Open access publications in the SLU publication database

Abstract

We searched for antifeedant activity in predominantly non-host woody plants to find new compounds for seedling protection of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) against feeding by pine weevil Hylobius abietis. In total, 38 species was tested in an assay where the insects are let to feed on the bark on a short stump of wood. Among the best candidates was linden (Tilia cordata). The bark was extracted and fractioned. Two fractions showed antifeedant activity in a micro feeding assay. Nonanoic acid was identified in both of these fractions. Subsequent testing in the micro feeding assay showed that nonanoic acid possessed strong antifeedant activity against H. abietis adults. Structure-activity and possible formulations for field application of nonanoic acid was investigated in laboratory and field by variation of the nonanoic acid molecular theme. Alkanoic acids of varying chain length from C6 to C13 and corresponding branched acids methyl-substituted in 2-position was tested. Derivatives of higher and lower volatility, restricted to straight chain C9, included 1-nonanol, nonanal, sodium nonanoate, and nonanoic anhydride were also tested. The C7 to C10 chain-length straight-chain acids were all active. Branched acids were active at +1 C higher molecular mass. Phytotoxic side effects occurred when nonanoic acid was tested in field, but an inactive wax layer, applied on the stem before the formulation, reduced the side effects. Bark extract from ten different tree species, which were earlier identified as non-preferred by the pine weevil were tested. One active extract was further fractionated. The content of active and inactive extracts was investigated by GC-MS.