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The Bio-security Threat Due to International Trade of Plants, Wood and Plants Parts

Title of Term Paper:

“The bio-security threat due to international trade of plants, wood and plants parts”



Introduction ……………………………………………………………………………………4

Discussions and Literature reviews……………………………………………………………………………..1.0

International Plant Biosecurity and the Organizations involved………………………………………1.1

International trade of wood and plants products…………………………………………….1.1.1

Modern plant trade as a regulator of threat enhancement…………………………………….2.0

Pests associated with wood, plants and plants parts…………………………………………..2.1

Forest pests introduced through International trading……………………………………….2.1.1

Impact due to international trade of woody parts and plant parts…………………………….3.0

Risk analysis…………………………………………………………………………………..3.1

Measures to minimize the risk of introduction ………………………………………………3.1.1

Discussions and Conclusions………………………………………………………………….4.0



International trade in wood, plants parts, and live plants for planting has been known worldwide as one of the major pathways for the introduction and spread of non-native or foreign pests and plant pathogens.  Non-native species in new areas can become invasive species. These organisms upon arrival in their new environment may cause devasting ecosystem and economic damage to both host plants, human and even alternative host plants as well.  This can also limit access to international exports markets. Despite, all the regulations at the borders by the various government agencies, the introduction of foreign pests to new areas is still inevitable. Introduction of pest and pathogen to countries such as the United State of American, Europe, Canada and South African have been documented over the years. Trading among diverse countries’ thus importing and exporting of plants products, has led to the increases in widespread of plants diseases in recent times, despite its obvious economic advantage. The potential for damage in the future might be large if tight measures are not put in place to address international trade market and biosecurity threat to plant health. Therefore, this paper provides a review of how wood and plant parts commodities has attributed to biosecurity threat through international trade, the major entry pathways and measures to minimize the risk associated with international trading in wood and plant parts commodities.


The term biosecurity broadly encompasses the efforts to avoid damage from both deliberate and accidental movement of organisms to human well-being and the environment, as well as to the agricultural crop and livestock industries. Plant biosecurity is a technique and integrated approach designed towards the management of potential risks in the areas of food safety, and plant life and health, including associated environmental risk (Meyerson and Reaser 2002a).  It also consists of activities such as quarantine measures, before and after border inspections, off-shore mitigation, domestic surveys and eradication and control programs (Magarey et al.,2009). Conventionally, biosecurity programmes concerning plant health have focussed on pests of the agriculture and forestry sectors.  However, in recent years numerous efforts have broadened and ensured that scope of plant health biosecurity policy to also tackle plants as a pest, or invasive plants, and spreading protection to non-agricultural or unmanaged systems.

         Pest and pathogens may adhere to invasive plants surface of wood and plants parts, which pose a threat to croplands, rangelands, and natural areas.  Invasive species are referred to as exotic species with maximum potential proliferation rate and dispersal that becomes predominates components of ecological communities (Colautti and  MacIsaac, 2004). They cause degradation of the productivity and biological variability of all ecosystems, have harmful economic and social impact and affect international trade. Their impact and influence have increased rapidly over the past years because of increased exports and imports into new international markets, the increased frequency and speed at which commodities and people travel the world, increased numbers of ports of entry, increased interest in the use of new exotic plants for gardening and landscaping (Mullin et al., 2000).  This elevated level of damage by invasive plants has challenged plant health biosecurity organizations, to come up with new programmes and measures to protect the economy, environment, and human health (Hewitt et al., 2009).

          Comprehensive studies have already confirmed that movement of wood including solid-wood packaging and the ornamental plant trade as the two main pest pathways. There is a positive correlation between the pest introduced via this route and the volume of the source of imports. Hence, there is the need to develop measures in the regulation of the movement of wood and plants parts that lead to a reduction in pest entry via this  pathways, most especially on international trade markets. This paper examines biosecurity threat from international trade of plants, wood and plants parts, the main source of entry and measures to reduce the risk.

1. Discussions and Literature reviews

1.1 International Plant Biosecurity and organizations involved

International trade due to rapid globalization of the world economy suggests that trade policies and agreements need to be well considered by countries participating in the trade. Relative to agricultural trade, several international agreements, and standards to which many countries of the world are parties has been established. Those specifically associated with plants and plant products, are the WTO-SPS Agreement, the International Plant Protection Convention (IPPC) and the International Standards for Phytosanitary Measures (ISPMs).

