Challenges to the Plant Health System in St Kitts and Nevis
Lilory D. McComie, PhD.
Introduction
Increased production of high-valued non-traditional crops such as tropical fruits and vegetables and the development of a viable tourism sector have impacted on trade in agricultural produce in St Kitts and Nevis. Local produce is exported to earn foreign exchange and various commodities are imported regularly to satisfy overall consumption demands. Trade involving the movement of plant material is conducted in a liberalized environment with certain attendant risks, particularly that of accidental introduction of exotic plant pests and diseases.
Pest introductions to St Kitts and Nevis
Within the last ten to fifteen years, St Kitts and Nevis as the rest of the region have experienced the introduction of a number of new pests and diseases of economic importance. Pest introductions probably far exceeded diseases because of the ease with which insects can be concealed and transported on plant material. Pest introductions included the palm thrips Thrips palmi, sweet potato whitefly Bemisia tabaci, the pink hibiscus mealybug Maconellicoccus hirsutus, (HMB) the citrus blackfly Aleurocanthus woglomi, the citrus leafminer Phyllocnistis citrella, and the papaya mealybug Paracoccus marginatus. The most notable disease introduction was the bacterial canker, Erwinia sp. of papaya. Much earlier pest introductions such as the diamondback moth Plutella xylostella, the coconut scales Aspidiotus destructor, coconut whitefly, Aleurodicus cocois, the mango fruitfly Anastrepha obliqua and the West Indian Canefly Saccharosydne saccharivora continue to be the bane of agriculture on the islands. Other extra regional pests such as the mango seed weevil Sternochetus mangiferae, and the giant african snail Achatina fulica are present in neighbouring islands (FAO, 1989a) but not in St Kitts and Nevis, and are a constant threat to the islands. Similarly there are diseases in neighbouring countries that pose serious threats such as black sigatoka, Mycosphaerella fijiensis in Jamaica and Venezuela, bacterial canker Xanthomonas campestris p.v. citri of citrus in Florida (Vokarty and De Chi, 2000) and Anthurium bacterial blight Xanthomonas campestris diffenbachiae in Jamaica, French West Indies (FAO, 1989b) and Trinidad.
Origin of exotic pests and diseases
Many of these extra regional pests originated from Asia e.g. the hibiscus mealybug, palm thrips, mango seed weevil, and citrus mealybug. The papaya mealybug is from Central America. This shows that in addition to threat from pests that alien to the region, there are also threats from New World pests, which now have limited distribution in some islands and/or the mainland. There are many species of mealybugs and related insects that could go undetected as they remain concealed and can be easily transported unnoticed on plant materials (Watson and Chandler, 1999). Other serious pests such as the coffee berry borer Hypothenemus hampei in Jamaica may be of no consequence as St Kitts and Nevis do not grow coffee. FAO (1989b) lists the distribution of a number of other regional and extra-regional pests and diseases of quarantine importance that are potential threats to the islands. While the document needs to be updated it still remains a useful reference manual for the entire region.
Some of these new introductions are host specific, e.g. the mango seed weevil, while other are limited to a few plant families, e.g. the diamondback moth is a pest of cruciferae - cabbage, cauliflower, broccolli. Yet there are those which pose a threat to a number of plant species because of their wide host range. The pink hibiscus mealybug belongs to this category and such pests spread very rapidly when introduced without their natural enemies.
One could never always be sure of the means by which new pests and diseases are introduced, but in the Caribbean a number of avenues for inadvertent introductions have been recognized as follows:
Economic impact of new pest and disease introductions
New pest and disease introductions could be extremely damaging and may have serious economic consequences in terms of loss of production, cost of sustained management and loss of export market. At the macro-level this could affect national development through the loss of valuable foreign exchange earnings and the diversion of resources to alleviate the problems. Other socio-economic impact could be poor income generation due to poor production at the farm-level. Economic activity in the agricultural sector was affected to some degree in St Kitts and Nevis upon introduction of the hibiscus mealybug in 1995. By 1996 neighbouring islands placed trade restrictions on produce from infested countries, and St Kitts lost a once viable export market for onions even though onion was not a host of the mealybug. The export trade never recovered and this was a major factor in the decline of onion production in St Kits and Nevis from 238 tons, i.e. 476,000 kg in 1996 (CARDI, 1999), to 64,272 kg in 1999 (DOA, St Kitts and Nevis). Even to resume trade would entail certain overhead costs in order to meet protocols and standards stipulated by importing countries. It would be necessary to establish a centralized cleaning, treatment and clearing facility as well as meet certain requirements for packaging and transportation (Chandler and Hunte, 2000).
Eradication or management of these pests and diseases is often conceivable, but may be difficult, costly and time consuming. Pesticides are still widely used to control many pests such as the diamond back moth. But no longer can we continue to rely heavily on pesticides since they are expensive and insects build up resistance relatively quickly. The quantity of pesticides imported annually for agricultural use in St Kitts and Nevis between 1993 and 1999 was over 2.5 thousand kilograms, at a cost of between EC$2.7m and 4.0m (see Table 1). Pesticides are also damaging to the environment and can upset delicate ecological balance particularly in fragile island ecosystems. Therefore whatever pest management strategies are put in place must minimize pesticide use.
