What Is Willow Scab Disease – Learn How To Treat Willow Scab Disease

What Is Willow Scab Disease – Learn How To Treat Willow Scab Disease

By: Teo Spengler

Willow scab disease attacks different types of willow species in Europe and the United States. It can attack weeping willows but is not one of the more common weeping willow diseases. Willow scab is caused by the fungus Venturia salciperda. Scab on willow trees usually doesn’t cause serious harm unless the black canker fungus (Glomerella miyabeanais) is also present. Read on to learn about how to recognize and how to treat willow scab.

Scab on Willow Trees

Willow scab is a fungal disease that causes leaf symptoms, followed by brown spore masses at the base of leaves. The symptoms of scab on willow start with dark spots on the leaves. These can be brown or black, and cause the leaves to wilt, shrivel up and die.

In time, as the willow scab disease progresses, the fungus spreads to the stem tissue at the bases of leave petioles. There, it forms olive-brown velvety spore masses. This happens most often in wet spring weather. Look on the underside of the leaves and along the rib and veins for these fruiting bodies.

Although scab on willow trees can attack any almost any Salix tree, it is not considered one of the common weeping willow diseases. In fact, weeping willows (Salix babylonica) are the most resistant willow species to this disease.

How to Treat Willow Scab

Willow scab disease causes only minor damage to your trees if they are healthy. However, repeated infections may slow a willow’s growth and reduce its vigor.

If you are wondering about whether effective willow scab treatment exists, you’ll be happy to hear that it does. You can control willow scab on your backyard willows with a combination of good cultural practices and chemical applications.

How to treat willow scab with cultural practices? First, you’ll need to trim out all of the infected parts of the willow tree, including stems and twigs. Don’t forget to sterilize your pruners with a bleach and water mixture to avoid spreading the fungus.

In addition, keep your trees vigorous with sufficient irrigation and regular fertilizer. The disease does much less damage to healthy trees than vulnerable ones.

Finally, properly timed fungicide applications can be part of your willow scab treatment. This is especially important if your tree is also infected by the black canker fungus.

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Corkscrew Willow Problems

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Corkscrew willows (Salix matsudana “Torulosa”) have twisted and contorted branches that make them an attention-getting tree year-round. It grows quickly to about 30 feet tall, and grows best in U.S. Department of Agriculture zones 4 through 8. The cut branches are decorative and frequently used in floral arrangements, and the twisted appearance makes it an interesting subject as a bonsai tree. Even large branches are easy to root by placing the cut end in water. Corkscrew willows do have several challenges associated with them.


Willow (Salix spp.)-Twig Blight (Scab)

Cause Venturia chlorospora has been reported in Oregon and V. saliciperda in Washington. These fungi survive on old willow leaves on the ground and also on infected twigs. Spores spread during spring rains. Salix petandra , S. triandora , and S. viminalis are reported as fairly resistant S. alba 'Calva' is immune.

Symptoms Shortly after new foliage develops in spring, brownish spots appear along leaf midribs leaves scorch, wither, and drop. Defoliation is considerable, particularly toward limb terminals. Small brownish black cankers on twigs, which girdle limbs and twigs may also occur.

  • In home landscapes, rake all fallen leaves and twigs and burn them before the spring growth period.
  • Prune out diseased limbs and twigs if practical.
  • Plant resistant types.

Chemical control In spring, spray two or three (3) times beginning when new leaves first appear and repeating at 14-day intervals, especially before wet weather.

  • Armada 50 WDG at 3 to 9 oz/100 gal water. Do not use a silicone-based surfactant. Not for nursery or greenhouse use. Group 3 + 11 fungicide. 12-hr reentry.
  • Eagle 20 EW at 6 to 12 fl oz/100 gal water. Pest not on label but is effective on other Venturia diseases. Group 3 fungicide. 24-hr reentry.
  • Myclobutanil 20 EW T&O at 6 to 12 fl oz/100 gal water plus spreading agent. May observe a PGR effect. Group 3 fungicide. 24-hr reentry.
  • Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker. Group M3 fungicides. 24-hr reentry.
  • Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens at 1 fl oz/gal water. Group 3 fungicide. H
  • Tebuject 16 is registered for tree injections. The number of capsules used is based on tree size. Group 3 fungicide.

Reference Sivanesan, A. 1976. Venturia saliciperda. CMI Descriptions of Pathogenic Fungi and Bacteria, No. 482. Surrey, England: Commonwealth Mycological Institute.


