Forest pest management, Natural Resources Canada

Forest pest management

Native insects and diseases play an essential ecological role in Canada’s forests.

By consuming trees and other plant material, forest insects and micro-organisms contribute to healthy change and regeneration in forest ecosystems. They help renew forests by removing old or otherwise susceptible trees, recycling nutrients and providing new habitat and food for wildlife.

However, it’s not for their ecological benefits that forest insects and diseases sometimes make national news. When infestations are so severe they destroy or damage large areas of commercially valuable forest, or infest Canadian forest products bound for export, then insects and diseases—whether native or alien—become “pests.”

Mountain pine beetle, spruce budworm, gypsy moth and Dutch elm disease are all examples of well-known forest pests that have led to significant losses in value of Canadian forests.

What’s what: native, alien, invasive

Forest insects and diseases in Canada are typically classified into three broad categories:

  • Native: Indigenous species that have existed in Canada for thousands of years. Outbreaks occur periodically. Examples are spruce budworms and mountain pine beetle.
  • Alien: Species introduced into Canada’s forests within recent history. They are also referred to as “exotic,” “non-native” and “foreign.” Examples include emerald ash borer, brown spruce longhorn beetle and Dutch elm disease.
  • Invasive: Insects and diseases that spread beyond their known usual range.

Both terms, “alien” and “invasive,” refer to shifts from one ecosystem to another, not to shifts across national borders. So, even organisms that move into new ecosystems within the same country can be considered alien and invasive if they extend beyond their usual geographic range. The spread of mountain pine beetle from British Columbia’s lodgepole pine forests to Alberta’s jack pine forests is an example of a native forest insect behaving invasively.

This video describes the role fire and mountain pine beetle play in the forest and how forest management strategies like prescribed burning can help return forest ecosystems to a state of balance and health. Duration: 5:03

From friend to foe

Native forest insects and diseases are generally of little concern when they exist at non-damaging population levels.

It is when populations of these native species increase beyond an acceptable threshold, or when alien or native species behave invasively that concerns arise. If ecological or economic damage results in measurable impacts—such as a decline in ecosystem health or large reduction in the available wood fibre—then the insect or disease outbreak is seen as being a disturbance and active management intervention may be considered.

The challenge for forest resource managers is therefore two-fold. First is to assess the risks posed by potential and actual outbreaks and spread. Second is to apply risk-based decision-making to manage forest ecosystems in a way that minimizes the negative impacts of outbreaks and maximizes the positive impacts.

Forest pest management in Canada

The focus of forest pest management in Canada is on:

  • maintaining the health of the country’s forests by managing native pest disturbances that threaten ecosystem values and the forest sector’s access to commercially important timber and related resources
  • preventing the entry and spread of alien species into the country.

To achieve these ends, Canada—the provincial, territorial and federal governments—takes an integrated pest management approach. In integrated pest management, interventions carried out are based on knowledge about what their short- and long-term impacts might be, and involve targeting both the area and pest in question.

The responsibility for forest pest management in Canada depends on the nature of the pest and the location of outbreaks. This accommodates the variety of forest management practices and priorities that exist in this large and diverse forested nation. In general, forest ownership determines this responsibility: so, federal, provincial, territorial and municipal governments are responsible for pest management within their specific jurisdictions. Private forest owners are responsible for their own forest pest management.

The federal government is also responsible for management of regulated alien species wherever they occur in Canada.

All forest managers rely on scientific information and advancing technology to manage pests within their jurisdictions. The Canadian Forest Service (CFS) is the principal provider of scientific and technological support on forest pest matters to all jurisdictions, including federal agencies such as the Canadian Food Inspection Agency (CFIA) and Environment Canada.

The science and technology contributions of the CFS include: basic information on the identity, biology and ecology of forest pests and on ecological and economic impacts; and the development of expert tools and strategies in support of the evidence-based decision-making. The CFS plays a lead role in the National Forest Pest Strategy, an initiative by the Canadian Council of Forest Ministers to harmonize and share knowledge and expertise in the complex world of forest pest management.

