers in importing countries are not willing to tolerate chemical residues
in their foodstuffs and have a very strict monitoring system. Also there are
likely to be losses in the newly developing ecotourism business if potential
visitors have doubts about the quality of the local food and environment. Many
of the Caribbean countries depend heavily on agricultural exports and tourism in
their economy so in this context perhaps the proper question should be: can the
Caribbean countries afford not to reduce pesticide use and adopt the more
environmentally friendly IPM approach?
Major pest problems
Among the most serious pests in the Caribbean are the sweet
potato whitefly, (Bemisia tabaci) and Thrips pa/mi. These two pests are usually
found together and any strategy for their control has to deal with them as a
complex. Both are mainly pests of annual vegetable crops, both are virus
vectors, and both are believed to have assumed their present pest status as a
result of the insecticide regimes currently practiced.
Thrips palmi was first recorded in the Caribbean in 1985. It has
been estimated that its establishment on solanaceous and curcubitaceous crops
has contributed to trade reductions of over 90% in both Guadeloupe and Trinidad.
In addition, local markets can only offer smaller, deformed and scarred fruit.
During the mid-1980s a new strain of the sweet potato whitefly
(sometimes referred to as silverleaf whitefly) invaded the Caribbean and is now
devastating important root and vegetable crops. The diseases associated with
whitefly which predominate in the Caribbean are caused by geminiviruses.
Whiteflies and the diseases they transmit cause epidemics resulting in annual
losses costing millions of dollars.
Another cause of great concern is the citrus tristeza virus
(CTV). It was introduced with its vector, the brown citrus aphid (Toxoptera
citricidus), from South Africa into South America in the early part of the
century, causing havoc to the citrus industry in much of Argentina, Brazil and
Uruguay over the period between 1930 and 1960. More recently, outbreaks in
Venezuela in the early 1980s have devastated the industry there. Since then the
vector has been spreading steadily northwards and has been found in Central
America, reaching Nicaragua by the middle of 1993 - its arrival in Belize is
considered imminent. CTV has already been widely distributed in the Caribbean
through movement of budding, grafting and planting material. Trees with sweet
orange rootstocks are not severely affected but fruit on sour orange stocks is
very susceptible and these are still the most common in the Caribbean. Spread is
currently low because of the low transmission efficiency of the endemic vector
species and there is a preponderance of the mild strain of the virus. This
situation will change dramatically if no action is taken before the inevitable
arrival of Toxoptera citricidus.
Also of much concern to citrus growers in the region is the
damage done by various citrus root weevils - for example, in the Dominican
Republic Diaprepes abbreviatus is considered a major pest.
The seminar on IPM held in the Dominican Republic
It was within this scenario that for the recent (November 1993)
CTA/ CARDI ninth annual Caribbean seminar the topic chosen was IPM: A
Comprehensive Strategy for the Caribbean Farmer. The meeting was held in Santo
Domingo, the capital of the Dominican Republic, one of the most recent countries
to attain membership of the ACP-EU grouping. The seminar was jointly organised
by CTA, the Caribbean Agricultural Research and Development Institute (CARDI),
the Secretaria de Estado de Agricultura and its Departmento de Investigaciones
Agropecuarias (SEA/DIA), the Fundacion de Desarrollo Agropecuario Inc. (FDA),
the Junta Agroempresarial Dominicana Inc. (JAD), and the local office of the
Instituto Interamericano de Cooperacion pare la Agricultura (IICA).
The theme was particularly appropriate for the Dominican
Republic since the once thriving tomato industry has recently suffered severe
losses as a result of whitefly infestation, and the citrus industry is severely
affected by root weevils and under threat from CTV and its vector, Toxoptera
citricidus. Indeed, the subject of the meeting was considered of such importance
there that the Secretary for Agriculture, Victor Hugo Hernez, not only
formally opened the seminar but also participated in the closing session.
The technical papers presented by scientists - from the region
and other parts of the world - revealed that one of the main constraints
introducing the IPM approach was the difficulty in persuading farmers of its
value and long-term effectiveness. They were used to applying pesticides and
seeing their obvious and immediate results. Therefore one of the main tasks
would be to educate farmers as to the advantages of reducing pesticide use and
adopting the more sustainable management practices now advocated.
In this respect, it was suggested at the meeting that a
successful model which could be adapted to dealing with serious pest problems in
the Caribbean was that developed under a FAO programme on rice in south-east
Asia. In that part of the world problems arose because the new, improved rice
variety which had been planted over very large areas was found to be susceptible
to the rice brown planthopper, previously only reported to be a pest of rice
grown in temperate countries. The pest quickly developed resistance to
insecticides and its other characteristics, along with the destruction of its
natural enemies, led to outbreaks of epidemic proportions. Research into the
whole pest complex and ecology of the system eventually came up with the
recommendation that the use of pesticides should be discontinued. The problem
now was to get this message across to the extension agencies and, most
importantly, the farmers. A massive IPM programme was mounted to sensitise
farmers to the role of natural enemies in pest regulation. This was based on
'IPM Farmers Field Schools', which is a new methodology entailing a continuing
close collaboration between researchers, extension workers and farmers. The
method involves elements of infield training and hands-on experience.
Eventually, farmers can decide what action to take themselves without having to
seek advice from others. Part of the strategy is that farmers train other
farmers. Three basic principles followed by the farmers are: grow a healthy
crop; conserve beneficial organisms such as pest predators and parasites; and
observe fields regularly to determine the management actions necessary to
produce a profitable crop.