The signs and symptoms of root rot in willow trees are varied and can be mistaken for other infections. Willow scab shows as oddly-shaped brown spots on leaves these become more prevalent during damp and wet conditions. As the fungus spreads, the brown spots turn green this is a sign of spores beginning to spread. Crown gall can be identified by the tumors forming on the roots, stems or branches of the willow tree the tumors will eventually overrun an infected area if left untreated. Leaves will begin to turn color from green to yellow, then tan to brown this starts at the upper canopy with the leaves farthest from the roots. Root bark will take on brown coloration fungal spores will form as bronze colored stringy hair from the bark. Root bark will tear and slide off as the roots rot the inner bark becomes slick and gummy. White threaded mats under the bark begin to form.

  • There are two types of pathogens that can cause root rot in weeping willow trees one is a fungus, the other is a bacterium.
  • Root bark will take on brown coloration fungal spores will form as bronze colored stringy hair from the bark.

Planting and Growing the Dappled Willow Tree

If you want to plant a dappled willow tree in your garden, plant them in early spring or mid-to-late fall or early spring. Both seasons guarantee air temperature and warm soil — important factors in dappled willow tree planting.

Location

In terms of location, go for an area that has plenty of sun. Areas with partial shade will work but places with full sun can yield more vibrant colors. The more sun the tree gets, the more vibrant the color of the leaves and stems. Dappled willow trees need full sunlight, or at least

Soil texture

Whether you choose a partial shade or full sun, always prioritize the soil texture. Dappled willow trees thrive in slightly acidic soil conditions, with the pH ranging between 5 and 7. While these colorful shrubs grow well in moist soil, it doesn’t grow well in standing water. Dappled willows only thrive in moist, well-draining soil.

Planting

When planting the tree, dig a hole that’s an inch shallower than the tree’s root ball height and twice the size of its root ball. Plant the tree in the hole before filling it with soil. Next, add a three-inch layer of mulch around the tree.

Pests and diseases

In terms of pests and disease, the most common ones that affect dappled willow trees are spider mites, caterpillars and mildew. Since this tree is a forgiving plant, most gardeners just prune infected stems and destroy them.

Anthracnose diseases, which are often caused by fungi, often develop during the dappled willow’s growing season. This disease causes the leaves to drop, as well as trigger recurrent attacks that are detrimental to the tree. So if you see signs of an infection, dispose and remove the affected parts.

Finally, it’s not necessary to encourage growth, but dappled willows respond well to pruning. Regular pruning encourages more vibrant leaf colors since it encourages plant growth. If you want to prune your shrubs, you can cut up to a third of the branches and it won’t impact the root system. Schedule your pruning in late winter.


Willow Scab

Caused by the fungus Fusicladium saliciperdum, willow scab is one of the more serious diseases that affect willow trees. Damp, wet weather creates favorable conditions for the spread of this infection. Oddly-shaped brown spots appear on the leaf surface along the main veins and midribs. Spots turn olive green as spores begin to form. Younger leaves are especially prone to willow scab and may have spots all along the midribs and veins. Badly infected leaves will dry up and drop. The fungus will spread into the twig or young branch and dark cankers may develop which results in the die-back of branches and twigs. Treat willow scab with a copper fungicide always follow manufactures instructions when using chemicals. Enlist preventative measures by pruning trees of dead twigs and branches, rake up all fallen leaves and diseased matter and burn.

  • Willow trees are a favorite among tree lovers for their dramatic, elegant appearance.
  • The fungus will spread into the twig or young branch and dark cankers may develop which results in the die-back of branches and twigs.

What diseases do willow trees get?

Disease Pathogen/Cause
Crown gall Agrobacterium tumefaciens
Black canker Phyalospora miyabeana
Blight or scab Venturia saliciperda

Disease. Common willow diseases include root rot, which can infect the tree's root system and cause overall health decline, and willow scab, a fungus which kills new growth and causes cankers on the tree. Fungal infections can usually be battled by pruning and destroying diseased branches.

Also Know, how do you know when a willow tree is dying? Look for signs of decay and uprooting at the base of the tree, where the trunk rises from the ground. Soft, rotting wood and an abundance of bored insect holes around the base signals a dead weeping willow tree.

Besides, how do you bring a willow tree back to life?

Prompt care must be given to a willow if you notice any leaf discoloration, stunted growth or defoliation.

  1. Pour 70 percent denatured alcohol and 30 percent water into a spray bottle.
  2. Dig next to any suckers growing from the root ball of your willow tree.

What is killing my weeping willow?

Weeping willows are susceptible to many fungal diseases and a few bacterial diseases, but only cotton root rot ordinarily causes them to die within hours or days. Cytospora canker (Cytospora chrysosperma), crown gall (Agrobacterium tumefaciens) and a deficiency of iron can also kill weeping willow.


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