Dutch elm disease
Fungal disease that attacks especially elms. The causative fungus is Ophiostoma spp. The disease is transmitted between roots of adjacent specimens, but mainly by spore transmission by vector insects. Inside the tree, the spores colonize the vascular system, releasing toxins that block the xylem and ultimately kill the tree. The main symptom is a general wilting of the plant, progressive from the secondary branches to the main ones. As the root is weakened, the tree is susceptible to being felled by the wind.
Mainly in those of the Cupressaceae family. In humid seasons and with moderate or warm temperatures, spores are released that are disseminated by the wind, insect vectors, pruning tools, and splashing drops of water from rain or irrigation. They infect healthy trees from wounds or natural openings. The conidia accumulate on the trunk and branches, causing cankers, from which the inoculum spreads to the entire plant and to other healthy trees, thus continuing its biological cycle.
Polyphagous fungus that generally behaves as a saprophyte, without causing significant damage. When the tree is weakened, the mycelium continues its growth from the base of the tree towards the main roots, then the secondary ones and finally the finer ones, causing girdling of the roots and the neck and finally death by vascular collapse. It can also infect by contact with roots of other adjacent trees, so that it can affect large areas of land. It manifests itself like other vascular diseases, with generalized yellowing in the crown.
It is a disease generated by various types of fungi, especially from the genes. Colletotrichum and Gloeosporium. It affects many ornamental trees, almost always on the leaves, although in adult specimens it can cause bumps on the trunk. The spots generated cover the veins of the leaves, which are deformed, and in the case of young leaves, they die and fall, constantly weakening the tree.
The fungus that causes this disease reproduces, which is dispersed by the wind and reaches the leaves, on which it spreads, in the form of white powder that will prevent the nutrition of the areas of the leaf that it covers. It attacks species as common as the plane tree, the catalpa, oaks…. The main sign is the appearance of a layer with a floury or cottony appearance and a white or grayish color, formed by the mycelium and the conidia. It will also cause the deformity of the growing leaves. In a strong attack the leaves turn yellow and later dry up.
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.