Insect Pest Infestations

Primary reference(s)

FAO, 2019. Glossary of phytosanitary terms. International Standard for Phytosanitary Measures No. 5. Food and Agriculture Organization of the United Nations (FAO). Accessed 11 October 2020.

Additional scientific description

Insects are responsible for significant losses to the world’s total crop production annually. Not all insects are pests, but many are harmful to crops, forest trees, livestock and humans. One major reason for the occurrence of these pests is the expansion of monocultures in large areas at the expense of natural habitats, with crops and trees selected for their large size, high yield, nutritious value and economic value. This provides a highly conducive environment for herbivorous insects. In addition to agroecosystem-based integrated management practices during production, good post-harvest management and storage conditions are important in reducing losses caused by insect infestation in agriculture (FAO, no date).

A detailed glossary of phytosanitary terms was developed for the International Standards for Phytosanitary Measures. It was produced by the Secretariat of the International Plant Protection Convention for the Food and Agriculture Organization of the United Nations (FAO). Examples of relevant terms for insect pest infestation are given below (FAO, 2019): 

• Biological control agent: A natural enemy, antagonist or competitor, or other organism, used for pest control. 
• Incidence (of a pest): Proportion or number of units in which a pest is present in a sample, consignment, field or other defined population.
• Incursion: An isolated population of a pest recently detected in an area, not known to be established, but expected to survive for the immediate future. 
• Infestation (of a commodity): Presence in a commodity of a living pest of the plant or plant product concerned. Infestation includes infection. 
• Introduction (of a pest): The entry of a pest resulting in its establishment in the environment. 
• Official control: The active enforcement of mandatory phytosanitary regulations and the application of mandatory phytosanitary procedures with the objective of eradication or containment of quarantine pests or for the management of regulated non-quarantine pests. 
• Outbreak: A recently detected pest population, including an incursion, or a sudden significant increase of an established pest population in an area. 
• Pest: Any species, strain or biotype of plant, animal or pathogenic agent injurious to plants or plant products. Note: In the International Plant Protection Convention (IPPC), ‘plant pest’ is sometimes used for the term ‘pest’.

Metrics and numeric limits

Not available.

Examples of drivers, outcomes and risk management

The agriculture and forestry sectors face many risks, such as climate and market volatility, pests and diseases, extreme weather events, and an ever-increasing number of protracted crises and conflicts. Issues around outbreaks of animal and plant pests and diseases are of major concern due to their role in the biological disasters and in many food chain emergencies. The human food chain is under continuous threat with an alarming increase in the number of outbreaks of transboundary animal and plant pests and diseases. Crop pests, forest pests and animal diseases are among the costliest disasters in Africa – more so than in Latin America and Asia – accounting for over USD 6 billion in agricultural loss between 2005 and 2015, with insect pests ravaging up to 85 million hectares of forests, mainly in temperate North America (FAO, 2018).

There are over a million species of insect. These include some key species causing direct damage to crops and natural vegetation such as locusts, grasshoppers, armyworms and fruit flies as well as those that also function as vectors for the transmission of plant disease agents such as white flies, aphids, spittle bugs and mealybugs (FAO, 2021).

The most recent global-scale insect pest infestation is caused by fall armyworm (FAW) spreading to almost the whole of Africa and south and southeast Asia following its jump from Latin America to Africa in 2016. It is currently causing damage to millions of hectares, particularly on maize but also other crops, creating significant food security risks. The Food and Agriculture Organization of the United Nations (FAO) has launched a Global Action for FAW Control to facilitate international collaboration to combat the insect (FAO, 2020a).

Higher temperatures, severe and extreme weather events and drought stress can all result in reduced vigour of trees, making them more vulnerable to outbreaks of native and introduced pests and diseases. For example, the dieback of millions of hectares of pine forests caused by outbreaks of native bark beetles in Central America, Europe and North America is associated with climate change, impacts of extreme weather events and, in some cases, inadequate forest management practices (FAO, 2020b). 

Favourable climatic conditions, disruption of ecosystems and negligence of crop/forest hygiene contribute to growth in insect populations which can cause substantial damage regularly. In many cases, long distance spread of insects results from transportation of infested goods. Following principles of sustainable plant production, sustainable forest management and integrated pest management practices are the best approach for control, focusing on diversified production systems, regular surveillance, preparedness before potential outbreaks, and a rapid response to prevent escalation to unmanageable scales (Guzewich et al., 1997).

Post disaster needs assessment (PDNA) is designed to evaluate immediate needs for recovery and restoration for better disaster response. The focus of this mission, however, is on estimating socioeconomic impact; and currently does not take into account longer-term damage and loss caused to natural environments and forests. In addition, damage caused by small-scale fires, small windthrow events, and localised pest infestations remains largely unreported, despite meeting the universally established definition of a disaster (FAO, 2018).

Regarding insect pest infestations in forests, much of what is currently known about the damage and its assessment is in the form of research reports on the application of remote sensing and does not constitute a solid basis for a rigorous sectorspecific assessment (FAO, 2018).