The World Trade Organization (WTO) was established in 1995; with its key responsibility of trade liberation by limiting tariff and non-tariff barriers (Brunel et al., 2009).  It a body that sets and oversees the global rules of trade between nations. However, trade liberalization rather turns to increase the biosecurity risk. The WTO administers a set of agreements that are negotiated, signed and approved by governments of member countries. These agreements are legal rules that have implications for plant health biosecurity (WTO, 1995, 2011).   These agreements include the WTO’s General Agreement on Trade in Services (GATS) permits countries to take procedures to protect human, animal or plant life, and this may include measures to avoid the introductions of invasive pests. The WTO Agreement on the Application of Sanitary and Phytosanitary Measures (SPS Agreement) deliberates on how these measures may be put to effective use. The SPS Agreement allows counties to set their own plant health standards, however, it requires that these must be based on a systematically reasonable and suitable risk assessment (Roberts and Roberts, 1998; Shine, 2007).

The General Agreement on Tariffs and Trade was replaced by the SPS Agreement (Gruszczynski, 2006). The SPS Agreement sets rules for the growth of international standards and guiding principle and it recognizes the International Plant Protection Convention (IPPC) as the only suitable international standard-setting organization regarding plant health biosecurity (Gruszczynski, 2006). The main aim of SPS Agreement ensures that worldwide commercial trade in plant products is not obstructed by artificial barriers and is based on international standards (C. M. Brasier, 2008).  While WTO member countries have the sovereign right to protect their territory from potential threats of pest introduction, their measures must be based on the general principles of the WTO SPS Agreement. Under the WTO-SPS Agreement, 14 Articles or principles guide the application of SPS measures (WTO, 1995).

1.1.1 International trade of wood and plants products

Several forest products make up this trade.  Wood Global trade in wood products and plants parts for planting conveys the threat of introducing foreign tree pests and diseases (Liebhold et al., 2012), which can cause devastating ecosystem and economic damage. Even though international phytosanitary guidelines exist to help countries that import wood products, develop import standard to reduce pest movement.  The movement of these pests is still unavoidable.  A report from (FAO 2016), indicated that there has been a massive increase in the international trade in wood products currently than the past 50 years, from about 5 billion $US in 1961 to 248 billion $US in 2014 (Fig 1.). This contributed to about 1.7 trillion $US in 2014, as the total international exports of agricultural produce (FAO 2016).

       Wood commodities in the global markets include log and round wood.  Round wood comprises the largest percentage of international wood trade, which includes both industrial roundwood and fuelwood. Others include sawn wood and wood chips. All the wood products may possibly have pests associated with them (FAO 2016). With such significant increases in wood trade, forest pest risk threats resulting from trade volumes and the diversity of trading partners is definitely going to be on the increase. This allows for the movement of new forest pest in a new environment with possible damaging effects.

        Wood-feeding insects usually come with wood packaging material (WPM), which includes items such as pallets, crates, and dunnage (wood used to brace cargo). Packaging for foreign shipments of plants parts are normally built from wood because it’s inexpensive, most abundant, renewable, and easily constructed and easily repairable. Unfortunately, these wood used for the WPM construction might be infested with a wide range of diverse bark and wood pests and thus serve as a channel for pest movement. Wood-feeding insects can also be carried in fuelwood, live plants, logs, lumber, and various manufactured wood items   (Liebhold et al., Britton, 2012).

        The increased transport of woody ornamentals parts because of their aesthetic values has also attributed to the increase in biosecurity threat. Woody ornamentals are possibly able to harbor forest pest and the rate of pest development may rise when especially planted outside and close to other alternative live host (Smith et al., 2007). It was estimated that during 1996 to 2009, an average of 105 million live trees and shrubs were imported to the United State of American. Also,  between 2005 and 2009, approximately 135 million plants on average were imported yearly with soil or potting media attached to roots, which increases the risk of moving soil‐borne insects and pathogens, with 94% of such plant shipments originating in Canada (Liebhold et al., 2012). .1. The graph represents the international value forest product exports from 1961–2014

Adapted from (FAO 2016).

