Hylastes

Erichson, 1836

Hylastes is a of in the , comprising over 90 . Members are primarily associated with coniferous , particularly pines and spruces, where they breed in stumps, roots, and stressed or dying trees. Several species are economically significant as of fungal causing tree mortality. The genus has a fossil record extending to the Eocene, with Hylastes perkovskyi described from Rovno amber.

Hylastes porculus by (c) skitterbug, some rights reserved (CC BY), uploaded by skitterbug. Used under a CC-BY license.

Hylastes opacus by (c) Donald Hobern, some rights reserved (CC BY). Used under a CC-BY license.

Hylastes gracilis by (c) Trevor Van Loon, some rights reserved (CC BY), uploaded by Trevor Van Loon. Used under a CC-BY license.

Pronunciation

How to pronounce Hylastes: /hɨˈlæstiːz/

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Habitat

Associated with coniferous forests; breed in stumps, roots, and lower boles of dead, dying, or stressed conifers. Some species dig through soil to reach root systems. Hylastes nigrinus is strongly associated with Douglasfir, while other species occur in pine-dominated systems.

Distribution

Widespread in the Northern Hemisphere. Hylastes opacus is to the Palearctic region and to North America. Hylastes nigrinus occurs in western North America. Records exist from Denmark, Norway, Sweden, and the United States (Vermont, New York, California, Oregon).

Seasonality

Hylastes nigrinus shows peak and in late April and early May in western Oregon, with activity strongly temperaturedependent (seldom below 16°C or above 24°C) and influenced by light intensity (peaking 300–1200 ft-c during late afternoon or early evening).

Diet

Phloem and inner bark of conifer roots and stumps. Feeding occurs on dead, dying, or stressed material; maturation feeding documented on small roots of dead old trees and on roots of young replanted trees weakened by transplant stress.

Host Associations

Pinus taeda (loblolly pine) - Hylastes is one of the most common observed in this ; associated with Leptographium fungal transmission
Pseudotsuga menziesii (Douglas-fir) - Primary for H. nigrinus; breeding in roots and stumps of killed and cut trees
Pinus sylvestris (Scots pine) - for H. opacus and H. cunicularius
Pinus resinosa (red pine) - for H. opacus
Pinus radiata - Preferred for H. ater feeding
Picea abies (Norway spruce) - Main for H. cunicularius; readily accepted though sometimes secondary to pine
Leptographium terebrantis - Hylastes , primarily H. nigrinus, potentially this to loblolly pine roots
Leptographium serpens - Associated with Hylastesmediated transmission to loblolly pine
Verticicladiella wageneri - H. nigrinus demonstrated to this to Douglasfir seedlings

Life Cycle

Hylastes nigrinus: galleries initiated in June, eggs laid from late June; five larval ; majority complete development in one year; and fullgrown overwinter in galleries. H. opacus: breeds in stumps and roots of dead or dying .

Behavior

use volatiles as orientation cues. Hylastes opacus attracted to nonanal, ethanol, (−)-α-pinene (separately, without ), and spruce turpentine. Hylastes nigrinus attracted to α-pinene, β-pinene, and Douglasfir resin; digs through soil to reach roots. Hylastes cunicularius aggregates at host material or independent of sex; no evidence of ; finds hidden host material by active orientation; prefers root sections over stem sections; fresh cuts enhance attraction.

Ecological Role

Primary and secondary colonizers of stressed, damaged, or dead conifers; contribute to decomposition of woody debris. Some act as for pathogenic , linking activity to forest health issues including black stain root and loblolly pine decline. levels increase in thinned stands, potentially elevating disease risk.

Human Relevance

Several are forest pests of economic concern. Hylastes species Leptographium causing mortality in loblolly pine, an emerging forest health issue in the southeastern United States. Hylastes opacus is an species in North America. Hylastes ater is a pest requiring integrated control approaches. Thinning operations increase activity and associated risk.

Similar Taxa

DendroctonusBoth are scolytine breeding in conifers; Hylastes often breed in material killed by Dendroctinus (e.g., H. nigrinus in Douglasfir killed by D. pseudotsugae). Dendroctonus species typically attack living trees and have more pronounced gallery patterns, while Hylastes on roots and stumps.
TomicusBoth use pine and respond to similar host volatiles; Hylastes opacus was unexpectedly captured during experiments targeting T. piniperda attraction. Tomicus typically attack shoots and trunks of living pines, whereas Hylastes species specialize in belowground portions of dead or stressed trees.

More Details

Fossil Record

Hylastes perkovskyi, described from Eocene Rovno amber, indicates the evolved by the Eocene epoch. as a group have fossil evidence extending to the early .

Natural Enemies

Hylastes nigrinus larval in western Oregon experienced heavy mortality from Medetera vidua () during fall 1965.

Competitive Interactions

Hylastes nigrinus shares stumps and roots with multiple , , , and ; data documented for competing species in Douglasfir systems.