Outbreaks of native insects and diseases are natural, recurring processes with many ecological benefits. However, they pose major problems when their severity or spread threatens forest productivity and competes with commercial forest values.

How to practice Integrated Pest Management?

Good agricultural practices in plant protection

One of the biggest problems with many of the developments in IPM over the years has been the tendency to generalise and make recommendations for farmers across large and highly heterogeneous areas. This has been true for all manner of input recommendations including fertilizers, pesticides and crop varieties. This problem, ecological heterogeneity, has also severely limited the effectiveness of government monitoring and forecasting systems. All of these practical issues vary on a small spatial scale. This local specificity requires that farmers become IPM experts. The recommendations or decision criteria of each approach reveal a steady progression in the accommodation of ecological heterogeneity and farmer control of agro-ecosystem management.

Maintenance of crop health is essential for successful farming for both yield and quality of produce. This requires long-term strategies for the minimization of pest and disease occurrence preferably by enhancing natural control mechanisms, growing a “healthy crop”. Specific measures include the use of disease- and pest-resistant crops, rotation of crops, including those with pasture, to provide disease breaks for susceptible crops, apply non-chemical control practices (thermic, mechanical) as applicable and as last resort the tactical use of agrochemicals to control weeds, pests, and diseases following the principles of IPM and guidelines of good application practices. Any measure for crop protection but particularly those involving substances that are harmful for humans or the environment has to be carried out with state of the art knowledge and equipment. Integrated Pest Management should focus on the following points:

  • Use resistant cultivars and varieties, crop sequences, associations, and cultural practices that minimize the pressure and maximize biological prevention of pests and diseases.
  • Maintain regular and quantitative assessment of the balance status between pest and disease and beneficial organisms of all crops.
  • Apply pest and disease forecasting techniques where available.
  • Understand and use non-chemical pest and disease management practices.
  • Decide on interventions following consideration of all possible methods and their short- and long-term effects on farm productivity and environmental implications in order to minimize the use of agrochemicals, in particular promote integrated pest management (IPM).
  • Store and use agrochemicals according to legal requirements, e.g. registration for individual crops, rates, timings, and pre-harvest intervals.
  • Assure that agrochemicals are only applied by specially trained knowledgeable persons.
  • Assure that equipment used for the handling and application of agrochemicals complies with established safety and maintenance standards.
  • Maintain accurate records of agrochemical use.
  • Avoid any point source pollution from agrochemicals resulting from use, storage, cleaning and disposal of products or application equipment.
  • Avoid impact on non-target areas of any pest and disease management activity.

IPM strategies are different for each crop, for a country, for a region, even for one location, depending on local varieties used, local agronomic practices and various crop protection options available. IPM can never be delivered in a “package”; it needs to be developed, adapted and tailor-made to fit local requirements. Designing and practicing effective IPM systems is about learning and continuously finding solutions to changing field situations and problems.

See also:  How to Get Rid of Camel Crickets (Naturally and Effectively)

Prevention and suppression of harmful organisms

Crop rotation; inter-cropping

If you plan to grow the same crops regularly, you will need to rotate them. Different crops needs particular nutrients in the soil and use these up at a particular level in the ground. At the same time, each kind of plant attracts its own particular pests and diseases, which soon become established around the crop. If you grow the same kind of crop in the same place season after season, the nutrients that the plant needs are quickly exhausted, the plants grow weak and stunted and quickly come under attack from waiting pests and diseases. Crop rotation is important if the rotation reduces inoculum. Crop rotations should be observed since there are many pathogens that survive on numerous types of both living and dead plant materials. Some crops, such as sorghum, pearl millet and maize, may drastically suppress weed population and reduce its biomass. Pearl millet may exhibit residual weed suppression in the following crop. It is obviously necessary to evaluate which rotations can be grown successfully in the agro-ecological zone to maximize yield and pest control.