2.0 Modern plant trade as a regulator of threat enhancement

Previously the international trade in rooted planting stock was limited, usually including small quantities for local production. While in recent times, international shipments of nursery stock and cut flowers are on the increase in most horticultural industries.  A considerable amount of planting materials sold in the UK nurseries and other plants wholesale outlets is now directly introduced from elsewhere. The movement of ‘Certificated’ plants from countries such as China, Japan, Australasia, and Africa to the UK and Europe are now predominate in global markets increasing the establishment of new pest and pathogen from these regions into the UK.

The supply of cheap plants parts from nursery cultivation centers in developing parts of Europe to other regions has also attributed to the movement of many infested exotic and endemic pathogens (Jock et al.,2002).  Propagation of such planting materials usually leads to disease developments. Infested nurseries in Europe and other areas with diverse species of close ancestry serves as breeding grounds of new traits and develop host range not known to the parent species ( Brasier et al.,2000).

Instant woody landscapes have also contributed to the movement of pathogens. The crown and stems of trees may harbor hidden pathogens or pests. The soil around the root can contain organism of different kinds. Some plants many escape the quarantine and microbial analysis process. An example is the hybrid alder Phytophthora transported with Alder saplings to Europe through to the UK for landscape and shelterbelts purpose (Gibbs, 2003b).

2.1. Pests associated with wood, plants and plants parts

Trees have been used as natural homes for a wide range of organisms, including insects, fungi, nematodes, and bacteria. Many of these organisms do not pose a serious harm to tree health or wood quality. However, their movements and development in new countries may have a devasting ecosystem effect (Kenis et al., 2009).  Those considered as pest may cause a detrimental impact on tree health or wood quality.  They are usually associated with plants parts such as root, stems, branches, and foliage.  While some may be found on the bark or wood tissues (Kenis et al., 2009).Most pest life cycle stages in wood are located in the bark, sapwood, and heartwood. The life cycle of bark beetle is found in the bark or in the phloem tissues just beneath the bark.  Therefore, elimination of the bark eventually exposes the inhabited organisms to unfavorable conditions that inhibit their survival. Such mitigation is effective not only for bark beetle taxa but also for other groups of organisms whose feeding or propagative behaviors constrain them to the bark and phloem tissues   (Haack and Slansky, 1987).   Log debarking is also crucial in the possible risk in the sense that some residual bark and wood-invading insects will lay eggs and develop successfully in various wood products  ( Haack and Petrice, 2009).

Organisms that depend on insect vectors for spreading might also be capable of establishing and disperse even when their vector is absent, though in some products the probability can be very minimal. For instance, the pinewood nematode, Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle), might be present in sawn wood either with or without its insect vector (Akbulut and Stamps, 2012). Nematodes and its vector have a complicated relationship, hence the probability of nematode transmission from inside the sawn wood to living trees in the absence of the vector is really low (Sathyapala, 2004). But in the case of coniferous wood chips infested with the nematode, a pathway for non-vector transfer to trees has been reported  (Hopf et al., 2017).

2.1.1 Forest pests introduced through  international trading

Comprehensive studies by researchers have indicated that the importation of plants parts, wood, and or live plants is traditionally the most common pathway for the introduction of non-native forest insect pests and pathogens to new environments. A report by the FAO 2016, showed plant imports in the US increased 33% per decade over the past years with 3.1% representing the horticulture industry  (Liebhold et al., 2012).An example of how species were transported into new regions, was demonstrated through a survey conducted by an entomologist traveling from  Trinidad to  Manila. The entomologist detected 41 species of insect including the invasive red flour beetle (Tribolium castaneum) also called the flour and grain pest. The insect come out of his suitcase when he unloaded his stuff in his new destination (Hulme, 2009). Here are few examples of pest and pathogen that has been transmitted via plants parts, wood and live plants.

In 1909, the white pine blister rust was detected on white pine seedlings exported from a German nursery to the Midwestern parts of US in 226 regions. The pathogen was also found on diseased eastern white pine seedlings transported from France nursery, some were located close to Vancouver and British Columbia (Spaulding,1911). The pathogen was responsible for pine cankers disease and increased the mortality of healthy plants of up to 90% in Western American (Merrill 1988).

