Identification and Control Methods of the Spruce Root Bark Beetle

The spruce root bark beetle (Hylastes cunicularius Erichson) belongs to the order Coleoptera, family Scolytidae. In China it is distributed in ** and Sichuan, mainly damaging spruce, and is especially severe on artificially regenerated seedlings.

Damage characteristics: it feeds on the roots of spruce seedlings and attacks freshly cut stumps.

Morphological characteristics: adult body length about 4.5mm, dark brown, slightly glossy, with sparse bristles. The frons is narrow and long, covered with flat, shallow, dense punctures each bearing 1 hair; the lower half of the frons is low and flat, the upper half protrudes, with the highest point between the eyes. The pronotum is about as long as wide; the dense punctures often join into rows with narrow intervals, or protrude as granules without intervals, and each puncture bears 1 short hair. The elytra are 2.7 times the length of the pronotum and 1.9 times the combined width of the two elytra; the round punctures in the puncture striae are arranged regularly, and the puncture centers are hairless; the fine hairs on the interstriae gradually lengthen, the small bristles are obvious at the elytral base, and after the middle of the elytra they become large bristles, 3-4 in transverse rows, with no erect hairs.

Occurrence pattern: in the western Tianshan Mountains there is 1 generation per year, overwintering as adults boring in the phloem of the lateral roots of fresh stumps on cutting sites. Before mating and laying eggs in June, the adults fly away from the overwintering site to feed on the roots of spruce seedlings for supplemental nutrition, then invade fresh stumps to feed, mate and lay eggs. Because lateral roots of old stumps rot and are no longer invaded, spruce seedlings regenerated on new cutting sites suffer severe damage, while those on old cutting sites suffer light or no damage.

Control methods

(1) Strictly implement quarantine to prevent the spread of the pest via seedlings and timber.

(2) Strengthen forest management.

Create mixed forests, and combine with tending and cutting to enhance tree vigor; pay attention to forest sanitation, and remove pest-infested trees and wind-broken trees; under the premise of good sanitary conditions, cut small-diameter wood in mid-April, set up trap logs to attract and kill the pest, and then carry out debarking treatment uniformly.

(3) Protect natural enemies such as ground beetles, parasitic wasps and woodpeckers.

(4) Chemical control.

From the end of May to the beginning of July, during the peak period of adult flight and invasion, spray the branches and trunks of living standing trees with a 200-fold dilution of 2.5% deltamethrin ointment or a 500-fold dilution of 30% cypermethrin toxic paste to control the adults.

Commonly used pesticides: deltamethrin, cypermethrin.