Forest pest management strategies
The movement of insects and diseases has been facilitated by increased long-range air travel and reduced travel time, international trade of agricultural and forest products, and the international exchange of plant material. Invasive species can be extremely destructive and have had damaging effects in both the developed and the developing world. This issue together with invasiveness of tree species, breeding for insect and disease resistance, genetically modified organisms (GMOs) and introduction of new genotypes is being addressed under the umbrella of Biosecurity in Forestry.
Forest protection is an integral part of sustainable forest management. Good management including the use of appropriate species and provenances to meet prevailing environmental conditions and end use requirements, and planting materials of optimal physiological and genetic quality, coupled with good silviculture, is the key to a healthy forest. The best line of defence in forest protection is prevention of pest introduction and spread through international and national phytosanitary legislation. The International Plant Protection Convention (IPPC), deposited with FAO, is an international multilateral treaty for cooperation in plant protection. The purpose of the IPPC is to secure common and effective action to prevent the spread and introduction of pests of plants and plant products and to promote appropriate measures for their control. As of June 2013, 179 countries were contracting parties to the convention. More than 30 International Standards for Phytosanitary Measures (ISPMs) have been endorsed through this system and are now legally binding standards.
ISPMs provide guidance that is broadly applicable for forest health, monitoring, the safe transfer of germplasm, and trade in forest products. FAO has prepared a written guide, Guide to implementation of phytosanitary standards in forestry, to clarify how these ISPMs apply to forestry.
Integrated Pest Management (IPM)
Despite international and national phytosanitary measures and information exchange, pests still continue to move between and within countries and given suitable climatic conditions and the absence of indigenous natural enemies, are quick to establish. Monitoring and survelliance is thus important to ensure that new incursions are discovered before extensive damage occurs, and to provide data to support decisions on appropriate tactics of control once a problem has been detected.
Integrated pest management (IPM): “is the careful consideration of all available pest control techniques and subsequent integration of appropriate measures that discourage the development of pest populations. It combines biological, chemical, physical and crop specific (cultural) management strategies and practices to grow healthy crops and minimize the use of pesticides, reducing or minimizing risks posed by pesticides to human health and the environment for sustainable pest management.” (Source: FAO, NSP Division).
The International Code of Conduct on the Distribution and Use of Pesticides is the worldwide guidance document on pesticide management for all public and private entities engaged in, or associated with, the distribution and use of pesticides. The Forest Stewardship Council (FSC) is the forest management certification system that promotes the responsible management of the world's forests and prohibits the use of highly hazardous pesticides.
The use of IPM implies that pest management programmes are designed as an integral part of forest management, including both prevention and control strategies. Emphasis is placed on understanding the underlying causes of outbreaks, on pest monitoring, on the use of selection and tree breeding for resistance and on the maintenance or gradual improvement of the overall health of forests, rather than on controlling pests once they have become a problem.
Forest pest management options
Two sets of complementary strategies for dealing with invasive species are: prevention and early detection; and response, which includes eradication, containment, control and mitigation. Many agencies have been advocating the concept of biosecurity which is a strategic and integrated approach that encompasses the policy and regulatory frameworks (including instruments and activities) that analyse and manage risks in the sectors of food safety, animal life and health, and plant life and health, including associated environmental risk. It covers the introduction of pests and diseases, the introduction and release of genetically modified organisms and their products, and the introduction and management of invasive species and genotypes.
Prevention and early detection
Prevention is the first line of defence against biological invasions and is also the most cost effective since once an invasive species becomes established, it is extremely difficult and hence costly to eradicate it. An important first step in prevention is the identification of species capable of becoming invasive, possible susceptible sites and more importantly, the pathways in which they can be introduced. The more comprehensive approach of identifying pathways rather than individual species results in a greater concentration of effort where pests are more likely to enter a country which not only avoids wasting resources elsewhere but also helps in the identification of more species, vectors, and pathways. Once pathways are identified then potential prevention tools and methods can be more specifically developed.
