Identification and Control Methods of the Spruce Sawyer Beetle

The spruce sawyer beetle (Monochamus urussovi Fisher), also known as the spruce black longhorn beetle, belongs to the order Coleoptera, family Cerambycidae. In China it is distributed in the Northeast, Inner Mongolia, Hebei, Shandong, Jiangsu, Shaanxi and other places. It mainly damages Picea koraiensis (Korean spruce), Picea jezoensis (Jezo spruce), Abies nephrolepis (Khingan fir) and others, and is a major pest of coniferous timber in northern China.

Damage characteristics: the larvae damage felled trees, weakened standing trees, wind-thrown trees and logs in timber yards, forming thick galleries; the adults gnaw the tender bark of small branches of living trees.

Morphological characteristics

Adult body length 21-33 mm. Body black, with a dark green or bronze sheen. The antennae of the male are about 2-3.5 times the body length; the antennae of the female are slightly longer than the body. The pronotum has 3 indistinct tubercles, and the lateral spines are well developed. The scutellum is densely covered with short grayish-yellow hairs. The base of the elytra is densely covered with granular punctures and sparse short fine hairs; toward the end of the elytra the punctures gradually become flat and the hairs denser, and the end is entirely covered with hairs, appearing earth-yellow; there is 1 transverse impression at the front 1/3 of the elytra. The base of the elytra is widest in the male and gradually widens posteriorly. In the female the two sides of the elytra are nearly parallel, with grayish-white hair patches in the middle gathered into 4 blocks, but often with irregular variation.

Egg kidney-shaped, length 4.5-5 mm, width 1.2-1.5 mm, yellow-white.

Larva: mature larva body length 37-50 mm, head capsule width 3-5.9 mm, milky yellow. Head rectangular, rounded at the posterior end. About 2/3 retracted into the thorax. The prothorax is the most developed, its length equal to the sum of the other 2 thoracic segments; the pronotal plate has a convex reddish-brown patch. The dorsal and ventral surfaces of the thorax and abdomen have ambulatory ampullae; the dorsal ampullae have 2 transverse grooves, with annular grooves at both ends of the transverse grooves; the ventral ampullae have 1 transverse groove, with short backward-slanting grooves at both ends of the transverse groove.

Pupa body length 25-34 mm, white to milky yellow; the pronotum has well-developed lateral spines; the abdomen shows 9 segments.

Occurrence pattern: in the Greater Khingan Mountains forest region of Inner Mongolia it generally has 2 years 1 generation or 1 year 1 generation, overwintering as large and small larvae. Adults begin to emerge in early June; the oviposition period is from late June to early September, with the peak oviposition period from late July to early August; larvae begin to hatch in early July and gnaw the phloem and outer sapwood under the bark, with the damaged part being irregular in shape. After about one month, the larvae begin to bore vertical galleries into the xylem, and by the end of September they bore into the galleries to overwinter. In May of the second year they bore out from the xylem to the phloem to feed; by mid-July the larvae mature, bore into the xylem again to make galleries, and build pupal chambers at the ends of the galleries. The larvae have 6 instars in total. The mature larvae overwinter again in the pupal chambers and pupate in early May of the third year. After emergence, the adults remain in the pupal chambers inside the trunk for about 1 week, then bore out through the emergence holes; the emergence holes are about 8 mm in diameter.

Adults must undergo supplemental nutrition, otherwise they cannot reproduce; therefore during the mass emergence period a large number of spruce black longhorn beetle adults gather in the crowns of spruce trees. Females begin to lay eggs 10-21 days after emerging and flying out. After mating, the female finds a suitable trunk and begins to bite a linear notch, then turns around and inserts the ovipositor, laying 1-2 eggs each time, and can lay up to 14-58 eggs in a lifetime, averaging about 30. The galleries in the xylem are of three types: horseshoe-shaped, arc-shaped and straight. It mainly damages fallen trees and weakened trees, and can also damage tender branches, especially spruce needles, during the adult supplemental nutrition period.

Control methods

(1) Strictly implement quarantine, and strictly prohibit the spread and diffusion of insect-carrying logs and wood.

(2) Strengthen forest management.

Create mixed forests, strengthen tending, and enhance tree vigor; carry out timber harvesting during the period when adults are inactive, and transport summer-harvested logs out of the forest in a timely manner; peel logs in timber yards promptly to reduce suitable hosts for the longhorn beetle.

(3) Protect natural enemies such as the parasitoid beetle and woodpeckers.

(4) Chemical control.

① When it occurs on a small area, use a punching machine to inject strongly systemic drugs such as Dali Shi for control.

② During the adult stage of the longhorn beetle, especially when adults are feeding for supplemental nutrition at the peak emergence period, carry out control, mainly by spraying Green Weilei on the trunk or, during supplemental nutrition, spraying the host tree crown and trunk.

③ Pest-infested wood should be promptly treated for pest elimination; aluminum phosphide or methyl bromide can be used for tent fumigation, or Green Weilei can be sprayed from above and at both ends of the log stack for control.

④ When there is waterlogging, drought, fire, or poor growth of large areas of forest, spray insecticides such as fenthion, fenitrothion, malathion or deltamethrin during the adult activity period to kill them.

Commonly used agents: fenthion, fenitrothion, malathion, deltamethrin, Green Weilei, aluminum phosphide, methyl bromide.