P. Menassieu

Terpene variations in maritime pine constitutive oleoresin related to host tree selection byDioryctria sylvestrella RATZ. (Lepidoptera: Pyralidae)

Gas chromatographic analysis of the volatile terpenes of the wood oleoresin of maritime pines showed that the relative proportions of terpenes within the same tree did not vary according to sampling height and date. Pruning and tree vigor did not affect terpene profiles, but oleoresin composition varied widely from tree to tree. The trees attacked byDioryctria sylvestrella contained a significantly higher percentage of limonene, longipinene, and copaene, and a discriminant analysis, using the relative percentage of six terpenes, significantly separated infested and uninfested trees. The olfactory sensitivity of adult moths to a series of 20 volatile chemicals, including maritime pine oleoresin components, was evaluated with the electroantennogram method. Both sexes were sensitive to monoterpenes, oxygenated terpenoid compounds, and oleoresin samples. The use of terpenes as host attractants and biochemical markers for resistance toD. sylvestrella is discussed.

Identification of the sex pheromone of the maritime pine scale Matsucoccus feytaudi.

(2E,4E)-4,6,10-trimethyl-2,4-dodecadien-7-one and (2E,4Z)-4,6,10-trimethyl-2,4-dodecadien-7-one have been identified mostly through 2D NMR and MS/MS techniques as primary and secondary components of the sex pheromone of Matsucoccus feytaudi.

Non-Host Volatiles Disrupt the Response of the Stenographer Bark Beetle, Ips sexdentatus (Coleoptera: Scolytidae), to Pheromone-Baited traps and Maritime Pine Logs

Non-host volatiles (NHV) were tested on antennae of Ips sexdentatus with coupled gas chromatographic-electroantennographic detection (GC-EAD). Significant antennal responses were found to aggregation pheromone components, ipsdienol and amitinol, an attraction inhibitor, verbenone, and non-host bark volatiles extracted from Betula pendula, including trans-conophthorin (tC) and alcohols. The tC, a blend of three green leaf alcohols (C6-alcohols), and a blend of two bark alcohols (C8-alcohols) were tested in combination for their ability to disrupt the attraction of the stenographer bark beetle to pheromone-baited traps, unbaited and pheromone-baited maritime pine logs. The strongest disruptive effect resulted from the addition of the tC combined with the blends of NHV alcohols at high release rate, achieving an 83% reduction in trap catches, 89% reduction of attacks on unbaited pine logs, and 60% on baited logs. It is proposed that the two types of NHV have an additive effect, tC playing a major role in pheromone disruption while the alcohols would interrupt host specific signals. The results suggest that I. sexdentatus uses both bark and green leaf volatiles from non-host tree species in the host selection process. These NHV are promising disruptants, which could be used to prevent stenographer bark beetle attacks on log piles or standing trees in forest. A mixture of conifers and broad-leaved species would also disturb olfactory guided host selection supporting the assumption that more diverse forests are less prone to pest insect outbreaks.

FIELD RESPONSE OF MARITIME PINE SCALE, MATSUCOCCUS FEYTAUDI DUC. (HOMOPTERA:MARGARODIDAE), TO SYNTHETIC SEX PHEROMONE STEREOISOMERS

The absolute configuration of the primary component of the maritime pine scale (Matsucoccus feytaudi) pheromone (i.e., (8E, 10E)-3,7,9-trimethyl-8,10-dodecadien-6-one) was determined as 3S,7R by field-trapping experiments using synthetic stereoisomers and according to previous NMR considerations. The 3R,7R isomer showed similar activity to 3S,7R, whereasM. feytaudi males responded very weakly to the two other candidates (3R,7S and 3S,7S). Further studies were conducted to optimize scale trapping for monitoring scale populations. Results of these studies showed that the trapping efficiency was related to pheromone dose, trap area, and wind speed but not to trap height.

Terpene Attractant Candidates of Dioryctria sylvestrella in Maritime Pine (Pinus pinaster) Oleoresin, Needles, Liber, and Headspace Samples

Capillary GC analysis was used to determine the proportion and quantity of terpenes in wood resin, pentane extracts from needles and liber, and headspace samples of needles and pruning wounds in 24 thirteen-year-old maritime pine. Fifteen different terpenes were identified in the samples. Germacrene D and β-pinene were the dominant terpenic compounds in the needles, while α-pinene and β-pinene were dominant in the liber and wood resin. Headspace samples of both needles and pruning wounds contained essentially monoterpenes. Only trace amounts of sesquiterpenes were found in pruning wound emissions. The presence of an oxygenated compound, linalool, in the pruning wound emissions is discussed, although this compound is not found in Maritime pine essential oil. Twelve of the 24 trees studied were infested by Dioryctria sylvestrella. Maritime pine susceptibility to this insect was related to the terpene composition of the different samples.

Honeydew feeding increased the longevity of two egg parasitoids of the pine processionary moth

The longevity of a generalist (Ooencyrtus pityocampae) and a specialist (Baryscapus servadeii) egg parasitoid of the pine processionary moth (Thau‐metopoea pityocampa) was compared under laboratory feeding conditions including water and honeydew from aphid species growing on maritime pine (Pinus pinaster) or pedunculate oak (Quercus robur).

Infestation dynamics of Dioryctria sylvestrella (Ratz.) (Lepidoptera: Pyralidae) in pruned maritime pine (Pinus pinaster Ait.)

Abstract The infestation dynamics of Dioryctria sylvestrella were studied for 2 consecutive years, in both pruned and unpruned maritime pine. In comparing four levels of pruning severity, the percentage of attacked trees and the location of attacks on the trunks were recorded. The level of attack of pruned trees strongly increased with the intensity of pruning, showing a significant positive correlation with the number of pruning wounds. The removal of dead branches did not result in any increase of infestation. The infestation of pruned trees had no contagious effect towards neighbouring unpruned trees. The location of attacks did not differ between either unpruned or any pruned tree treatments. The majority of the attacks were located in the vicinity of the branch insertion, and in 2-to 3-year-old internodes. In the second year, the percentage of pruned re-attacked trees continued to show a significant positive correlation with the severity of pruning. A model of infestation behaviour was hypothesised which involved two distinct phases. First, a primary attraction, mediated by components of oleoresin exuding from the pruning wounds, might allow the selection of an individual host tree. This attraction would be also quantitative and occur for at least 2 years. Second, female moths would select oviposition sites which would improve brood survival, providing easier access to suitable food resources.

Sensitivity of pruned maritime pine (Pinus pinaster Ait) to Dioryctria sylvestrella Ratz. (Lep., Pyralidae) in relation to tree vigour and date of pruning

Abstract: Infestation rate of Dioryctria sylvestrella was studied for the following three categories of maritime pine: (i) those trees that had been selected for pruning and pruned; (ii) those trees that had been selected for pruning but not pruned; and those trees that had neither been selected nor pruned. In comparing 10 diameter classes and 4 dates of pruning, the percentage of trees attacked was recorded. In both pruned and unpruned trees, the level of attack increased with tree diameter, according to a logistic curve. Pruned trees were significantly more infested than unpruned trees. Selection for pruning did not result in a significant higher rate of attack in unpruned trees. The percentage of pruned trees attacked did not differ significantly according to the date of pruning. The interaction between tree diameter and tree type did not induce any significant difference in infestation rate. The model of tree infestation, involving primary attraction for the female moth, was strengthened. Volatile attractants, originating in the constitutive oleoresin, might allow the selection of susceptible trees. Tree pruning, creating bark wounds, and tree vigour, increasing bark cracking, could similarly, though independently, increase constitutive resin flow, thus enhancing tree attractiveness.