Some of the important tools used to prevent the entry and establishment of invasive species include:
-- public information and education;
-- risk assessments and environmental impact assessments for intentional introductions;
-- national and international regulations on prevention and quarantine measures and their enforcement with inspections and fees;
-- treatment of imported commodities, including through fumigation, immersion, spraying, temperature treatment, ultraviolet sterilization, and pressure;
-- trade restrictions.
Early detection of alien species should be based on a system of regular surveys - general, site-specific or species-specific, to identify newly established species. Although not all alien species become invasive, the costs of those that do become invasive suggest that a precautionary approach to the issue is best. If alien species are identified early, the chances for eradication will be high in particular because for some invasive species there can be a long lag period between initial introduction and subsequent population explosion. The longer species go undetected the fewer the options for its control or eradication and the more expensive any intervention will become.
Early detection is highly dependent on the capacity of individuals to recognize both native and alien species. As a result, a large component of this step is training, not only of national professionals responsible for surveying but also for any persons that spends time in the natural environment such as farmers, gardeners, forest workers, ecologists, tourism workers, photographers, hikers, etc. Trained professional national workers should be able to not only recognize native and alien species and the ecological effects of alien species but also they should be able to use databases, keys, manuals and other identification sources. Early warning systems which include lists and datasets of recorded or potentially invasives, in given countries, time sets and conditions are important tools in this regard.
Finally a contingency plan outlining the actions that should be taken once an alien species has been identified or an invasion is suspected, should be developed.
Response includes eradication, containment, control and mitigation.
When the preventative and early detection measures have failed to stop the introduction of invasive species, eradication is the preferred next method of action. Eradication involves the elimination of the entire population of an alien species, including resting stages, in managed areas. As a rapid response to early detection of an alien species, eradication is often the key to a successful and cost-effective solution. Careful analysis of the costs involved and the likelihood of success must be made before any eradication attempts are made. Some groups of organisms are more suitable for eradication such as plants, terrestrial vertebrates, some terrestrial invertebrates and in some cases insects. Also, well established populations and large areas of infestation are unsuitable for such programmes.
Successful eradication programmes must:
-- be scientifically based;
-- ensure that all individuals of the target population are susceptible to the technique being used thus ensuring that eradication of all individuals is achievable;
-- build support from the public and all relevant stakeholders;
-- ensure that the legal and institutional framework is sufficient for dealing with the issue;
-- secure sufficient funding;
-- ensure through prevention measures that there is no immigration of the target species into the area;
-- put in place a method to detect the last survivors;
-- include a subsequent monitoring phase to ensure that eradication has been achieved, and to prevent re-invasion;
-- ensure that techniques are environmentally, socially and ethically acceptable;
-- include any necessary measures to restore ecosystems after eradication.
Eradication programmes involve several control methods as outlined in the control section below.
Containment is a special form of control aimed at restricting the spread of an invasive species and to contain the population in a defined geographical range. The methods used are the same as those described for prevention, eradication and control. An important component of containment programmes is the ability to rapidly detect new infestations of the alien species spreading from the defined containment area or into new areas, so that control measures can be implemented quickly. In cases where eradication is not possible, containment of the invasive species into a defined area can be very effective in saving other regions of a country.
The long-term reduction in density and abundance of an invasive species to below a pre-set acceptable threshold is the aim of control programmes. Suppression of invasive populations below such thresholds can favour native species. Control methods including mechanical control, chemical control, biological control, habitat management, and hunting or a combination of these, have all been used successfully in controlling invasive species.
Not all options for the control of invasive species are practical, effective, economically justifiable, or environmentally sound for application in forests. In the forest sector, control measures should be integrated to maximize yield and profit while minimizing negative environmental impacts. Some other options that are suitable include cultural techniques, such as seedling management, planting patterns, buffer zones, ecoclimatic matching, pest and pathogen resistance; mechanical methods, such as cutting, bulldozing and shading; biological control; and integrated pest management.
If eradication, containment and control methods have failed in managing an invasive species, the only option is to accept the species while mitigating the impacts to other species and the environment. The focus here is on protecting the native species rather than harming the alien species.
Mitigation methods can include translocation of a population of species to an ecosystem that has not been invaded and alterations in the behaviour of desired species such as conditioning species to use breeding areas inaccessible to the invaders or artificial feeding sites.