Verticillium wilt

The Verticillium wilt is a fungal disease of plants. Verticillium dahliae and V. albo- atrum infect over 350 horticultural and agricultural host plants ( with more than 70 species of trees and shrubs ), in particular V. dahliae in many woody plants with the symptoms of " wilt " occurs. Both Verticillium species are soil-borne pathogens.

Often the wilt fungus is introduced in new plantings on a grand scale in the soils. Most important host plant, in practice, is the maple (including Norway maple, Japanese maple), follow him at some distance species of Catalpa, Cornus, Clematis, Castanea, Fraxinus, Robina and Aesculus and many other wood species. As less susceptible apply, inter alia, Alder, poplar, sycamore, birch, hornbeam and beech. Small pore trees like maple are more susceptible than large pores, because the vascular tissue for a long time remain functional and will not fall back every year with new ones. Monocot plants and conifers are not affected.

Diagnosis

On the basis of the following symptoms of the fungus is visible: shoots that have first expelled eg after winter in the spring new, suddenly show wilted leaves, although the plants are sufficiently watered and fertilized. The formerly green, firm leaves get a pale green color and become limp.

At thicker dead branches can be seen in the cortex that these " krisselig " is no longer smooth. Furthermore, it can be seen in the branch of a thicker section inside the timber a small crescent-shaped crescent. This suggests that the fungus is already grown deep in the woods and ever- waxing even after pruning.

Combat

Conventional spraying against fungus on the leaves of the plants do not work, since the fungus is protected inside the branches. You can reach most only temporarily a certain reduction of the harmful symptoms. Excised plant parts must not be chopped up on the compost heap or, as the fungus is highly infectious and can be spread over the compost.

Potentially infected garden shears, saws and other garden tools must be disinfected after use (eg flamed ).

The only way to research the fungus from a range that would be a deep soil exchange, which is often not possible, however, there would have to be then taken out all the plants and destroyed because of the adhering soil. Lowering the pH of the soil can lower the risk of infection.

Resistance

Deciduous trees that are resistant to the fungus, according to the Plant Protection Office Berlin are: Walnut ( Juglans ), willow ( Salix), oak (Quercus ) and Pear (Pyrus ).

When an infestation also insensitive to this fungus Conifers can be replanted, eg yew hedges or Thuja.

• Plant disease