The fungus Fusarium circinatum (F. circinatum) is the causal agent of pitch canker disease. It almost exclusively affects pine (Pinus) species, but Douglas fir (Pseudotsuga menziesii) can also be a host.
This disease is a serious threat to pine forests wherever it occurs, because of the extensive tree mortality, reduced growth and degradation of timber quality which it causes. Multiple branch infection can cause severe crown dieback, and eventually lead to the death of the tree. This aggressive fungus can also cryptically infect pine seeds, and then cause damping-off of young seedlings (death as a result of the fungal infection being encouraged by damp conditions).
It is considered that pitch canker of pine could become established in the European Union, based on the following evidence:
- F. circinatum has already been reported at some locations in the EU, in Spain, Italy, France and Portugal;
- host trees are present in the EU - pine species are widely present, while Douglas fir has scattered distribution only; and
- climatic conditions are suitable in parts of the European Union.
Suitable hosts and climatic conditions are present in the UK. It is therefore considered that it would pose a threat to pine forests if it entered the UK.
Infected seedlings show typical damping-off symptoms, but these are not unique to pitch canker infection: needles turn red, brown or chlorotic (pale or yellow as a result of producing insufficient chlorophyll), and die from the base upwards, or the entire seedling dies.
Root infections are most often observed on seedlings in nurseries, but can also occur on exposed roots of larger trees in landscape plantings. Above-ground symptoms do not usually become apparent until the pathogen reaches the crown and girdles the stem, causing yellowing of the foliage. Resin-soaked tissue might be observed after removal of the bark on the lower part of the stem.
Symptoms of aerial infection include yellowing of the needles, which turn red in time and finally drop, and dieback of the shoots. Multiple branch tip dieback, due to repeated infections, can lead to significant crown dieback. The female cones on infected branches can also become affected and abort before reaching full size. Thereafter, cankers can appear on the shoots, on the main stems, and even on the trunk, associated with resin bleeding.
Pitch canker of pine mostly infects pine species. In North America, its main native hosts are Slash pine (P. elliottii), Longleaf pine (P. palustris), Patula pine (P. patula), Radiata pine (P. radiata), Loblolly pine (P. taeda) and Virginia pine (P. virginiana). It has also been recorded on more than 30 other pine species, including the European and Mediterranean species Aleppo pine (P. halepensis), Maritime pine (P. pinaster) and Scots pine (P. sylvestris); various North American species planted in Europe, such as Lodgepole pine (P. contorta) and Eastern white pine (P. strobus); and various Asian species e.g. Japanese red pine (P. densiflora) and Japanese black pine (P. thunbergii).
There are occasional records on Douglas fir, but only associated with limited damage, although it can act as a pathway for spreading the disease.
Pitch canker of pine occurs in 12 south-eastern states of the USA, and in the Monterey Peninsula and coastal areas of California. It is also present in Mexico, Haiti, Chile and South Africa (but only in nurseries).
It is present in Japan, Korea and possibly Iraq.
Pitch canker of pine is a relatively recent arrival, and has been reported in nurseries and forests in several countries, namely France and Italy (from where it is now considered to have been eradicated), and Spain and Portugal (https://gd.eppo.int/taxon/GIBBCI/distribution). The occurrence of the pathogen is most common in coastal areas of affected EU countries. The pathogen is not present in the UK.
Pitch canker of pine was added in 2002 to the EPPO A2 action list of pests, and EPPO member countries at risk are therefore recommended to regulate it as a quarantine pest. It has since become subject to European Commission Decision 2007/433/EC, which invoked provisional emergency measures to prevent introduction into and spread within the EU. It includes legislation on plant imports and movement within the EU of soil, growing media and wood materials. APHA must be notified of any imports of pine from the EU as per the requirements of the Plant Health Order 2005.
Seeds of pine species imported from countries where F. circinatum is present should also be free from the pathogen, and can be subject to specific tests. There is a risk of introduction with soil but, in general, most EPPO countries prohibit the import of soil, and restrict the import from other continents of plants with soil. These measures should be effective against pitch canker of pine.
The action that would be taken to deal with a discovery of pitch canker of pine in this country is set out in our contingency plan.
Although F. circinatum is not known to be present in the UK, there is a risk of its being accidentally introduced. We therefore urge the public, and especially importers of wood and plant materials, and tree and plant professionals, to remain vigilant for signs of it, and to report suspicious symptoms to us. Please report suspected cases to us with our Tree Alert on-line pest and disease reporting form.