Cold gun Armillaria sp. syn. Armillariella sp.

LEVEL

Spread worldwide.Capable of infecting all woody plants of all ages. It is one of the most dangerous causal agents of root rot in our forest trees.

VEGETABLE

Annuals, with a leg up to 15 cm long and a brownish cap up to 10 cm in diameter, covered with darker scales. Underside with whitish bracts, ring on foot. Often grow in a shrubby clump (legs grown together at base) on stumps, roots, trunk and bark fragments. The fruiting bodies occur from late summer to frost.

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Cold rot is a semi-parasitic pest, causing white rot in the lower part of the trunk and in the roots, which can result in tree breakage. The rot is brownish in colour, with characteristic black outlines. Sometimes the fungus destroys the cambium layer under the bark, causing rapid desiccation of the tree (cambium killer). The fungal canker continues to grow for many years in stumps and in roots left in the soil, and can infect young trees planted in the same place.

It spreads by airborne spores falling on the exposed tree surface, but also in the soil ( about 0.5 m per year) either by shrivelled roots from diseased trees to whole trees or by rhizomorphs characteristic of cold oak through the soil.

In conifers, the disease is indicated by yellowing of the branches, loss of root growth, resin flow around the root collar; in deciduous trees, the foliage thins first and dry branches appear in the shoot. A white foliose fungal scale develops under the bark of the bark of the infected tree, and later rhizomorphs grow on the bark - white on the inside, shiny blackish-brown 0,25-4 mm thick, reticulated, branched fungal strands.

According to the system used in the past, one species in Europe was the common cold-faced pheasant (A.mellea). It is now divided into several very similar-looking fungal species, which do not interbreed and are pathogenic to varying degrees. Four of these occur in Estonia.

The black cold louse(A. ostoyae, syn. A. obscura) is the most common and probably the most dangerous; it produces root rot mainly on pines, less frequently on other trees.

Northern(A.borealis) and spotted knotweed(A-cepistipes) sometimes attack spruce trees in forests with spruce-root aphid, in parks only previously weakened trees.

The Mugul-cucumber fungus(A.gallica, syn. A. bulbosa, A.lutea occur very rarely.

The common (honeydew) cold louse (A. mellea) is an aggressive pest, but fortunately with a more southern distribution. The cold louse is similar to the armoured louse (Pholiota squarrosa), but has larger and more turgid scales on both the foot and the hood.