Use of adequate cultivation techniques

Burning plant residues and ploughing the soil is traditionally considered necessary for phytosanitary reasons: to control pests, diseases and weeds. In a system with reduced mechanical tillage based on mulch cover and biological tillage, alternatives have to be developed to control pests and weeds and Integrated Pest Management becomes mandatory. One important element to achieve this is crop rotation to reduce the pest-risks associated with monocultures, interrupting the infection chain between subsequent crops (different sowing dates and distances between fields with the same crops) and making full use of the physical and chemical interactions between different plant species. Synthetic chemical pesticides, particularly herbicides are, in the first years, inevitable but have to be used with great care to reduce the negative impacts on soil life. To the extent that a new balance between the organisms of the farm-ecosystem, pests and beneficial organisms, crops and weeds, becomes established and the farmer learns to manage the cropping system, the use of synthetic pesticides and mineral fertilizer tends to decline to a level below that of the original «conventional» farming system (see section on Conservation Agriculture ).

Where appropriate, use of pest resistant/tolerant cultivars and standard/certified seed and planting material

Plant breeding has resulted in the development of a large number of varieties that are resistant to several kinds of diseases. Breeding is based on access to plant genetic resources, which can be conserved in the field and in gene-banks. Wild cultivars have low economic benefits in most cases, but often show resistance to locally occurring biotic and abiotic stresses; and cross-breeding of these varieties can result in the development of varieties that can perform better, by out-competing weeds, without the application of large doses of pesticides. A sustainable seed system will ensure that high quality seeds of a wide range of varieties and crops are produced and fully available in time and affordable to farmers and other stakeholders. Access to certified seeds will improve the uptake of farmers of higher-yielding varieties which can withstand stress and thus decrease environmental problems that are caused by use of pesticides (see section on Seeds and Plant Genetic Resources ).

Diseases: Control or Management?

Coping with plant diseases in the field is relatively difficult because the causal organisms (bacteria, MLO, fungi, virus and nematodes) are very small and cannot be seen moving around like insects or rats. The most important first step in thinking about diseases is to realize that diseases must be managed not controlled. What is the difference? Management means a complete set of activities that support each other. Management means that these activities are carefully planned and are implemented over several seasons, not controlled within a single season. Management included control methods for prevention, and control methods to slow down epidemics; diseases will never be completely eradicated — only populations reduced to very low levels. Management usually needs the cooperation of several farmers working together to reduce overall disease in an area. Management requires someone who can observe larger areas of disease incidence and levels of infection.

Weeds reduce yields by competing with the plants for sunlight, moisture, and soil nutrients. Weeds may affect farming in many ways. For example, fertilizer applied might not increase yields in weedy fields because weeds absorb nitrogen more effectively than many rice plants. Also weeds are harmful because they may be alternate hosts for insect and disease pests of the main crop, and provide shelter for rats. Usually weed problems are more serious in upland and rainfed areas than in irrigated lowlands. If weeds are left to grow in the field they can significantly reduce yields. Knowledge of the behaviour of weed species is often lacking in the basic information available for weed control in most developing countries. Control measures are generally adopted to reduce weed infestation at certain phases of the crop cycle and not to bring about a sustainable reduction of the infestation. In order to know when is the right time to implement control methods to reduce weed species productivity, knowledge is required concerning: weed productivity; time of germination/emergence; and the period of fruit-setting and/or emission of first vegetative organs. These studies also provide information on the negative or positive influence of certain biotic and abiotic factors on weed growth and development (see section on Integrated Weed Management ). Weed management must focus on the control of weed species, not only to avoid competition but also to prevent further build-up of weed seed bank in soil and eventually reduce it.

Field sanitation and hygiene measures

The pathogens that spread plant diseases and weeds can easily be spread by farmers and their machinery, as well as other people that visit farm fields. Although many pathogens are naturally present in the environment, they can also be spread by humans (faeces, clothing and machinery) and through inputs (mainly irrigation water). The main causes of contamination by pathogens that can be harmful to humans are the use of animal manure or sewage waste as organic fertilizer and the presence of animals in production areas. Composting of static piles and earthworms do not guarantee that micro-organisms have been inactivated. Wastewater and municipal wastes should only be used if effective disinfecting systems are available. Other ways of reducing the spread of potential plant diseases and weeds is to regularly clean farm machinery and clothing. Proper field sanitation and hygiene measures are an easy way to prevent diseases from spreading, but should always be combined with other measures, such as crop rotations and intercropping.

