• Damping-off

  General Pythium is considered a ‘weak pathogen’, meaning that it can usually only affect plants that are in a sub-optimal condition or suffer from stress, caused for example by too much water, too high or low temperatures or sudden fluctuations in temperature. Pythium aphanidermatum mostly occurs at higher temperatures in the soil or irrigation water. Pythium aphanidermatum mostly occurs in young plants and damage is more extensive in young crops.

• Bacterial canker of tomato

  General Clavibacter is a quarantine organism in Europe, which means that strong efforts are used to prevent the bacterium from entering. When the occasional infection is found, strict measures are taken to eradicate the infection. In tomato, growers must either destroy the infected crop entirely or, if the crop is old, only the plants in the infected area, with a substantial buffer zone. Replanting can only take place after thorough disinfection

• Dwarf bunt

  General Tilletia controversa is a plant pathogen. It is a fungus known to cause the smut disease TCK smut in soft white and hard red winter wheats, as well as dwarf bunt. Damage symptoms Tilletia controversa causes (bunted) heads that are slender and remain green longer than healthy heads. The glumes are opened either on some or on all spikelets, showing the bunt (smut spore) they contain, which is larger than a normal kernel. The bunt balls are

• Loose smut of barley

  General Ustilago nuda f.sp. hordei affects barley and can destroy a large proportion of the crop. It is also known as barley smut, or loose smut of barley. Damage symptoms Infection by Ustilago nuda f. sp. hordei r emains invisible until head emergence. The first sign of infection is the appearance of a smutted ear. Instead of normal tissue, the ear contains a mass of olive-brown smut spores. Life cycle and appearance of Loose smut of barley The

• Verticillium wilt

  General Verticillium species are non-specific plant pathogens. Many species are saprophytes, V erticillium albo-atrum and Verticillium dahlia e are the most important plant pathogens. Verticillium dahlia causes verticillium wilt and early dying of potato. Damage symptoms Verticillium species mostly cause wilting of plants. The wilting starts at the lower leaves. These leaves are pale-green, then orange-yellow. In the beginning the plant seems to

• Pierce's disease of grapevine

  General Xylella fastidiosa is a gram-negative bacterium which is limited to xylem tissue. It has many hosts, many of which show minor or no symptoms. More and more plant species are discovered as hosts. Xylella fastidiosa is best known in grapevine, stone fruit (peach and plum) and citrus, where it causes diseases such as Pierce's disease of grapevines, phony peach disease, plum leaf scald, citrus variegated chlorosis and quick decline syndrome.

• Wheat bunt

  General Tilletia tritici and Tilletia laevis only differ in one gene and easily hybridize. There is debate whether they should indeed be considered separate species, since they cause the exact same symptoms. Tilletia tritici and Tilletia laevis cause diseases such as common wheat bunt, stinking smut, karnal bunt of wheat. Damage symptoms Plantsinfected by Tilletia tritici and Tilletia laevis are hard to distinguish from infected plants before head

• Bacterial spot

  General Xanthomonas vesicatoria is a bacterium that causes bacterial leaf spot on peppers and tomatoes. Damage symptoms Xanthomonas vesicatoria in tomato causes small, water-soaked spots on leaves which are first round and become more angular as they grow. The centre of the lesions may fall out as they become drier. Under humid conditions, the spots may merge with lesions on the petioles and stems and form long dark streaks. On fruits, first small

• Bacterial soft rot, bacterial stem rot

  General Erwinia carotovora subsp. carotovora has recently been renamed Pectobacterium carotovora . It is one of the pectolytic bacteria causing extensive bacterial rots (bacterial soft rot, bacterial stem rot). Damage symptoms In tomato, Erwinia carotovora subsp. carotovora or Pectobacterium carovora causes bacterial stem rot as well as soft rot. Stem rot is first noticed when plants wilt at the time of first harvest or after that. The pith disintegrates

• Angular leaf spot

  General Xanthomonas fragariae is a leaf spot disease found in strawberry. Damage symptoms Xanthomonas fragariae initially causes small, water-soaked lesions on the underside of the leaf. They enlarge to angular spots, often limited by the small veins. The distinctive feature is the way the lesions look when using different light sources: when reflected light is used, the lesions look dark green, but when transmitted light is used, they are