Semiochemical diversity diverts bark beetle attacks from Norway spruce edges

• The semiochemical diversity hypothesis (SDH) states that interference with host-selection from non-host volatiles (NHV) is an important mechanism for associational resistance. Inhibition of bark beetle attraction to point sources by non-host volatiles (NHV) is well established and might be a signal serving in host-selection also at the habitat scale. In forests dominated by Norway spruce in middle and northern Europe (N Slovakia 2006 & 2007, SE Sweden 2007), we applied a blend of NHV and verbenone, released from dispensers fixed at 2 and 6 m height at forest edges with high Ips typographus populations. In Slovakia, three different doses (0.2–0.7 dispensers/m forest edge) were tested in 20-tree zones of spruce stand edges. The Swedish experiments used only the middle dose. In Slovakia, there was high tree mortality but dispensers with the anti-attractants reduced killed trees in a dose-dependent manner. The reduction in tree killing ranged from 35 to 76% compared to untreated zones. Regression analysis of relative tree kill on log dispenser density was highly significant (R2ADJ= 0.34, corresponding effect size d≈ 0.98). In Sweden, with lower beetle populations, most attacks (99%) were found outside the experimental areas, with high attack rates (15 trees/ha) in a range of 15–30 m from treated groups, indicating an active inhibitory radius exceeding the previous estimates. The SDH as a functional aspect of biodiversity was tested by converting spruce monocultures into an artificial semiochemically mixed forests. The use of NHV provides the only non-insecticidal method of direct protection of conifer forests. The demonstrated principle of protection is still too expensive for area-wide use, but viable for high-value areas (nature reserves). Further development of push–pull strategies or area-wide applications may prove more cost efficient. In the long-term, the only sustainable approach is a forest landscape of mixed habitats.

Ämnesord

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Skogsvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Forest Science (hsv//eng)

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Landskapsarkitektur (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Landscape Architecture (hsv//eng)

LANTBRUKSVETENSKAPER  -- Annan lantbruksvetenskap -- Miljö- och naturvårdsvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Other Agricultural Sciences -- Environmental Sciences related to Agriculture and Land-use (hsv//eng)

Nyckelord

bark beetle control

non-host volatiles

Forestry

Skogsskötsel

Ecological chemistry

Ekologisk kemi

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