The Sudden oak death (Phytophthora ramorum) appeared in the US as a forest pathogen responsible for the oak death. It was also found in California and Europe in the same year and emerged as a nursery pathogen  (Ivors et al., 2006). In Europe, the pathogen has disseminated to woodlands in countries such as the UK, Norway, the Netherlands, and Germany, and has been detected in nurseries of 16 other European countries and Canada  (Mascheretti et al.,2008).

In 2001, Citrus longhorned beetle (Anoplophora chinensis) was first found in Washington State nursery in the US (USDA 2010). An immediate control measure through eradication program was put in place to avoid the dispersal of the next generation of beetles.This was achieved by deforestation of about thousand trees, and a quarantine on the movement of wood was also ensured. This program was efficient in avoiding subsequent spread and colonization of the pathogen in 2001-2007 (Haack et al., 2010). Closely related species known as the Asian long-horned beetle ( Anoplophora glabripennis) is found with wood packaging materials which indicates the major pathway for invasion. Citrus longhorned beetle accompanied with plants materials was unintentionally introduced in Europe and in northern Italy (Haack et al., 2010).

3.0 Impact  due to international trade of wood and plants parts

Non- native plants pathogen and insects pose one of the economic threats on ecosystems. International trade and the shipments of planting materials have contributed to a drastic change in pathogen population, resulting in the establishment of pathogen species to regions where they have no natural predators.  This might cause a serious economic impact as well as environmental effects and if developed they become difficult to get rid off. In the absence of their corresponding predators and parasites to keep them under control, these species population rise unrestrictedly. Invasion of the pathogen through international trade of plants parts and woody plants as well as live plants affects our economy, environment, and society.

The observable economic effects are usually quantifying costs such as estimating losses in agriculture crop products or measurable cost of herbicide or biological spraying program. Also, predicting the of ecosystem losses and interacting associating between invasive and native species (Mooney et al., 2005). However, quantifying the economic cost becomes complicated when an invasive species affect both agricultural and natural environments. Most emphases on economic cost have concentrated on the cost of invasion in the US (Pimentel et al.,2005).

Severally unintentional movements of pathogen and insect species into new areas have emerged as a major agricultural pest. For instance, one of the most detrimental disease affecting citrus production was found around 1998 and has become the greatest threating disease contributing to main economic lost in  revenue more than $7.8 billion, redundancy loss of about 7,513 and yielding loss of more than 160, 000 acres since 2007  (Southeast Farm Press, 2016).  The estimated cost of non-indigenous pest and diseases and their management has been around   $120 billion per annum in the USA (Pimentel et al.,2005), adding to this damage caused by invasive species globally is predicted at more than $1.4 trillion annually  (Pimentel et al., 2001). However, the damage associated with non-native plants pests differs from effects from the production level by causing a decrease in product quantity and quality as well as a general impact on society by enhancing food insecurity. An example of socio-economic effects from plant pest was observed in the nineteenth century, Phytophthora infestans, responsible for potato late blight caused the Irish potato starvation. In recent times, yearly economic lost from late blight is predicted to be around €1 billion in Europe (Haverkort et al., 2008) and $5 billion per annum globally  (Haldar et al.,2006).

A report from the government of Canada has projected invasive species have contributed to the economic cost of $34.5 billion yearly  (Canada 2004). Impacts on Canada’s agricultural sector was described by Swanton et al. (1993), that the estimated mean yearly loss as high as $984 million, with losses of $372 million in eastern Canada and $612 million in western Canada   (Swanton et al.,1993).

