Thematic study on forest pests

Figures are rarely available on losses attributed directly to infestations of forests, trees and forest products by insects and diseases, particularly in developing countries and countries in transition. Thus, in addition to seeking quantitative information for FRA 2005, FAO compiles qualitative profiles of individual pest problems by country. Information is collated from many sources, through expert contacts in the countries, via the Internet and in literature searches. The study is ongoing and constantly updated. Data are indexed, making it possible to highlight information on pest distribution that could indicate potential invasiveness between neighbouring countries. Information on the host preference of individual causative agents can be extracted, as well as breakdowns of pests at the country level.

The impact of pests on the forest sector is often underestimated, as illustrated in the following examples:

  • Since an infestation of Dendroctonus ponderosae (mountain pine beetle) was first detected in interior British Columbia in 1994, an estimated 240 million m³ of timber on 11.3 million hectares have been lost, at an estimated cost of US$1.7 million per year. The beetle is spreading fast across Canada and threatens to move south into United States forests. Huge investments in control are now necessary, with more than US$82 million recently committed by the Canadian Government.
  • In eastern and southern Africa, three accidentally introduced aphids were the first specific conifer pests to invade the region, and they became the most damaging pests of these species. Since their initial introduction, the pine wooly aphid, Pineus boerneri, the pine needle aphid, Eulachnus rileyi, and the cypress aphid, Cinara cupressivora, have proliferated throughout southern and eastern Africa and continue to spread. It was conservatively estimated that, by 1990, C. cupressivora had killed trees worth approximately US$44 million and was causing a loss in annual growth increment of a further US$14.6 million per year. In addition, the two pine aphids were causing a further loss of approximately US$2.4 million per year to annual growth increment in pine forest plantations in the region. This economic data was instrumental in securing resources to mount a biological control programme, which led to substantial reductions of incidence of at least the cypress aphid.
  • In New Zealand it is estimated that the forest industry spends US$0.60/ha on the monitoring of diseases and pests, in comparison with US$3.50/ha on fire defence. Yet average annual losses to disease amount to some US$137 million, whereas losses to fire are just US$682 000.

At this time, 25 profiles have been completed from five regions. As more countries are included, there will be more opportunities for comparison. This information should not only increase awareness of the importance of forest health, but also encourage countries to collect data that will enhance the accuracy of future global forest resources assessments.

Forest health Web site:

last updated:  Sunday, June 10, 2007