The components of an appropriate pest management regime could
include: resistant plant varieties; biological control (predators, parasites,
pathogens, 'biopesticides'); crop sanitation (burning residues, closed season);
mechanical methods (colour traps, mulches); cultural practices (crop rotation,
cropping mix, overhead irrigation); pheromone technology; judicious use of
selective, less deleterious chemicals (including natural products and insect
growth regulators) along with efficient spray application techniques; plant
Research on most if not all of these elements was reported from
several countries in the Caribbean but seldom had it been possible to offer
farmers a complete package of IPM practices tailored to their own particular
circumstances. Some examples of the use of such components are discussed below.
Farmers in Barbados have become more selective in their use of
insecticides and now also include insect growth regulators. In Trinidad a range
of indigenous natural enemies of Thrips palmi have been recorded, including
predatory mites, anthocorid bugs and fungi, and research is now aimed at mass
production of these for field application. A promising fungus species for
control of both whitefly and T. palmi was found to be Paecilomyces fumosoroseus.
This pathogen, which also infects diamond-back moth, is being fieldtested in
aqueous and oil-based formulations. In the hope of containing whitefly and
associated viral diseases, the Dominican Republic has enacted laws and
regulations to enforce a closed season and to regulate planting of whitefly host
crops in selected regions. Other components of alternate management strategies
to conventional pesticide use tried there include intercropping vegetables with
sorghum, use of neem extracts and insect growth regulators, and resistant tomato
varieties. In Honduras, several types of control methods (mechanical, cultural
and chemical) for geminiviruses in tomato and chile peppers have been
investigated. The most effective were protected nurseries, optimal cultivation
practices, and efficient insecticides. In the Dominican Republic the fungus
Beauveria bassiana and the insect Tetrastichus haitiensis are being
mass-produced for use in the fight against the citrus root weevil, Diaprepes
In response to the threat to the citrus industry posed by the
severe strains of tristeza along with its very efficient transmission by T.
citricidus, most countries (including Trinidad, Belize, Martinique and
Guadeloupe) are changing the susceptible sour orange rootstock used in their
citrus nurseries to more resistant varieties (which should also be tolerant to
other major diseases) and persuading farmers to plant them as a matter of
urgency. The bud wood used must be certified free of transmittable diseases.
Eradication of trees with severe CTV strains is another important but unpopular
measure Cross protection techniques using mild strains of CTV are also being
considered. More stringent quarantine controls are being put into effect.
On the field excursion, seminar participants were able to see at
first hand the way in which farmers in the Dominican Republic were adopting IPM
technology. By using these measures, vegetable farmers in the Valle de Constanza
have been able to reduce the number of spray applications, for example, from
9-12 to 3-5 for a cabbage crop, and from 10-12 to 4-5 for tomato; sweet potato
spraying has been cut out altogether from a previous 23 sprays per crop. It is
implicit in this that some monitoring mechanism of the pest population be
established in order to give guidelines on when it would be necessary to apply
chemical pesticides. Here, farmers were using pheromone and colour traps to
assist in the monitoring process. However, the difficulty of getting over to
farmers that the chemicals they were using posed a health hazard was clearly
demonstrated; farmers were spraying without safety equipment and children were
It was interesting to note that a pesticide manufacturer was
actively assisting in this programme - the attitude being that in the future
only pesticides compatible with the IPM concept would be acceptable.
The participants devided into four working groups to discuss:
IPM for vegetable crops; IPM for citrus; IPM for small-scale farmers in mixed
systems; institutional methods to promote IPM. The main conclusions and
recommendations may be summarised as follows:
· Policy-makers in the region
should be made aware of the concept and importance of IPM to agricultural
development consistent with a healthy and stable environment
· Noting that the International
Pest Management Working Group intends to launch a Latin American and Caribbean
sub-group at its 1994 meeting in Costa Rica, steps should be taken to have the
recommendations arising from this present meeting placed before the sub-group
for endorsement. Also steps should be taken to establish a Caribbean chapter of
the subgroup with its own newsletter.
For citrus, the status of proposals for international and
regional cooperation (FAO and IACNET) needs to be clarified. The conclusions of
this meeting will be presented at a CTV workshop in Mexico at which
international cooperation and funding will be considered. It is essential that a
system of regional cooperation in transfer of information, budwood and
technology be established. The offer of safe citrus germplasm transfer to the
region through Martinique by the French Inter-ministerial Fund for Regional
Cooperation, with approval from the International Board for Plant Genetic
Resources, was noted.
· There is an urgent need for
the education/training of farmers and extension workers to bring about a change
in attitude and to give them the required knowledge in the appropriate use of
recognised IPM components in local farming systems. This would involve working
with farmers and farmer organisations using succesfful models developed
elsewhere and adapted to Caribbean conditions.
· A group should be set up with
responsibility for producing hand-outs/factsheets on the several approaches
recognised at the meeting for the control of Bemisia, thrips, tristeza and
Diaprepes. These should be addressed to farmers, extension workers and
researchers and be made available in the three main languages of the Caribbean -
Spanish, English and French. The support of CTA, CABI etc. for this exercise
should be sought
· A study of economic losses
incurred in the region due to pest damage is needed along with the establishment
of economic thresholds.
· An inventor of the regional
physical and human resources available for IPM should be developed along with a
database on all aspects of IPM.
· Plant quarantine should be
strengthened (possibly with the assistance of FAO).
· Increased control of pesticide
use should be implemented through updating legislation and regulations at the
· Coordination of research
activities is needed among universities, government institutions and other
research organisations. Networks for research and information should be
established with links to international groups.
· Although there is a need for
support from the international donor group, it is very important that budgeter
support is provided at the national and regional levels. D.W.
The author is indebted for background material to papers read at
the seminar by T J Perfect and J C van