Threats

Pine bark beetle/Hylastes angustatus

Pine bark beetle/Hylastes angustatus
Hylastes angustatus (Herbst, 1793)

Bostrichus angustatus Herbst 1973

Hylastes scandinavicus Lekander 1965

Ophiostoma ips, O. pluriannulatum, O. stenoceras, Leptographium lundbergii, L. serpens, Ceratocystiopsis minuta (Zhou et al. 2001).
Wood boring

Of the three pine infesting bark beetles introduced into South Africa, Hylastes angustatus tends to be the most problematic. Severe infestations of this species in newly planted plantations can result in up to 50% seedlings loss due to girdling caused by the under bark boring activities of the beetles and their larvae (Tribe 1992).

Attracted by the volatiles produced by damaged pine, H. angustatus is typically found boring in felled logs or discarded branches within the plantation and is considered a secondary bark beetle of stressed trees. Additionally, in some instances, the beetles can also be found infesting the lateral roots of growing pines and are known to infest trees below ground level. This indiscriminate boring and breeding of the beetles in discarded material within the plantation leads to population booms, from where the beetles spread into newly planted plantations, attracted by volatile cues produced by the seedlings due to post planting stress (Erasmus & Chown 1994).

Hylastes angustatus is a dark brown to black beetle that ranges from 3-4 mm in size. The legs and antennae are often lighter in colour than the body, appearing reddish-brown. The pronotum contains even and dense punctures, whereas the elytra is coarsely punctate-striate from the base to the edge of the declivity.

In South Africa, H. angustatus is reproductively active from mid-August until early April. The species is most considered a pest of summer rainfall regions as dispersal is timed with the occurrence of rain. However, with later rainfall occurring in the winter rainfall areas, the species is becoming more problematic in the Southern Cape. Due to the long active period of the species, up to three generations can occur in winter rainfall regions per season, and up to five generations can occur in summer rainfall regions (Tribe 1991).

Primarily relies on good silvicultural practices including the removal of slash and pine debris from plantations to prevent the build-up of beetle populations and reducing the levels of seedling damage during planting to prevent the production of volatile cues that attract the beetles.

1957 (Schedl 1957)
Eastern Cape, KwaZulu-Natal, Limpopo, Mpumalanga, Western Cape
Various species of Pine
Europe (Reay & Walsh 2001, El Khoury et al. 2019)

Image

Lateral view of Hylastes angustatus adult (scale = 1mm)

El Khoury, Y., Binazzi, F., Nemer, N., Noujeim, E., Tarasco, E., Roversi, P.F. & Pennacchio, F. (2019) Bark beetles (Coleoptera Curculionidae Scolytinae) associated with Pinus pinea in Lebanon: New records with remarks on their ecology, distribution and potential threat for forest stands. Redia, 102 121-128.

Erasmus, M.J. & Chown S.L. (1994) Host location and aggregation behaviour in Hylastes angustatus (Herbst) (Coleoptera: Scolytidae). African Entomology, 2 (1), 7-11.

Reay, S.D. & Walsh, P.J. (2001) Observations of the flight activity of Hylastes ater and Hylurgus ligniperda (Curculionidae: Scolytinae) in Pinus radiata forests in the central North Island, New Zealand. New Zealand Entomologist, 24 (1), 79-85.

Schedl, K.E. (1957) Bark- and timber-beetles from South Africa. Annals and Magazine of Natural History, 10 (110), 149-159.

Tribe, G.D. (1991) Phenology of the important Coleopterous pests of pine forests in the Western Cape, South Africa. Thesis.

Tribe, G.D. (1992) Colonisation sited on Pinus radiata logs of the bark beetles, Orthotomicus erosus, Hylastes angustatus, and Hylurgus ligiperda (Coleoptera: Scolytidae). Journal of the Entomological Society of South Africa, 55(1), 77-84.

Wood, S.L. & Bright, D.E. (1992) A Catalog of Scolytidae and Platypodidae (Coleoptera), Part 2: Taxonomic Index. Volume B. Great Basin naturalist memoirs., 13 835-1557.

Zhou, X.D., De Beer, Z.W., Wingfield, B.D. & Wingfield, M.J. (2001) Ophiostomatoid fungi associated with three pine-infesting bark beetles in South Africa. Sydowia, 53 (2), 290-300.