Olle Anderbrant

Effective attraction radius : A method for comparing species attractants and determining densities of flying insects.

The catches of bark beetles (Coleoptera: Scolytidae) were compared between attractive traps releasing semiochemicals and passive traps (cylindrical sticky screens hung, at 10 heights of 0.7–11.5 m, on poles). A central attractive-trap pole was surrounded by three passive-trap poles spaced 50 or 100 m away at the apices of an equilateral triangle. The catches ofTomicus piniperda and other scolytid species on the attractive-trap pole baited with host monoterpenes, or the catches ofIps typographus attracted to synthetic pheromone, were compared to passive trap catches in a Scots pine forest or in a Norway spruce clear-cut, respectively. Information about flight height distributions of the above scolytid species, andHylurgops palliatus, Cryphalus abietis, Pityogenes chalcographus, P. quadridens, P. bidentatus, andTrypodendron domesticum were obtained on the passive and attractive trap poles. A new method is presented for determining the densities of flying insects based on the passive traps dimensions and catch, duration of test, and speed of insect. Also, a novel concept, the effective attraction radius (EAR), is presented for comparing attractants of species, which is independent of insect density, locality, or duration of test. The EAR is obtained by the ratio of attractive and passive trap catches and the dimensions of the passive trap, and thus should correlate positively with the strength of the attractant and the distance of attraction. EARs are determined from catch data ofT. piniperda andI. typographus as well as from the data of previous investigations on the same or other bark beetles.

Gallery construction and oviposition of the bark beetle Ips typographus (Coleoptera: Scolytidae) at different breeding densities

Abstract. 1. The bole of a Norway spruce, Picea abies(L.) Karst., was cut in 25 cm sections and infested in the laboratory with 2 or 8 females/dm2 of Ips typographus (L.) and an equal number of males.

Competition and Niche Separation between Two Bark Beetles: Existence and Mechanisms

The existence and effects of competition as well as niche separation were investigated in a system of two bark beetle species which aggregate on Norway spruce, Picea abies, to feed on and reproduce in the phloem. In this and other bark beetle systems, there is evidence for competition and intra- and interspecific density effects at normally occurring densities, in contrast to the concept of «density vagueness». Under natural conditions adults of the two species showed a spatial niche separation, where the smaller species, Ips duplicatus, occupied only the top of trees. Regression analysis of adult density patterns of each species showed effects of habitat variables and of density of the opposite species. When breeding at naturally occurring densities (representing both low, endemic, and high, epidemic, populations phases), in the same substratum in the laboratory, there was a strong, asymmetric larval competition in favour of Ips typographus

Effects of pheromone trap type, position and colour on the catch of the pine sawfly Neodiprion sertifer (Geoff.) (Hym., Diprionidae)

Two novel easy‐to‐make pheromone traps, a cross‐barrier sticky trap and an open horizontal sticky trap, are described. Both types caught about the same number of male pine sawflies, Neodiprion sertifer, when baited with the synthetic pheromone (2S, 3S, 7S)‐3,7‐dimethylpentadec‐2‐yl acetate. The catch on unbaited cross‐barrier traps was about 17% compared with baited traps, whereas unbaited horizontal traps caught almost no sawflies. There was no difference in catch between horizontal traps positioned close to the stem and at the end of a branch in young Scots pines, but traps on the ground caught less than one tenth of the number caught in traps 1.5 m above ground. The catch in unbaited cross‐barrier traps was dependent on colour, with white being the most attractive.

Survival of parent and brood adult bark beetles, Ips typographus, in relation to size, lipid content and re-emergence or emergence day

ABSTRACT. This study investigated a possible trade‐off between bark beetle reproductive effort and future survival. Parent adult Ips typographus (L.) (Coleoptera: Scolytidae) were collected when they re‐emerged from a laboratory culture after completing their first brood and held at constant temperatures of 4 or 25oC. As a comparison, emerging brood adults were collected and held at 25oC. The longevity of the beetles was related to when they re‐emerged or emerged (measured in days since parent introduction) and to their size (pronotal width), fresh weight and lipid content at collection, by multiple regression analysis. The expression (fresh weight x pronotal width ‐2.6), used as an estimate of lipid content of the living beetles, was significantly correlated (r=0.67, P<0.001) with the actual (extracted) lipid content. At 25oC, fat content was the variable most strongly correlated with survival time in all beetle groups except parent females. In both parent and brood females, re‐emergence or emergence day, respectively, contributed significantly to the explanation of survival time, whereas pronotal width and fresh weight never contributed significantly to the regression equation. At 4oC, fat content was not estimated but, re‐emergence day was negatively correlated with survival time. In conclusion, beetles with high fat content and re‐emerging or emerging early have longer expected survival than beetles leaving the log later or containing less fat. This means that females laying a large first brood might suffer a somewhat higher mortality than females laying a smaller brood.

From where are insects recruited? A new model to interpret catches of attractive traps

Abstract 1 Two new concepts describing the origin of insects caught in an attractive trap are presented.

