Phytophthora is a pseudofungus (oomycetes, such as pythium), which affects numerous ornamental and agricultural species (palms, citrus, oak, cuprusaceae, conifers and eucalyptus). They tend to proliferate in moderate temperature conditions (15-30ºC), such as spring or autumn, especially in areas with high soil moisture, flooded or with very high groundwater levels. The main symptom is the drying of the most distal areas of the crown, which will not be able to receive enough water and nutrients because the root loses absorption capacity due to the action of the pathogen. Occasionally, exudations may also occur on the trunk, due to cracks in the bark due to the invasion of the pathogen from the vascular system.

With 3 main subspecies, (X. fastidiosa: subsp. fastidiosa, subsp. pauca and subsp. multiplex) this bacterium, aerobic, is transmitted by insect vectors that suck from the xylem and that will transmit the bacterium when "biting" in another tree . Once in the plant, it multiplies inside the vascular bundles, preferably at temperatures between 26-28ºC, to clog them and obstruct the flow of sap, which causes symptoms compatible with lack of water or lack of nutrients.

Caused by the bacterium Erwinia amylovora, it fundamentally affects numerous species, in particular the rosaceae (apple, pear…), both in ornamental and agricultural fields, where they produce significant economic losses. Laying dormant during autumn/winter, in spring, the bacterium becomes active, to spread through vectors such as insects, birds, wind or rain or pruning tools, after which it will infect all tissues of the plant, starting with the flowers and the leaves. young shoots, to subsequently produce massive necrosis of flowers, fruits, leaves and branches, with death of all the cells in its path, to finally colonize the trunk and cause the death of the plant. This causes a characteristic burnt appearance, which gives the disease its name. In addition, exudates can also be present in all organs.