See also:  How to get rid of silverfish in your home

Protection and enhancement of important beneficial organisms

The configuration of the landscape can help to improve habitat for beneficial organisms for pest control and pollination (see section on Pollinator Management ). Many ways exist of increasing these organisms, such as conservation of keystone species/structures and natural habitats. In rice systems, natural pest protection can be increased by small rows of certain crops that attract the beneficial organisms in (or at the border) the fields. For other crops, larger fragments of natural habitat (e.g. Agroforestry ) are needed. Attention should also be given, where possible, to have a landscape that reduces the risk of the easy spreading of plant diseases. This means that borders between crops have to be established, based on the height and the distance that the pathogens/weeds can travel. Overall, a higher biodiversity will reduce the risk of pest outbreaks, whereas it will also benefit the biological processes that are needed for agricultural production and create diversification of income and risks (see section on Agricultural Biodiversity ).

Monitoring of harmful organisms

Monitoring of pests at a larger level (preferably transboundary) can help for the early warning, early detection. contingency planning, early reaction, promotion of environmentally sound control technologies and close collaboration and partnership with affected countries, national and international agricultural research centres and other international institutions. To strengthen the effort to address the challenges of large-scale emergencies arising from transboundary pests and diseases more effectively and to provide better coordinated and more timely assistance to affected countries, FAO created a Food Chain Crisis Management Framework (FCC). EMPRES Plant Pest and Disease will have a primary role in emergency prevention, early warning and risk assessment, and in stimulating synergy with the other EMPRES components. Whereas this is one larger component of monitoring, at farm level the farmers should also be aware of what different pests and beneficial organisms look like and what (if there is any) the tolerable level is in the field. Coordination can be done through farm organizations, but preferably also by communication with a national institute (e.g. through mobile phones), that can inform other farmers and provide measures that can be taken.

Establishment of Economic Threshold Levels (ETL)

The goal of training for IPM is to empower farmers to make their own decisions. These decisions are usually economic decisions about pest control and base their action on the question ‘if I don’t spray, will I loss some yield that worth more than the cost of the spray?’ The decision requires knowledge of the agro-ecosystem: recognition of pests and natural enemies, understanding of the interaction of pests and natural enemies. The decision also requires knowledge of the effect of pests on the yield of the plant and the effect of pesticides on natural enemies.

The Economic Threshold Level (ETL) is an attempt to improve decision making practices by using partial economic analysis on the impact of a control practice, such as spraying a pesticide. The ETL is computed usually based on three parameters using the following equation:

ETL = cost of control ($/ha)

[commodity value ($/kg) x damage coefficient (kg/ha/#pest/ha)

At the ETL, the benefits of spraying are equal to the losses caused by the insects in the field. There are many ways of making this definition, but they are usually based on the same parameters. What is the use of the ETL? Traditionally, when the ETL was surpassed (field populations are sampled and found to be higher than the ETL) the farmer was advised to spray. IPM now includes a larger analysis of the ecosystem. Other factors include levels of natural enemies, plant health and ability to compensate for damage, other investment opportunities, personal health, and weather are involved in the decision making process. The ETL is still useful a part of the analysis, but not the only analysis.

Monitoring of the success of the applied pest management measures.

Observing the fields regularly is necessary to assess crop development, diseases, weeds, rats, and insect pest populations. In most cases, an experienced IPM farmer does this observation during a short time (usually less than a few minutes per field) while carrying out other crop maintenance activities (irrigation, etc.). Observations should determine how the crop is growing and if there are pests or diseases causing yield-loss; remembering that not all injury causes yield-loss. Natural enemies are usually present and sufficient to keep pests at low numbers. Weather conditions, soil nitrogen levels, and degree of host plant resistance will determine if diseases will subside or become more serious. In the case of rats, community level dynamics determine rat infestations and control programs. IPM Farmers must be knowledgeable of these factors to properly and economically manage crops. In some cases natural enemies, plant resistance and plant compensation cannot prevent yield-losses due to weeds, rats, insects, or diseases. Proper assessments must be made to effectively and profitably manage the use of inputs such as labour, quality seed, resistant varieties, fertilizers, drainage systems, community organizing and pesticides in order to ensure profitable production. Observation skills and decision making are key to becoming an expert IPM farmer and require field level practice for most farmers and extension staff.