Table 1 Imports of pesticide into St Kitts and Nevis for agricultural use between 1993 and 19991
|
Year |
Quantity (kg) |
CIF value ($EC) |
|
1993 |
257,518 |
2,729,788 |
|
1994 |
272,731 |
3,243,162 |
|
1995 |
303,574 |
4,008,405 |
|
1996 |
321,156 |
4,035,602 |
|
1997 |
251,975 |
2,862,757 |
|
1998 |
284,756 |
3,727,391 |
|
1999 |
397,066 |
2,871,706 |
1Source: Planning Unit Ministry of Finance, Development, Finance and National Security, St Kitts Office.
A more practical approach is integrated pest management inclusive of biological control. St Kitts and Nevis has a long history of natural enemy introductions for pest management, dating as far back as 1932-1934 when the tachinid parasite Lixophaga diatraeae was introduced to control the sugarcane stem borer Diatrea saccharalis (Cock, 1984). Natural enemies were introduced in the 1960s to 1980s to control a number of pests including the diamond back moth, army worms Spodoptera spp., West Indian fruitfly, cottony cushion scale Icerya purchasi and others (SSMC, unpublished reports). In most cases there were no follow-up programmes to determine the level of successful long-term establishment of most of the introduced biocontrol agents. Regular monitoring by SSMC, however, shows that the sugarcane stem borer is still being kept below economic thresholds by the two introduced parasites Lixophaga diatraeae and Cortesia flavipes (Carol Henry, pers. comm.). Perhaps the most successful biological control programme with the greatest impact on St Kitts and Nevis was developed for management of the pink hibiscus mealybug. Four natural enemies were introduced under this programme as follows: the predatory beetles Cryptolaemus montrouzieri and Scymnus coccivora and the parasitoid wasps Anagyrus kamali and Gyranusoidea indica.
Although biological control may be sustainable there are attendant costs, and follow-up action is imperative. One hundred and fifty thousand (150,000) predatory beetles, Cryptolaemus montrouzieri, were purchased at the cost of EC$0.27 per beetle for introduction to St Kitts between 1996 and 1998. The cost the HMB management programme in St Kitts, inclusive of biological and chemical control during the same period, was over EC$1.3 million dollars (DOA, St Kitts). After spending over EC$500,000.00 on eradication/management, the mango fruitfly is still well established on the island and farmers lose some of their mango crop to pest every year (DOA, St Kitts). The natural multiplication and distribution of biological control agents for HMB was augmented by additional importation, laboratory rearing, relay releases and field monitoring. Some of the latter is still going on, though at a much lower level than at the height of the programme.
Other quarantine pests, such as the mango seed weevil, are difficult to manage and trade in fresh mango is generally encouraged between countries which have the pests. The citrus canker is a highly contagious, incurable disease for which there is known no control (Vokarty and De Chi, 2000). This disease should be kept out of the Federation since it could seriously threaten the fledgling citrus industry. The severity of plant damage may be greatly diminished when pests are introduced with their natural enemies, as with the introduction of M. hirsutus to Guyana (Munroe, pers. comm.) and Hawaii (Beardsley, 1985), but such examples are few. In both cases the encyrtid parasitic wasp Anagyrus kamali was introduced at the same time as the mealybug. It is also possible that indigenous natural enemies may attack new pests, as in the case of the papaya mealybug where up to 38% parasitism was recorded in St Kitts and 23% in Nevis. Very often, however, extensive plant damage may occur before the problem is brought under control.
In most cases biological control or overall management of exotic pests must be done in collaboration with regional and international agencies. The successful management of the hibiscus mealybug was instructive and a good example of how collaboration among such agencies can be complimentary in bringing about quick and effective management exotic pests. The primary agencies that collaborated in this effort were CARDI, IICA, FAO and USDA.
Mechanisms to minimize the risks of new pest introductions
Because of the potentially far-reaching socio-economic impact of such exotic pest and disease introductions every effort must be made to exclude them. It would be a serious challenge to keep out exotic pests or diseases that may have entered any one country of the region because of our traditional easy going and informal relationships. The free and easy trading relationships, free movement of vessels and people, lax security of our borders and coastlines and the now liberalized trading environment present many difficulties. Nevertheless, various approaches to alleviate this problem should be given consideration. Among the most important are policy, strengthening of plant quarantine, pest risk analysis, public awareness, training and development of a contingency plan with integrated pest management as a main component. Regard must be paid to the epidimiology and bionomics in attempting to optimize management strategies.
It has been generally accepted that the region’s agricultural health services, must promote effective trade in the 21st century whilst protecting the agricultural sector and indigenous plant life from introduction of exotic pest and diseases of economic importance. In this regard St Kitts and Nevis must subscribe and adhere to international guidelines, codes of conduct and phytosanitary measures, which govern international trading agreements. Furthermore the Federation must comply with the sanitary and phytosanitary measures of the World Trade Organization and Free Trade Agreements such as the Free Trade Agreement of the America’s (CARICOM Secretariat, 1999). The islands must also be prepared to actively participate in negotiations or ensure that their views are adequately represented on phytosanitary matters on the world arena.
