Claude Géri

The Pine Sawfly in Central France

The pine sawfly, Diprion pini Linne (Hymenoptera, Diprionidae), is widespread from the British Isles to the Soviet Union and from North Africa to Finland. The family Diprionidae includes about 85 species living exclusively in the coniferous forests of the Northern Hemisphere. The species are assumed to be very close to primitive forms derived from panorpoid ancestors in the Permian 70,53 Many of these species belong to the genera Diprion and Neodiprion that differentiated in the subfamily Diprioninae, in the Palaearactic and Nearctic continents, respectively. In the Old World, the subfamily is represented by the genera Diprion, Gilpinia, Microdiprion, Macrodiprion (essentially in Europe), Prionomeion (North Africa), and Nesodiprion (Asia) and by a few species of American origin, such as Neodiprion sertifer Geoffroy.

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.

Relationship of Scots pine clone characteristics and water stress to hatching and larval performance of the sawfly Diprion pini (Hymenoptera : Diprionidae)

Abstract Most Symphyta are phytophagous and lay their eggs in the host plant in contact with the plant tissue. We tested the hypothesis that Diprion pini L. egg hatching and larval survival vary between Scots pine clones with particular foliage characteristics. We also tested the influence of water limitation on hatching rates. Larval survival and hatching rate of D. pini eggs differed significantly among Pinus sylvestris L. genotypes and they were not correlated. We confirmed that the presence of taxifolin, a phenolic compound, and quantity of 3-carene were correlated with low larval survival. Foliage analysis showed an inverse relationship between hatching rate and dry matter content of foliage. The hatching rate on a tree varies, according to needle water content. This suggests that the success of egg development might be important for the population dynamics of D. pini.

Electrophysiological and morphological characteristics of pheromone receptors in male pine sawflies, Diprion pini (Hymenoptera, Diprionidae), and behavioral response to some compounds

Electrophysiological And Morphological-Characteristics Of Pheromone Receptors In Male Pine Sawflies, Diprion Pini (Hymenoptera, Diprionidae), And Behavioral-Response To Some Compounds

Preference and performance of the sawfly Diprion pini on host and non‐host plants of the genus Pinus

The sawfly, Diprion pini L., is a pest of Pinus in Europe and is mainly found on P. sylvestris L. and P. nigra laricio Poiret. The relative importance of female oviposition capacity and behaviour, egg development, and larval survival on a new host plant was measured on 11 pine species. Five were natural host plants and six non‐host plants, five of which are not indigenous to Europe. Oviposition choice tests showed that females discriminated between the pine species. Egg and larval development also differed between pine species. However, the female choice was not linked with hatching rate and larval development. Results of biological tests clearly indicated that there were different response patterns of D. pini life stages in relation to pine species, and these patterns were the same with insects of four different origins. We discuss the importance of each potential barrier to colonisation of a new host.

Release of sex pheromone and its precursors in the pine sawfly Diprion pini (Hym., Diprionidae)

Summary.The first identification of a sex pheromone of a pine sawfly (Hymenoptera, Diprionidae) dates back almost thirty years. Since then, female-produced pheromones of over twenty diprionid species have been investigated by solvent extraction followed by separation and identification. However, no study has shown what the females actually release. Collection of airborne compounds using absorbtion on charcoal filter as well as solid phase microextraction (SPME) followed by analysis employing gas chromatography combined with mass spectrometry (GC-MS), revealed an unusual system in Diprion pini, in which the pheromone precursor alcohol, 3,7-dimethyl-2-tridecanol, is released together with acetic, propionic, butyric and isobutyric acids. The corresponding acetate, propionate and butyrate esters of 3,7-dimethyl-2-tridecanol were also found in the samples. All esters were electrophysiologically active, and the propionate and isobutyrate were attractive in trapping experiments. Based on these and earlier reported results, it seems that at least in part of its range, the pheromone response of D. pini is not very specific with regard to the functional group, as long as this is an ester.

Variation in the suitability of Pinus sylvestris to feeding by two defoliators, Diprion pini (Hym., Diprionidae) and Graellsia isabellae galliaegloria (Lep., Attacidae)

Abstract: Feeding bioassays were conducted on several Pinus sylvestris clones to establish if there were any differences in suitability for two pine defoliators: the sawfly Diprion pini L. (Hym., Diprionidae), which causes considerable damage in Europe, and the rare and protected moth Graellsia isabellae galliaegloria Oberthür (Lep., Attacidae). There were significant differences in survival, weight, sex‐ratio and female fecundity of D. pini on Scots pine clones. However, sawfly survival appeared to be the most stable variable in time and three clone categories were revealed by conducting feeding bioassays on 16 clones. The survival of G. isabellae galliaegloria until the formation of the chrysalis was significantly different among clones. It varied from 35 to 75% but no clear clone category was distinguished. The two clone classifications according to insect survival showed differences. In particular, one unsuitable clone for D. pini development appeared to be favourable to moth development. The 3‐carene richness of foliage was significantly linked with sawfly survival and the monoterpene composition of foliage was not linked with G. isabellae galliaegloria survival.

Oviposition preference and larval survival of Diprion pini on Scots pine clones in relation to foliage characteristics.

1 When laying eggs, adult female Diprion pini discriminated between clones of Scots pine, Pinus sylvestris.

The chromosomes of Diprion pini and D. similis (Hymenoptera: Diprionidae): implications for karyotype evolution

Earlier cytological investigations characterize the family Diprionidae with a modal chromosome number of seven. This study shows that Diprion pini and D. similis have 14 acrocentric chromosomes (n=14 for haploid males and 2n=28 for diploid females). In D. pini, rRNA genes are located on the satellite and the round short arm of the chromosome carrying this segment. We studied six populations with no evidence of chromosomal polymorphism at the species level. Our results disagree with those published previously and reopen the question of karyotype evolution. Chromosome morphology, ISH and C-banding results support the hypothesis of chromosome number doubling by centric fission and not by polyploidization, followed by the growth of short arms by means of pericentromeric DNA amplification.

Chromosomal location of rRNA genes in Diprion pini detected by in situ hybridization

Abstract Diprion pini belongs to a small family of sawflies with n = 7 as the modal chromosome number. This species has 14 acrocentric chromosomes and one carries a satellite. In situ hybridization to mitotic chromosomes of a Drosophila rDNA probe was carried out according to two protocols. The biotinylated probe was detected with peroxidase-conjugated extravidin and diaminobenzidine or with fluorescein-conjugated extravidin (FISH). These two techniques showed that only one chromosome per haploid complement responds to the probe used. The centric fission hypothesis is consequently more likely than polyploidization in order to explain the chromosome number doubling in D. pini . The sites of probe hybridization are located on the satellite and its carrier short arm, which are heterochromatin-rich. The propensity of rDNA and heterochromatin for self duplication and accretion most likely created the satellite and the short arms. This process is also known to be one of the mechanisms by which extra segments may arise.