Sustainable non-chemical methods of pest control

After monitoring efforts in which pests are detected, farmers can compare the severity (damage to plants and number of pests per area) to the economic threshold levels that have been established. This can lead to the decision to take efforts to reduce pest occurrence, first by non-chemical methods of pest control, and if this is not providing satisfactory results, with chemical methods of pest control. Whereas this is useful at farm level, it would be better to also take into account the risk of rapid pest-spreading over a large area, by looking at the distance that pests can travel and the size of the area (mainly monocultures) that can be damaged by the pests. When the risk of spreading is high, early warning can result in more efficient and less environmentally damaging efforts to reduce the risk. Before pests become established, a smaller dose of pesticides will be needed than once the pests have reached the field. Exact measures will depend on the crop and landscape configuration, which means that monitoring is needed at ecosystem, or higher, level.

Pesticides as a last resort

There are several alternatives to chemical pesticides that have to be evaluated before deciding to use chemical pesticides. Alternatives include biological pest control agents (BPCA) that include microbial and botanical pesticides, as well as semiochemicals; all of which can be valuable components of IPM. The risk associated with these biological pest control agents are favourable in comparison with the conventional synthetic chemicals and in some cases they might even be acceptable in organic production systems. Application of these pesticides might be limited by their access and price, both of which can be promoted by more favourable policies. In order to facilitate alternative methods of pest control, a good understanding of each pest species and there natural predator should be available for farmers. This can be promoted by leaflets/flyers that include pictures of each species, together with possible treatment measures. Economical justification should also not only include the current cropping system, but also alternative cropping systems that might be more resistant to pesticides (e.g. crop rotations and intercropping) and that have been proven to be functioning in similar agro-ecological zones. A value should also be attached to health risks and labour requirement.

See also:  How To Get Rid of Bandicoot Rats in India, Rentokil Pest Control

Specific application of pesticides to reduce the impact on human health and the environment

Pesticides are necessary in some fields, in some years and in some areas. In many seasons, fields with a high diversity of crops do not need pesticides. Pesticides are very dangerous to both the person who uses the pesticides and to those that are living or playing near the fields where pesticides are used. Pesticides can kill aquatic animals, beneficial predators and parasites, and other beneficial animals such as pollinators. There is no use of pesticides that can be called «safe» to everything in the ecosystem. Even the very selective insecticide causes problems for the growth of shrimp and prawns. There is no «safe use of pesticides». It is only possible to avoid their use and reduce exposure when used.

Test on the dosage of insecticide which kills test animals are called Lethal Dosage tests. Basically the process is simple and depends on the fact that not all animals will die with the same dosage because some individuals are more sensitive than others. If a very low dose is applied to 100 individuals, only a few individuals will die. If a very high dose is given, then most of the 100 individuals will die. The dose at which 50 of the 100 (50%) die is called the 50% lethal dosage or LD50. The dosage at which 90% of the individuals die is called LD90. This is a moderately useful measure, except that even at low dosages there is still an LD10 in which 10% die. Lethal dosages are usually given in both oral (through the mouth) and dermal (exposure to skin) levels. But pesticides cause other effects besides death. Other symptoms of pesticide exposure include nausea, dizziness, headaches, fatigue, diarrhea, irritation of nose, eyes, and throat.

Scientific name

Hura crepitans L.


Hura brasiliensis L.

Common names

Sandbox tree, possumwood, monkey’s dinner bell, monkey’s pistol



Hura crepitans is native to the tropical regions of North and South America in the Amazon Rainforest.