It has also been recognized that Plant Quarantine is the first line of defence against introduction of exotic plant pests and diseases and that plant quarantine laws should be strengthened to reflect this. Plant protection legislation, which governs plant quarantine in many of the islands, dates back to the 1940’s or before, when such threats were remote. To be effective therefore, the Laws and Regulations must be upgraded to enable strict enforcement throughout the region. All the islands of the OECS recognize this need, but some including St Kitts and Nevis have been tardy in implementing recommendations from international organizations such as those provided by FAO (Bombín, 1993). Meanwhile temporary regulations continue to be drafted to handle each new pest situation. A recent example is the ban on entry of fresh mangoes from mango seed weevil infested countries of the region. The challenge here is not in accepting recommendations for upgrading Plant Protection Laws but in accelerating a response.
Pest risk analysis should be prioritized and routinely conducted to determine the risk levels and pathways by which new pests and diseases may enter the islands. Once these pathways are defined, quarantine inspection should be intensified to detect and prevent undesirable entries. Good risk management may not always prevent but may delay the entry and establishment of new pests and diseases. Training in the risk analysis process is essential for any such exercise to be successful.
Public awareness programmes via the media – radio, television, newspapers, posters and leaflets, can effectively in impress on residents their responsibility for observing plant quarantine laws and regulations. This could help to prevent the unwitting entry and spread of exotic pests and diseases before competent authorities recognize them and take appropriate action. The advent of the hibiscus mealybug provided a novel opportunity to disseminate information and elicit public support and participation in management of a pest. Not only was the campaign successful, but it was a valuable learning experience that provided a model on which to develop similar public awareness programmes in the future. People need to be constantly reminded of their responsibility in helping to keep out unwanted pests and diseases.
The importance of an emergency action (preparedness) plan for exotic plant pests and diseases has been well-articulated (Berg, 1986; Ambrose, 1996). Such an action plan should clearly outline action to be taken, personnel to be involved and assign responsibility at each stage/level of the programme. Ambrose (1996) developed "A model action plan for Caribbean countries" that should be critically reviewed, modified and adapted to suit each territory.
Surveys and surveillance should be conducted regularly to monitor and determine the pest and disease status on each island. Extreme vigilance must also be kept at all ports of entry i.e. airports and seaports in St Kitts and Nevis. Surveys may be general or specific and may be conducted quarterly, annually or seasonally. They may target specific pests e.g. fruit flies, mango seed weevil or specific crops. The resulting information should be used to update pest and disease checklists. Staff must be trained in pest and disease identification particularly those of quarantine and economic importance, as well as survey techniques, for such an exercise to yield meaningful results. This would greatly increase the chances of early detection of exotic pests and reduce the impact of such introductions.
Summary and conclusions
The challenges to the Plant Health System may be met by:
Acknowledgements
I wish to acknowledge the assistance of Dr Jerome Thomas, the Director of Agriculture, St Kitts and Mr Augustine Merchant, Director of Agriculture, Nevis in providing some valuable information used in this paper. Mr Antonio Francis of the Department of Agriculture, St Kitts, provided valuable insights through our many discussions. The Planning Unit of the Ministry of Finance, Development, Planning and National Security provided statistics on pesticide imports. Ms Carol Henry of SSMC also provided a historical perspective and other useful information on early introductions of biological control agents into St Kitts and Nevis.
References
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Berg G H. 1996. Pathway risk Analysis of Maconellicoccus hirsutus (Green) pink mealybug at the Global Level. OIRSA, San Salvador, El Salvador.
Bombím L.M. 1993. Report to the Government of Saint Kitts and Nevis on Plant Protection Legislation. FAO Technical Co-operation Programme TCP/STK/0051(A). Unpublished Technical Report. FAO, Rome.
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FAO. 1989a. FAO/RLAC plant quarantine Action programme (1) Data Sheet on Mango Seed Weevil (2) Survey Protocol for Mango Seed Weevil Detection (3) Data Sheet on the Giant African Snail. RLAC/89/08- PROVEG-19, Santiago, Chile.
FAO. 1989b. FAO/RLAC Plant Quarantine Action Programme. Pests of Quarantine Importance to the Caribbean. RLAC/89/19. Santiago, Chile
Vokarty S. and De Chi W. 2000. Citrus canker in Florida. CARIPHIN News 19:9.
Watson G. W. and Chandler L.R. 1999. Identification of mealybugs important to the Caribbean region. Commonwealth Science Council and CAB International, London.
URL http://www.uwichill.edu.bb/bnccde/sk&n/conference/papers/LDMcComie.html
© Lilory D. McComie, 2000. HTML prepared using 1st Page 2000, revised by author July 6th, 2000, last editorial revision September 29th, 2000.