Sources of knowledge on tree health range from the forester and extension officer to the researcher. Surveys are the traditional way of determining the incidence and severity of a problem, but they require time, vehicles and money. Surveys also depend on the availability of researchers and local staff, which tend to be increasingly few. Local knowledge is a frequently neglected source of information which can provide fresh insights and a wider perspective on tree health problems without the need for expensive and lengthy surveys.
Many local people rely on trees for products and services and carefully observe changes to the health of trees. These observations often lack scientific detail but are valuable for their potential to describe a problem and to suggest fruitful lines of investigation. The ability of local people to diagnose symptoms accurately may be limited, and separate problems may be considered as the same one (see Plates 3.5 and 3.6). However, careful interviews can be extremely helpful in explaining the history of a disease or disorder, when it first occurred or where it is most damaging. This information can save time and money and contribute new information that would otherwise be difficult or even impossible to collect.
The scientific literature is a more traditional source of information (see Annex 2). The Internet offers unlimited access to information, but it is recommended that directed searches be performed via the useful sites suggested in Table 5.
Table 5. Important Internet sites
The forestry compendium has some information on insect pests and
diseases (less so on disorders or abiotic factors); the crop protection
compendium includes some tree species
CABI online databases, compendia and published abstracts are frequently
available through universities, libraries and research institutes
Provides definitions, gives links to other information sources and outlines FAO's activities in forest health
Provides good information notes on specific forest pests
Photos of insect pests and diseases on trees, mostly in North America and Europe
Generic forest health surveys guidebook
Provides information on locations, contacts, programmes and activities of the World Agroforestry Centre (ICRAF)
Provid es information on contacts, programmes and activities of the International Union of Forestry Research Organizations (IUFRO); Division 7 covers forest health
Gateway to information on plant diseases
Software that helps with diagnosis of crop problems
Glossary of forestry terms in several languages