Morphology. Last instar larvae are up to 5 cm long with 5 pairs of blue and 6 pairs of red warts on the back. The colour of the body is highly variable (to compare here). Male and female moths have different appearence which was reflected in the species name 'dispar'. Female moths have dirty-white wings with four unclear black cross belts. Th wing span is 40-80 mm. Male moths have browny-grey wings with wide dark stripes; wing span is 30- 60 mm.
Host species. Birch, larch, aspen, willow, pea shrub, bird cherry, oak, and some other species of decidous trees and shrubs.
Life cycle. Gypsy moths fly in July-August. Both males and females fly are able to fly in Siberia. In Siberia and Zabaikalie females lay egg masses in crevices, on rocks, mound tops, and slopes of river valleys. In the absence of these features females lay eggs on the boles of old trees (not necessary on host plants) usually near a stem base. In Far East females lay eggs in crowns of deciduous trees on the lower side of leaves which fall down later. In southern Siberia and Zabaikalie first larvae hatch in the middle of May. They can be spread far away by ascending air flows with the help of their aerophorous hairs and silk thread. Larvae feed during 40- 45 days and go through 4-6 (males) or 5-7 (females) instars. They pupate in crowns of their host trees. The pupa phase lasts up to 15 days.
Black Fir Sawyer Beetle - Monohamus urussovi Fish. (Coleoptera: Cerambycidae)
Morphology. Large (18-38 mm long) black beetles with white downiness of the end of forewings. Antennas of a female are not longer than its’ body, the antennas of a male are much longer than its’ body. Larvae are apodal, yellowish- white. They inhabit in wood galleries made by them in tree boles. They have up to 4 (males) or 6 (females) instars, reaching 6-7 cm long.
Food tree species. All the coniferous species fit for this purpose, also birch and aspen stems.
Distribution. This species is met from Poland and Finland to the Pacific ocean, it inhabits the islands of Sakhalin and Kurily.
Life cycle. Beetles fly from May to September having a peak of density in July. After mating the female usually gnaws an oblong cavity in the tree bark and lays one, seldom 2-3 eggs under the bark. A larva of the first instar eats cambium. Beginning from the second year and up to the pupation it makes galleries in wood. Usually larva overwinters twice and pupates in spring of the third calendar year of its’ life. A pupa lies some weeks in a specially gnawed chamber near the stem surface. While hatching a beetle makes an ideally round hole with the diameter of 6-12 mm and moves outside. Under favorable climatic conditions (Kazakhstan, Primoriye) development of a beetle can be finished in a year. In Siberia a part of specimens develops three (four calendar) years. In this case the larvae overwinters three times.
Impact Assessment. Beetles feed on thin bark and cambium from fir shoots. During nourishment and laying eggs the beetles infect trees with spores of phytopathogenic fungi of the genera Ophiostoma and Leptographium – the source of the blue stain disease.
The developing fungus kills tiny branches on the periphery of the crown, weakens the tree and reduces resin flow. This makes oviposition and larvae development of the beetle more successful. To our knowledge fungi are pathogenic only for fir species. In Siberia, M.urussovi ifs frequently found on birched (Betula) and aspens (Populus), but
causes little damage to it.
M.urussovi is one of the most destructive pests of firs in Northern Asia. The pest increases its number in fir forests damage by defoliating insects, fires and windfalls. Having infested the damaged parts of the forest, the beetle population becomes dense enough to attack, weaken and kill healthy stands. By attacking healthy fir stands dense beetle population can maintain outbreak level indefinitely, causing the death of forests over enormous areas. In the late 1950’s in the Tomsk Oblast’ (Western Siberia), the pest destroyed 2 million square meters of fir wood stock. This caused the collapse of forest enterprises in that region for years and previously planned construction of a railway was delayed significantly slowing the industrial development of the whole area. In 1971-1976, an outbreak of M.urussovi destroyed 300,000 hectares of fir forest in Krasnoyarsk Kray in the Central Siberia.