Naturalised distribution (global)

Locations within which Hura crepitans is naturalised include northern Australia and eastern Africa.

Introduced, naturalised or invasive in East Africa

In East Africa, Hura crepitans is invasive in parts of Tanzania (Tropical Biology Association 2010). The editors found no records of its occurrence in Kenya or Uganda, though this does not necessarily mean that it is absent from these countries.


In its introduced range, Hura crepitans occurs in forest edges and gaps.


Hura crepitans is a tree growing to 40 meters high. It can be distinguished by its many dark, pointed (conical) spines. Its common name ‘Monkey-no-climb is in reference to the characteristic spiny trunk.

The leaves are papery thin, heart-shaped and up to 60 cm long.

The berry look-alike structure is actually the male flowers that have no petals. Male flowers grow on long spikes; female flowers are solitary. Male flowers are ovoid to conical (5 by 2 cm), mostly dark red in colour. Flower stalks (pedicels) up to 10 cm long; female flowers without pedicel; fruiting pedicel pendant to 6 cm; fruit oblate (3-5 x 8-9 cm) in diameter, reddish brown on colour, concave at the tip and base, longitudinally grooved.

Fruits are pumpkin-shaped capsules, 3-5 cm in length with a diameter of 5-8 cm; it has 16 carpels arranged radially around the central axis. Seeds are flattened and about 2 cm in diameter.

Reproduction and dispersal

The fruit of Hura crepitans opens with an explosive sound into segments, hence the name ‘dynamite tree’. Seeds are dispersed up to 14 metres away.

Economic and other uses

Hura crepitans is cultivated for medicinal and ornamental purposes. The latex is used as arrow poison and is said to cause ailing teeth to fall out. As medicine, it treats skin diseases, rheumatism, intestinal worms and has been used in the United States of America to prepare tear gas; bark extract is used to treat leprosy and wood used in light construction.

Environmental and other impacts

The large leaves of Hura crepitans enable the plants to grow in deep shade, allowing the plant to establish in undisturbed forest outcompete indigenous vegetation. H. crepitans is among the 14 commoner causes of plant contact dermatitis in the Dominican Republic. Tree fellers have to cover their eye since the sap causes temporary blindness. The segments of the woody fruits can cause dermatitis when they are used in bracelets and necklaces.


The precise management measures adopted for any plant invasion will depend upon factors such as the terrain, the cost and availability of labour, the severity of the infestation and the presence of other invasive species.

The best form of invasive species management is prevention. If prevention is no longer possible, it is best to treat the weed infestations when they are small to prevent them from establishing (early detection and rapid response). Controlling the weed before it seeds will reduce future problems. Control is generally best applied to the least infested areas before dense infestations are tackled. Consistent follow-up work is required for sustainable management.

The editors could not find any specific information on the management of this species.


Not listed as a noxious weed by the state or governments in Kenya, Tanzania and Uganda.


The pumpkin-shaped fruit of Hura crepitans was once used for holding fine dry sand used for blotting ink before the introduction of blotting paper, hence the common name ‘sandbox tree’.


Pacific Island Ecosystems at Risk (PIER). Hura crepitans : plant threats to Pacific ecosystems. Institute of Pacific Islands Forestry, Hawaii, Accessed March 2011.

Tropical Biology Association (2010). Usambara Invasive Plants — Amani Nature Reserve —


Agnes Lusweti, National Museums of Kenya; Emily Wabuyele, National Museums of Kenya, Paul Ssegawa, Makerere University; John Mauremootoo, BioNET-INTERNATIONAL Secretariat — UK.


This fact sheet is adapted from The Environmental Weeds of Australia by Sheldon Navie and Steve Adkins, Centre for Biological Information Technology, University of Queensland. We recognise the support from the National Museums of Kenya, Tropical Pesticides Research Institute (TPRI) — Tanzania and Makerere University, Uganda. This activity was undertaken as part of the BioNET-EAFRINET UVIMA Project (Taxonomy for Development in East Africa).

No comments

Добавить комментарий

Your e-mail will not be published. All fields are required.