Frost

Description

Frost usually occurs when cold, Arctic air penetrates, prevailingly originating from the north or northeast, mainly in winter. It is also caused by radiation in clear, windless weather. Frosts damage trees, especially if they appear suddenly and when the trees are not adapted to low temperatures (e.g. out of winter dormancy). Also rapid alternations of high and low temperatures are very harmful for trees. Frost destroys the tissues, respectively plant organs by preventing their physiological processes. An extreme case is the mortality of trees. It may occur when the water in the soil or in some organs of trees freezes. As a result, its transpiration flow is interrupted or the tissues of the tree organs are mechanically damaged. It is most often in winter or early spring, during sunny weather, especially related to fluctuations and differences in day and night temperatures. The disposition of trees to frost damage depends on the water content in the tissues, or on the concentration of cellular liquids. Occasionally, trees are damaged in spring, i.e. by late frost (April or May) when it mainly affects young, still only partially developed buds or leaves. This often happens in frosty locations, where cold air flows from the wider area.

Endangered trees

Pulling up of seedlings by frost occurs in shallow-rooted trees such as Norway spruce, birches, European beech and ashes. Young, not fully developed shoots of trees, also buds, leaves, flowers are most endangered by frost especially in walnut trees, ashes, black locusts, Douglas fir. Winter bark necrosis occurs in tree species with a smooth bark, especially European beech, Silver fir and European hornbeam. Frost cracks can also occur in tree species with markedly developed wood rays (oaks, elms, European chestnut, horse chestnut).

Damage localization

Frost damage appears on almost all tree organs. Very serious damage occurs especially to the bark of stems and on branches. Frost damage occurs often in young trees on current shoots, buds, leaves and flowers.

Symptom

In forest plantations, established in the autumn with little or no snow cover in winter, surface-frost form may appear, which causes extraction (pushing up) of seedlings. The phenomenon is caused by the expanding the volume of moist soil by freezing, when seedlings are lifted over the ground surface. Early frosts damage especially young, not fully developed shoots. The damage is manifested by wilting and sudden fall of leaves and needles. In older forest stands, the bark cracks, which later falls off. As a result of repeated freezing, so called frost cracks on bark can occur. During long-lasting severe winter frosts, typical frost cores form typically in beech stems.

Tree Species: Black Locust, Beech, Cherry, Oak, Douglas Fir, Chestnut, Hornbeam, Pear, Apple Tree, Maple, Fir, Magnolia, Apricots, Mulberry, Walnut, Horse Chestnut, Spruce

Part of a plant- attacked: Tree trunk, Leaf / Needle, Fruit / Seed

Pest significance: Very harmful

Pest Category: Other

Invasive Species: No

Present in EU: Yes

Seasonal frequency of occurrence