Diseases and pests of serviceberry

Fire blight

Although Amelanchier is not among the first species affected by fire blight, as a member of the Rosaceae family, it can unfortunately harbour this bacterium. Very serious, it can cause the death of the bush within three months. It is crucial to spot the early signs. The bacterium Erwinia amylovora responsible for this is subject to obligatory control in nurseries, as well as in private gardens. In these, it spreads from ornamental plants such as Cotoneaster, Pyracantha, and Hawthorn, which are the most sensitive species.

Identification

The first symptoms are visible on the flowers in spring: they wilt and dry out. Next, the tips of the shoots begin to bend and dry out as well. Young shoots may suddenly turn reddish or black. A whitish ooze can be observed on the affected parts.

If you observe these types of symptoms, it is essential to investigate without delay. Laboratory analysis can confirm the disease, but before that, by cutting a branch, you can check for other signs. → Read Eva’s article on fire blight to properly identify this disease.

The disease spreads to the shoots, branches, and even the trunk, causing cankers that lead to the sudden death of branches or the entire tree by blocking the sap. They then harbour the disease during winter, which spreads to other plants in the Rosaceae family via the whitish exudates present on the affected parts.

Treatment

The reason this disease is so serious is that there is no effective treatment. It is believed that copper-based treatments can help limit new infections, but they should be used sparingly due to their toxicity to ecosystems.

The crucial point in the fight is early detection.

Prevention and Legislation

It is therefore important to detect the symptoms of fire blight early and to remove the contaminated shoots. Fire blight often appears during warm (between 12 and 24°C) and humid periods. The bacterium enters through natural openings such as the nectaries of flowers or the stomata (pores located beneath the lamina), as well as through injuries caused by hail, wind, or pruning.

Symptoms of Fire Blight

Entomosporiosis

Cryptogamic disease typical of plants in the Rosaceae family, Entomosporiosis is caused by the fungus Entomosporium maculatum. It causes only aesthetic damage in ornamental gardens; however, in orchards, the attack can be significant.

Identification

On an amelanchier, small round spots, 1 to 3 mm in size, appear reddish and then covered with characteristic brown crusts. In cases of severe attack, the leaves turn yellow and fall.

On older leaves, the spots darken with a grey central area surrounded by a brown margin. Small black punctuations, the spores, are observed at the centre of the spots. In cool, humid conditions, the disease can spread to the petioles and young shoots, leading to the weakening of the tree in severe cases, where spots are also seen on the fruits, which may even mummify.

Prevention

This fungus primarily develops in humid weather during spring and summer when temperatures are below 20 °C. A dry spell, on the other hand, slows the disease. During winter, the fungus survives on fallen leaves, branches, and the trunks of infected trees. It produces spores in humid conditions, carried by wind and rain, which can contaminate other trees in spring or later, particularly during fruit formation.

For prevention, it is important to avoid overly dense plantings, promote air circulation between plants, and within the crown of the bush by pruning. Also, systematically disinfect your pruning tools with 90% alcohol.

Treatment

Prepare a solution of 20 g of Bordeaux mixture per litre of water as soon as the first symptoms appear and spray:

1. In autumn, at leaf fall.
2. In early spring: one spray at bud burst and a second one month later.
3. In particularly humid springs or as soon as the first symptoms of spots appear, repeat the operation several times until fruit formation.

Collect and burn infested leaves and fallen fruits.

→ For more information, read the article on Entomosporiosis.

Symptoms of Entomosporiosis

[powdery mildew]

If you notice a white fluff on your Amelanchier leaves, it is likely a symptom of powdery mildew, common in gardens. It is caused by microscopic fungi and is favoured in confined environments with warm, dry air.

It is characterised by a fluffiness in the form of spots or patches, with a farinose appearance and a greyish-white colour, present on the leaves and flower buds. In cases of severe infestation, these organs may become deformed.

On ornamental plants, the damage is aesthetic, but on fruit-bearing plants, the quality of the fruit can sometimes be affected. Powdery mildew appears in spring or late in the season on fruit crops.

Prevention

Once again, it is important to space your plantings, encourage air circulation, and prune if necessary. The decoction or horsetail manure is recognised as a good preventive measure against powdery mildew. It is also important to mulch to maintain good moisture in the soil. If you notice some damage, it is crucial to cut away the affected parts, collect the dead leaves, and burn them all.

Treatment

Several natural treatments are possible and have shown their effectiveness provided they are applied consistently. Based on baking soda, garlic, or skimmed cow’s milk, they should be sprayed regularly.

→ To discover the natural recipes in detail, read the article on powdery mildew.

Fluff of powdery mildew on a rose stem