Harlequin willow gets brown leaves: what to do?

Not for nothing does it wear Harlequin Willow your name. The type of willow, also known as Salix Integra, convinces with variegated leaves, striking flowers and a shape that is vaguely reminiscent of the wild shaggy of a harlequin costume. But what should be done if the splendor of this piece of jewelery is suddenly clouded by brown discolored leaves? We explain which causes can be responsible and which measures can help against diseases, parasites and the like.

Typical diseases of the harlequin pasture

If you believe the relevant advice, the greatest enemies of the harlequin pasture are too much sun and too little water. Nevertheless, she 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 can be very long, the number of specifically willows and so also the harlequin willow, infesting pathogens to a very small number enclose.

rust

The disease, commonly referred to as rust, is a fungus that spreads rapidly, especially in hot and humid summer months. Its distinctive red color has led to its catchy name.

• Symptoms: red spots, later areas on the underside of the leaves, yellow spots on the upper side of the leaves
• Cause: Cronartium ribicola fungus
• Effects: Disruption of the leaf metabolism, discoloration to brown and fall of the leaves up to the complete bare tree
• Remedy: Use fungicides, remove and destroy infested areas (e. B. Burn)

Marssonina disease

The pathogen is also a fungus in Marssonina disease (including shoot tip drought). Although this occurs particularly prominently at the tips of young shoots, it affects unspecifically all parts of Salix Integra, the leaves being affected first as the weakest link will.

• Symptoms: Brown nectroses up to 3 millimeters in size, later the spots merge into completely brown leaves
• Cause: mushroom Marssonina salicicola
• Effects: The leaves dry out and fall off, and in the case of intensive infestation over several years, massive damage up to the death of the entire pasture
• Remedy: Use suitable fungicides, cut back infected shoots, preventive removal of autumn leaves as a winter spore store

Willow scab

Although willow scab also affects young shoots and leads to long-term damage, an infestation with this fungus manifests itself first and foremost in brown leaves. These stick to the tree for an atypically long time, so that intensely infested trees sometimes leave an autumnal impression even in summer.

• Symptoms: brown discoloration of the whole leaves from point discoloration, also infestation of shoot tips of annual shoots
• Cause: Pollaccia saliciperda fungus
• Effects: insufficient supply of the tree due to the lack of photosynthesis, reduced growth due to damage to the young shoots
• Remedy: Removal of infested shoots, removal of dead leaves as a spore store to prevent further spread, use of fungicides in the event of severe infestation

Galena

It is named after the silvery-greyish sheen of the leaves, which mainly affects young plants. Depending on the location, this shine can also be slightly covered with hoarfrost, etc. confused and overlooked, so that only the more serious effects catch the eye. The infection occurs particularly often after pruning, as the pathogens easily migrate into the harlequin pasture through cuts.

• Symptoms: the leaves initially have a silver-gray sheen, later the young shoots die off and the leaves turn brown and the leaves dry out
• Cause: Chondrostereum purpureum fungus
• Effects: low growth rate due to the elimination of the leaves that carry out photosynthesis
• Remedy: The use of fungicides by implanting them 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 ducts, which can result in an undersupply of entire branches. This disease is one of the very few willow-specific disease patterns that can be traced back to a bacterial pathogen.

• Symptoms: brown discoloration and death of initially leaves, later also shoots of increasing size
• Cause: Brenneria Salicis bacterium
• Effects: From the infected area onwards, there is no longer a sufficient supply of water and nutrients, so healthy areas are also intensely affected after a local attack
• Remedy: Remove affected branches, otherwise no remedy known

Attention: The disease is considered contagious and can therefore easily be transferred to neighboring trees. Thus, if an infestation is detected, action should be taken quickly. In the case of intense infestation, the only option to prevent spreading is to cut down the entire pasture.

Pests

In addition to the actual diseases, there are also various parasites, the effects of which on leaves, branches and the whole tree are mostly reminiscent of real diseases. It is therefore worth knowing the most common parasites and being able to identify them in this way:

Willow leaf beetle

This species of insect lives and reproduces on the leaves of the willow trees, including the harlequin willow. By nourishing the leaf substance, these are specifically attacked and damaged.

• Appearance: depending on the species approx. 4 to 9 millimeters long, elongated, round body with a light basic color and dark spots, other types of round body with a dark, mostly greenish color
• Damage: damage caused by eating, initially attack on the leaves, which turn brown as the damage increases, as a result of insufficient supply and death of twigs, branches and ultimately the entire tree
• Control: Use of suitable pesticides, with low infestation mostly self-regulating by predators (especially birds)

Willow Borer

The willow drill belongs to the wood drill family. It attacks willows in general and also harlequin willow with sometimes considerable consequences. It is not the butterfly itself that is critical, but rather its larva, which in the course of its development forms feeding ducts in the wood and invades the tree.

• Appearance: butterfly approx. 65 to 80 millimeters long, stocky to plump physique, gray color with fine line drawings, caterpillars up to 100 millimeters long with a yellow body and a broad red color on the back, the head and neck shield black, very shiny body
• Damage: Destruction of ducts in the tree, as a result of undersupply and browning of the leaves, in the case of intensive infestation, individual branches or the entire pasture die off
• Control: only possible as long as there are eggs and caterpillars are on the wood surface. B. Use of quassia soap broth or chemical pesticides will no longer be effective after the caterpillars have penetrated the tree