Environmental effects become very devasting and in several instances not reversible. Foreign invaders compete with native species, changes the genetic population of related species, proliferates and spread diseases (Shine, 2007).  In countries such as New Zealand, the main contributing factor of native biological diversity loss has been associated with biological invasion of alien species (Clout, 2001). Similarly, in South Africa, invasive plants are known to be the maximum risk to biological diversity  (Heywood and Brunel 2009).  Exported plants via global market have been described to pose a risk to species. Estimation of about 400  out of 958 species have been identified as a threat under the US Endangered Species Act are at risk by invasive species (Pimentel et al., 2005). Hence, biodiversity loss might alter the elasticity of the community to future instabilities and lead to a reduction in ecosystem functions and amenities that are beneficial to human well-being (Mace et al., 2012).  Invasive pathogens might interrupt the activities of the whole local ecosystems and impact on other connected elements such as hydrology, recreation and public facility (Waage et al., 2005). In regions that are often highly invaded by introduced plants have reported a drastic decrease in biodiversity (Pimentel et al., 2001).An example is the sudden oak death outbreak in California that adversely affected wildlife food chains as well as land values (Ivors et al., 2006). Similarly, the discovery of  Phytophthora cinnamomia root pathogen, infected more than 3000 plant species and has since then evolved world-wide for over 150 years from it main source inside south-east Asia (Hardham, 2005). It is now seen as the main threat in south-west Australia and remains a devasting pathogen in forest region and other ecosystems globally (Hardham, 2005).

3.1 Risk analysis

Assessing the risk imposed by international trade in plants and wood products is essential for biosecurity measures. Risk analysis comprises of three main components: (1) pest risk assessment, (2) detection, evaluation, and selection of risk mitigation options (3) risk communication (Cock 2003; FAO 2007).  The pest risk assessments process is utilized to detect possible problem species, entry pathways and to ensure execution of anticipatory protection measures. The number of potential biological invasive species introduced is numerous but only small portion are often described in detail (Brasier 2008). Since the threat from anonymous species is real but unmeasurable, some scientific researchers have suggested a risks analysis method that takes into account pathway of entry and generic classification of pest and diseases instead of specific organisms (Cock 2003; Brasier et al., 2008).

Even though not all the risk analysis factors can be achieved thoroughly. For instance, it is not possible to inspect all imported cargo; importing countries usually depend on their trade counterpart to take the required procedures to reduce the risk of contamination. This reliance might bring less execution and monitoring of treatment processes on the parts of exporting countries (Clarke, 2004). With this inadequate inspection process among participatory countries may increase the threat of new species introducing to importing destinations.

3.1.1 Measures to minimize the risk of introduction

Phytosanitary measures have been put in place to minimize pest and pathogen movement and dispersal into new areas.  This includes treatments that are applied to wood parts and plants parts to decrease the potential of moving pest from exporting to importing states (FAO 2010).  The IPPC have an international standard, that outlines certain requirements to enhance elimination of pest and pathogens or making them unproductive. These methods are often seen as the major ways of pest risk decrease, however, integrated approach or combining other measures can increase the effectiveness of eradicating pest risk (FAO 2002b).  Few of these treatments have been highlighted below.

Heat treatment has traditionally been utilized to minimize the moisture content of wood and to eradicate pests harboring in wood such as nematodes, insects, and fungi.  The use of lethal heat treatment procedures begun in the 1980s, to check the movement of pinewood nematode from its origin to other places. This measure was to restrict the distribution of the nematode and its insect vector. It was reported that temperature ranging from 52.1oC and higher killed all pinewood nematodes in wood (Smith 1991).  Hence, the incorporation of the time-temperature schedule into European import rules for wood products that originated from pinewood nematode-infested areas.  This protocol was later accepted as a treatment for wood packing such as crating, pallets and many others  (FAO 2002a).

Chemical treatments: Liquid chemical are applied as sprayed or dip into wood tissues with vacuum, heat process or pressure. An example is sawn wood sprayed or dipped in chemical close to the surface kills fungi and insects close to the wood surface and provide protection against further infestation by these organisms (   (Schauwecker 2006, Uzunovic et al.,2011).  It has been suggested that the highest chemical penetration into wood tissue is obtained when chemicals are applied with vacuum, pressure usually called thermal processes or chemical pressure impregnation  (Marshall et al.,2008).  Consideration of factors such as the duration, proper packaging, and storage condition of the treated wood before delivery is essential to avoid re-infestation  (Leal et al.,2010). Also, potting, soil and containers for transporting plants parts for planting must be well treated with the appropriates chemical to avoid pest and pathogen movements.

