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It is not for nothing that the harlequin willow bears its name. The willow species, also known as Salix Integra, convinces with variegated leaves, eye-catching flowers and a shape that is remotely reminiscent of the wild shaggy harlequin costume. But what to do if the splendor of this gem is suddenly clouded by brown discolored leaves? We explain which causes can be responsible for this and which measures against diseases, parasites and co. help.
Typical diseases of the harlequin willow
If you believe relevant advisors, the biggest enemies of the harlequin willow are too much sun and too little water. Nevertheless, it is also troubled by various diseases, the effects of which can range from minor visual impairments to endangering the entire tree. Although the list of possible tree diseases is sometimes very long, the number of pathogens that specifically affect willows and thus also the harlequin willow can be limited to a very small number.
rust
The clinical picture commonly referred to as rust is a fungus that spreads rapidly, especially in the hot and humid summer months. Its striking red coloring has led to its catchy name.
- Symptoms: Red dots, later areas on the underside of the leaves, yellow dots on the upper side of the leaves
- Cause: Cronartium ribicola fungus
- Effects: disturbance of leaf metabolism, discoloration to brown and fall of the leaves up to the complete bareness of the tree
- Remedy: use fungicides, remove and destroy infested areas (e.g. burn)
Rust on a pine, Cronartium ribicola
Marssonina disease
Also in the case of Marssonina disease (also shoot tip drought), the pathogen is a fungus. Although this is particularly noticeable on the tips of young shoots, it unspecifically affects all parts of Salix Integra, with the leaves being the weakest link affected first.
- Symptoms: Brown necroses up to 3 millimeters in size, later the spots merge to form completely brown leaves
- Cause: Marssonina salicicola fungus
- Effects: the foliage dries out and falls off, and in the case of intensive infestation over several years massive damage up to and including death of the entire pasture
- Remedy: Use of suitable fungicides, pruning of affected shoots, preventive removal of autumn leaves as a winter spore store
Marssonina leaf spot on rose leaf
willow scab
Although willow scab also affects young shoots and leads to long-term damage here in particular, an infestation with this fungus first and foremost manifests itself in brown leaves. These cling to the tree for an unusually long time, so that intensely infested trees temporarily leave an autumnal impression as early as summer.
- Symptoms: brown discoloration of the entire leaves, caused by punctiform discolouration, also attack on the shoot tips of one-year-old shoots
- Cause: Pollaccia saliciperda fungus
- Effects: Inadequate supply of the tree due to the lack of photosynthesis performance, reduced growth performance due to damage to the young shoots
- Remedy: Removal of infested shoots, removal of dead leaves as spores to prevent further spread, use of fungicides in the case of severe infestation
galena
The name is given by the silvery-grey shine of the leaves, which mainly affects young plants. Depending on the location, however, this sheen can easily be confused with hoarfrost etc. and overlooked, so that only the more serious effects catch the eye. The infection occurs particularly frequently after pruning, since the pathogens easily migrate into the harlequin willow through cuts.
- Symptoms: initially the leaves have a silver-grey sheen, later the young shoots die off and the foliage turns brown and dries out
- Cause: Fungus Chondrostereum Purpureum
- Effects: low growth performance due to the omission of the foliage that carries out photosynthesis
- Remedy: Application of fungicides through nesting in the tree substance is hardly possible, generous pruning of infested areas
watermark disease
The disease is indicated by the markings on the affected shoots. The reason for this is the blockage of water-carrying pathways, which can result in an undersupply of entire branches. This disease is one of the very few willow-specific diseases that can be traced back to a bacterial pathogen.
- Symptoms: Brown discoloration and dying of leaves, and later growing larger shoots
- Cause: bacterium Brenneria Salicis
- Effects: From the affected area, there is no longer an adequate supply of water and nutrients, which means that healthy areas are also intensively affected after a local infestation
- Remedy: Remove affected branches, otherwise no known remedy
danger: The disease is considered contagious and thus easily transmitted to neighboring trees. Thus, if an infestation is detected, action should be taken quickly. In the case of an intensive infestation, the only way to prevent it from spreading is to fell the entire pasture.
pests
In addition to the actual diseases, there are also various parasites whose effects on leaves, twigs and the entire tree are usually very reminiscent of real diseases. It is therefore worth knowing and being able to identify the most common parasites:
willow leaf beetle
This species of insect lives and reproduces on the leaves of willows, including the harlequin willow. By feeding on leaf substance, these are specifically attacked and damaged.
- Appearance: Depending on the species, approx. 4 to 9 millimeters long, oblong-round body with a light base color and dark spots, other species have a round body with a dark, mostly greenish color
- Damage: Feeding damage, initially infestation of the leaves, which turn brown due to increasing damage, resulting in insufficient supply and death of twigs, branches and ultimately the entire tree
- Control: Use of suitable pesticides, usually self-regulating in the case of low infestation by predators (especially birds)
spotted willow leaf beetle, Chrysomela vigintipunctata
willow borer
The willow borer belongs to the wood borer family. It affects pastures in general, including the harlequin pasture, sometimes with serious consequences. It is not the moth itself that is critical, but its larvae, which in the course of their development form feeding tunnels in the wood and penetrate the tree.
- Appearance: moth about 65 to 80 millimeters long, stocky to clumsy physique, gray color with fine line markings, caterpillars up to 100 millimeters long with yellow body and broad red back coloring, head and neck shield black, very shiny body
- Damage: Destruction of the tree's pathways, resulting in undersupply and browning of the leaves, with intensive infestation individual branches or the entire pasture dying off
- Control: only possible as long as eggs are present and caterpillars are on the wood surface, then use e.g
Wood eating from the willow borer