Sex pheromone of the pine sawfly Diprion pini (Hymenoptera: Diprionidae) : Chemical identification, synthesis and biological activity

The main component of the sex pheromone secretion of femaleDiprion pini L. (Hymenoptera: Diprionidae) from insects collected both in Finland and in France has been identified as athreo-3,7-dimethyl-2-tridecanol (8 ng per female) stereoisomer by GC-MS and synthesis. The secretion also contains lower and higher homologues in small amounts (1–4% of the main component). Combined gas chromatographic-electroantennographic detection showed activity in both natural and esterified extracts (acetates and propionates); the esters of the main component gave the largest responses. The acetates and propionates of the eight stereoisomers of 3,7-dimethyl-2-tridecanol were synthesized from enantiomerically highly enriched (>99% ee) building blocks. The stereochemistry of the main component was established to be (2S,3R,7R)-3,7-dimethyl-2-tridecanol by GC analysis of the natural material. It was purified by liquid chromatography prior to the GC analysis of both its pentafluorobenzoates and its isopropylcarbamates on a non-chiral polar column (ECD) and a chiral column (NPD), respectively. Field tests demonstrated that both the acetate and propionate of the main component (100 μg of each applied on cotton roll dispensers) were active in attracting males, with or without the presence of several of the minor compounds. Experiments with smaller amounts of the acetate and the propionate (1 μg in France and 50 μg in Finland) demonstrated that the propionate was more active than the acetate, and that it also caught more males than a blend of the two compounds.

Pheromone related-compounds in pupal and adult female pine sawflies, neodiprion-sertifer, of different age and in different parts of the body

Abstract The pine sawfly pheromone precursor 3,7-dimethyl-2-pentadecanol (diprionol) was quantified by gas chromatography in different body parts of virgin female Neodiprion sertifer . About one-third of the total amount (approx. 10 ng per female) was found in each of head + thorax, abdominal segments 1–3, and the remaining abdomen. Diprionol was also found in the respective parts of pupae, but in lower amounts. This suggests that at least the final steps of the pheromone biosynthesis take place in many parts of the body, possibly in the cuticle. The diprionol content remained relatively constant over the whole lifetime of virgin females. By using coupled gas chromatography-electroantennogram detection three active compounds in the acetylated female extract were observed. These corresponded to the pheromone, (2 S ,3 S ,7 S )-diprionyl acetate, and its homologues with the chain shortened by one and two carbons respectively, as determined by gas chromatography-mass spectrometry. In addition, the homologue having a chain elongated by one carbon was found. The homologues occurred in amounts of 2–5% of the diprionyl acetate. When synthetic homologues were tested in the field, alone or in combination with diprionyl acetate, they were not behaviourally active to male sawflies, despite their electroantennogram activity. A threo -isomer of diprionol, most likely (2 S ,3 R ,7 R ), was present in the females in amounts less than 0.5% of the (2 S ,3 S ,7 S )-content. The acetate of this threo -isomer is known as both synergist and inhibitor to the (2 S ,3 S ,7 S )-isomer. trans -Perillenal was found in the abdominal segments 1–3 of both males and females and its possible biosynthetic relationship to diprionol is discussed.

Field response of the pine sawfly Neodiprion sertifer to the pheromone (2S, 3S, 7S)-diprionyl acetate and its stereoisomers

All eight optical isomers of 3,7‐dimethyl‐2‐pentadecanyl acetate (diprionyl acetate), of high optical purity (>97.4%), were tested for a behavioural activity on male pine sawflies, Neodiprion sertifer (Geoffr.) (Hymenoptera: Diprionidae), in northern Europe. Males were strongly attracted to (2S, 3S, 7S)‐diprionyl acetate. Addition of more than 0.1% of the (2S, 3R, 7R)‐isomer reduced the catch and above 2% the attraction was completely inhibited. Contrary to what has been reported for North American and Japanese populations, so significant synergistic effect of small amounts of the (2S, 3R, 7R)‐isomer could be demonstrated. The effects of addition of the other six optical isomers alone or in combinations, were also studied, but none was found to be a synergist. The (2S, 3R, 7S)‐isomer had a weak inhibitory effect, and completely inhibited the attraction to the (2S, 3S, 7S)‐isomer when applied in about equal amounts as the attractant. In some cases a reduction in catch was noted when other isomers were tested, but this could be attributed to the very small amounts of the inhibitory (2S, 3R, 7R)‐isomer present in these isomers.

A model for the temperature and density dependent reemergence of the bark beetle Ips typographus

A model is presented that describes the reemergence of parent spruce bark beetles, Ips typographus, based on breeding density and temperature conditions. Laboratory data obtained at one constant temperature provide the distribution of reemergence time and different combinations of threshold temperatures and degreedays (°D) at mean reemergence. Of these combinations, 167.71 °D above 7.5 °C gave the best correspondence between model prediction and field data obtained from densely infested standing trees. The model was in good agreement with the reemergence pattern found for two groups of infested logs under different temperature conditions when adjusted for the lower breeding density. The applicability of the model in the study of bark beetle reproductive biology and in forest management is discussed. The method used to construct the model should be useful in developing other models for poikilothermic processes.