Are orange spots on pear leaves a disease? How can I treat them?

Yellowish-orange spots on pear leaves are the main symptom of a fungal disease called rust, which can destroy up to 50% of the harvest in a single season. If left unchecked, the fungus attacks fruits and shoots, and in extreme cases, can lead to the death of entire pear trees.

Previously, no one knew about pear rust; the disease only recently began to appear. Where did this dangerous fungus come from, and how can it be eliminated?

Description of the disease, source of infection

The symptoms of various diseases are often very similar, but not in the case of rust, which is unmistakable. Until recently, the disease was observed only in southern regions, but now it is widespread, and outbreaks have become significantly more frequent. This is due to the desire of homeowners to decorate their plots with exotic ornamental plants.

The fungus attacks the entire shrub (needles, cones, shoots). External signs include various wounds, growths, and swellings. In the spring, bright yellow-orange, elongated, gelatinous organs form on the juniper, where spores develop.

Some scientists believe that juniper is not the primary source (carrier) of rust, but rather one of many. This is because wild juniper is quite common in other regions, and no signs of the disease have been observed on it. The main problem is its widespread introduction. Cultivation of atypical plant species is currently at the peak of popularity.

The process of fungal development

Commercial orchards don't pay attention to landscaping and don't grow exotic plants, so pears aren't susceptible to rust. However, in small private plots, this problem is acute. The most severe outbreaks occur in areas with frequent rainfall, and the high humidity in warm weather creates ideal conditions for fungal growth.

The fungus that causes the disease requires two plants to complete its optimal life cycle—in this case, a pear tree and a Cossack juniper. Having reached the desired stage of development on the conifer, the spores move to the pear tree, where a new stage develops, which then reinfects the shrub, and so on in a cycle. Neither the pear tree nor the juniper infect themselves. The infection cycle repeats every 1, 5, or 2 years; fruit trees become infected every two seasons.

The fungus overwinters under the bark of junipers. In the spring, small brown horns (spore-bearing organs) appear on the affected areas. When exposed to rain, the lesions turn orange and produce spores. In dry weather, the mature spores are carried by the wind up to 45–55 kilometers. Upon landing on a pear tree, the fungus begins a new stage of its development.

Signs of pear rust infection

The first signs of the disease appear on the leaves in late May. Upon inspection of the leaf blade, single, small, round, greenish-yellow spots are clearly visible. The spots gradually increase in size, and by July, they turn orange and acquire black specks.

In midsummer, dense yellowish-brown swellings form on the underside of the affected leaf, with spores forming within them. Severely affected leaves fall prematurely, thereby disrupting the tree's nutritional supply.

When rust reaches a critical stage, light green spots, then pinkish-red, appear on young and fruit-bearing branches. Stems gradually thicken and shorten (due to nutritional deficiencies). Severely infected branches dry out completely, while moderately infected branches continue to grow, but after a couple of seasons, the bark and wood begin to crack.

A pear tree infected with rust exhibits a weakened immune system, which is noticeable even externally: young stems fail to develop, fruits remain small, and leaves become dull. In this condition, the tree is unable to resist viruses, bacteria, fungi, and various pests. The pear tree reacts poorly to changing weather conditions, and its winter hardiness is significantly reduced.

How to treat rust on a pear tree

The most obvious solution to the problem, after the pear tree has healed, is to remove the juniper from the area. However, the wind carries spores over long distances, and there's no guarantee that the conifer isn't growing in your neighbors' gardens. For those with parks adorned with junipers near their gardens, the situation is even more complicated.

Treating your tree at the first sign of symptoms can help avoid significant crop losses. However, it's important to proceed consistently, not just stop at one or two treatments.

The calendar of treatments for pear and juniper against rust is described in the table.

Before the sap begins to flow, all heavily infected branches are pruned back to the healthy core. Shoots with only slight traces of fungus are left alone. Small lesions are trimmed back to the light, clean wood, then disinfected with a 5% copper sulfate solution, treated with Heteroauxin, and sealed with artificial bark or garden pitch.

Preventive measures

Never leave fallen leaves from garden trees over the winter; fallen leaves should be removed throughout the summer, not just in the fall. Burn all plant debris. Periodically thin the tree's crown to ensure adequate ventilation. Spray regularly for preventative treatments.

If you have a juniper growing near your garden, keep a close eye on it. To avoid worrying about rust altogether, spray the juniper along with the pear tree with the same products.

Resistant varieties of pear

There are no pear varieties completely resistant to rust. According to gardeners, the disease is most often observed on Dekanka Zimnyaya, Lyubimitsa Klappa, Bere Ardanpon, and Bosk pears. The following varieties are often considered moderately resistant:

• Sailo;
• Sugar;
• Gulabi;
• Bere Ligel, Giffard and Hardy;
• Early ripening from Trevou;
• Ilyinka;
• Williams.

Be patient if orange spots appear on the leaves of pear trees in your garden; treatment will take a long time. The treatments described above should be repeated several years in a row; in some cases, eradicating the disease can be extremely difficult. If you have juniper trees nearby, preventative spraying will become an annual routine.