Fumigation of wood commodities in closed containers with gaseous chemical. The wood products are exposed to fumigant prepared according to manufactures protocol for a significant amount of time long enough to kill and contained in wood tissues to prevents subsequent infestation (FAO 2010). This process has indicated increased protection against broad-spectrum of the wood pest. However, there some limitation associated with this approach such as wood moisture content due to penetration of chemical into wood tissues (Ren et al., 2011).

Integrated approach: combining the various phytosanitary measures with rules and regulations by the inspections agencies at the various borders can provide an effective and long-term decrease of biosecurity risk via international trading in plants parts and wood products for planting. A single method in some instances may not provide full protection against pest risk, while the combination of treatments such as heat, fumigation, and chemical can provide broad and efficient pest management. This concept has been referred to as systems approach (FAO 2002b), previously known as integrated control or integrated pest management (Smith and Reynolds,1966).

4.0 Discussions and Conclusions

International trade in wood and plant parts for planting represents the main common pathway through which non-native forest insects and pathogens have arrived in the US and other European countries. In addition, international shipment of plants is increasing worldwide, as proved by the review presented here on plant imports to, and exports from, various countries have also attributed greatly to the development of new pest and pathogen impacting greatly on the plant life and health. Previously, plants parts and woody plants parts such as stems and scions were before transported to the US mostly for plant breeding purposes and as propagation stock, but currently, there is a sharp growth trend in large quantities of plants being cultivated abroad for domestic planting or for retail sales. In this regard, non-native forest insect and pathogen invasions may probably increase in the future under the current system; thus, it is important to address this anticipated and developing invasion pathway.

It is obvious that some plants become invasive and affects our economy and environment, thus becoming biosecurity concerns. While some will disagree that these reports on effect are often overstated in the literature and in some cases not based upon data generated by employing an empirical approach. With continued increases in international trade, importing countries can expect to see more introductions of new invasive plants. Biosecurity agencies have responsibilities to avoid the introduction of invasive plants as pests in international trade. Preventing the entry or introduction of new species is considered the most efficient, cost-effective approach to limiting the threat of biological invasion. Once a species is established in a new location, its control, containment, and eradication can be very costly and time-consuming. A key factor identifying and addressing main pathways for introduction of invasive alien species. Preventing introduction and spread of alien species, through risk analysis, improved interception methods, and mitigation treatments have therefore been a focus of national and international efforts.

As wood undergoes processing, its phytosanitary risks are generally reduced. For instance, greater phytosanitary risks are associated with international movement of round wood with bark. As bark is removed, and sawn wood is produced, the risks decrease significantly through this production process. Untreated and forest products can present high phytosanitary risks. Therefore, reinforcing the various treatments methods (integrated approach) can offer the potential to address this unknown diversity of pests to plant health. However, these conventional approaches to pest and pathogen elimination have challenges. Hence, developing new approaches to risk suppression, thus new treatment and systems of phytosanitary measures are necessary.

Risk analysis provides a systematic method of strategically setting priorities for research, mitigation, and eradication efforts. However, it should explicitly acknowledge gaps in information, identify uncertainties, and consider global, local, and regional factors terms of economic impacts due to forest damage, market restrictions, and higher management and control costs. Improving existing technologies may ultimately lead to enhancement of avoidance and declining the risks due to invasive species. The more that is known about the effectiveness of particular preventive and mitigation measures, the better countries will be able to respond to the requirements of existing trade agreements. A commodity-based assessment of these measures provides additional refinement of current knowledge.

International agreements between institutional bodies such as the World Trade Organization’s Application of Sanitary and Phytosanitary Measures and the International Plant Protection Convention have to revise their rules and regulations enforced on trade restriction to meet Morden biosecurity standards necessary to protect plant health. However, this restrictions must be backed with scientific proof as reported via threat assessment (FAO 2005b). An example is the International Plant Protection Convention (IPPC) organization that seeks to ensure the global framework for plant security via incorporation of International Standards for Phytosanitary Measures (ISPMs) for conserving plant resources. Interestingly, the organizations and research body involved are assessing the problems, conducting trials and developing better approaches to addressing pest risk. Finally, there should be a mass education program that should highlight the importance of protecting natural resources. This can reduce the various impact on ecosystems and biodiversity as well as minimizing the economic cost of pest eradication.


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