Phytophthora kernoviae is a plant pathogen that mainly infects European beech (Fagus sylvatica) and Rhododendron ponticum.

For the European beech (Fagus sylvatica) host symptoms include dark brown to blue black lesions on the trunk ranging in size and shape depending on severity of the infection.

[6] Both shrubs and trees share the characteristic symptoms of leaf necrosis with lesions on the stem and trunk proving the severity of this disease.

[7] Phytophthora kernoviae spreads most quickly and detrimentally in moist conditions such as direct rainfall and also those of heavy humidity.

[9] This range suggests that it may have originated in a temperate climate, possibly China, Taiwan, the Himalayas, or even New Zealand before being introduced to the UK.

While there are no known insect vectors for the disease, humans can transport spores via agricultural equipment, on shoe bottoms, and direct plant movement.

[15] Sporangia are only formed on hosts with susceptible foliage, trunk cankers have not exhibited sporulation and do not spread disease.

After infection if the conditions are correct, Phytophthora kernoviae produce sporangia that are dislodged by natural occurrences and spread to nearby plant tissue.

[14] Since 2003, Phytophthora kernoviae has caused marked damage to ornamentals and species of trees in the Southwest United Kingdom.

The oomycete pathogen was first discovered in the 1990s, yet only gained widespread attention when it was identified as one of the causal agents, along with P. ramorum, of sudden oak death.

[17] Furthermore, the aggressive nature of Phytophthora kernoviae makes it an even more significant concern considering that the mainland of the UK has diverse ecosystems that are susceptible to the impact of this plant pathogen.

[17] As of 2005, it was confined to a relatively small area of Cornwall but has also been found in Wales and Cheshire suggesting that the pathogen may be being spread by the horticultural trade.

Due to the national and international demand of these plant products, Phytophthora kernoviae has initiated recent concern after being found Vaccinium myrtillus, commonly called Bilberry.

[20] Before infecting the inner bark of European Beech trees, the pathogen causes leaf necrosis and the dieback of shoots in the under-foliage of the forest along with ornamental species.

[20] This pathogen's adaption for aerial dispersal is a key factor in its transmission from initial ornamental host to tree species.

Furthermore, the pathogen present in the xylem leads to local dysfunction that furthers to damage the plant tissues, and move into previously healthy bark.