Volatiles released from oak, a host tree for the bark beetle Scolytus intricatus.

Volatile compounds emitted in different phases of oak (Quercus robur) development (bark, unopened buds, young developing leaves, and blossoms) were analyzed with the aim of finding possible host-plant attractants for the European oak bark beetle, Scolytus intricatus. Complex mixtures of aliphatic, aromatic, and terpenoid compounds were identified in the samples. (E)-2-Hexenal and hexanal dominated in samples of bark. In buds, (Z)-3-hexenyl acetate formed a substantial part of the mixture. In both leaves and blossoms (E,E)-alpha-farnesene was the main component.Volatiles released from oak twigs and branches during both the maturation feeding and construction of maternal galleries by Scolytus intricatus were also analyzed. Most compounds found in the samples from females' and males' maturation feeding were identical. High contents of anisole, (E)-beta-ocimene, alpha-copaene, one unidentified sesquiterpenic hydrocarbon C(15)H(24) and beta-caryophyllene were found in both samples of twigs attacked by beetles. During the construction of maternal galleries by bark beetles in oak logs, monoterpene hydrocarbons such as p-cymene, (E)-beta-ocimene, and gamma-terpinene, and sesquiterpenes alpha-copaene and beta-caryophyllene were released in large quantities. No new compound appeared when males were added to the log with feeding females.

Mirasorvone: a masked 20-ketopregnane from the defensive secretion of a diving beetle (Thermonectus marmoratus).

The sunburst diving beetle, Thermonectus marmoratus, ejects a milky fluid from its prothoracic defensive glands when disturbed. Two major volatile components of this secretion are steroids; cybisterone (structure 7) constitutes about 20% of the volatiles, and a new steroid, mirasorvone, about 50%. Mirasorvone is assigned an 18-oxygenated pregnane structure (structure 9) on the basis of extensive spectroscopic data. Although no 18-oxygenated steroid has been described previously from an insect source, a closely related hormone with mineralocorticoid activity, 18-hydroxydeoxycorticosterone (structure 13), has been isolated from the adrenal glands of rats.

New mimics of the acetate function in pheromone-based attraction.

Several analogues of (Z)-8-dodecenyl acetate (1a), the major pheromone component of the Oriental fruit moth, Cydia molesta, with chloroformate and lactone functional groups in place of the acetate moiety, were synthesized and investigated for their biological activity at four evaluation levels, i.e. by electroantennography (EAG), electrosensillography (ESG), short-range sexual stimulation and activation in the flight-tunnel. We found very strict requirements on the shape as well as on the electron distribution of the acetate group for a productive interaction with the receptor. The behavioral results showed that, among the analogues investigated, the chloroformate 1b, alken-4-olide 2a and also dodecyl acetate (1c) possess significant (60-85%) inhibitory activities. Based on electrophysiological evidence demonstrating that (i) only 1b is competing with the major pheromone component 1a for the same receptor sites on the male antennal sensilla, (ii) 1c elicits moderate EAG but no ESG responses and (iii) 2a does not produce any electrophysiological response at all, three possible inhibitory mechanisms by which these analogues are acting could be distinguished.

Propheromones derived from codlemone.

Tricarbonyl [(8,9,10,11-η-8,10-dodecadien-l-ol] iron and the corresponding acetate prepared from 8,10-dodecadien-1-ol or its acetate, comprise the protected double-bond system of the molecule. After coming in contact with ambient oxygen, the iron complexes in question slowly release the corresponding pheromones of, for example, the codling moth,Cydia pomonella, and the pea moth,Cydia nigricana in highE,E purity and amounts that are sufficient for pest monitoring. A simple dispenser for propheromone application is proposed. Results of release rates in laboratory conditions and field trials are given.

Structure-activity correlations among analogs of the currant clearwing moth pheromone.

Eleven analogs of (E,Z)-2,13-octadecadien-1-yl acetate1, a main pheromone component of the currant clearwing moth,Synanthedon tipuliformis Clerk (Lepidoptera: Sesiidae) were synthesized and tested for their biological activities by electroantennography (EAG). To correct the EAG data for differences in volatility of the analogs, their vapor pressures were estimated by a gas chromatographic method. All structural changes in the parent molecule were found to reduce the biological activity to various degrees. The most active analog tested was the carbamate12, whose activity was almost comparable to that of the pheromone component1. Structure-activity correlations showed that hydrophobic, steric, and electronic effects of chain terminal groups might be responsible for variations in biological activity of the conformationally unchanged (E,Z)-2,13-analogs.

Male confusion of the nun moth with disparlure at high and low population densities.

The feasibility of using the synthetic sex pheromone, disparlure, as a mating confusant of the nun moth (Lymantria monacha L.) was investigated on wild populations occurring in outbreak proportions in Poland and in low density in Czechoslovakia. The size of experimental plots ranged from 1 to 12 hectares. The amounts of pheromone applied were 10 or 20 g/hectare. Three types of slow-release formulations of a racemic mixture of disparlure were tested: (1) a spray formulation with latex as a carrier, (2) a tubing of natural rubber, and (3) sawdust of a porous material used for making tips of fiber-tip pens. All three pheromone formulations prevented significant numbers (98.6-100% in the low density situation, 90-96.2% during the outbreak) of the males from locating a discrete source of pheromone (a trap containing synthetic pheromone or a female) during the whole flight period, indicating long-lasting efficiency of the formulations.

Rubber substrates and their influence on isomerization of conjugated dienes in pheromone dispensers.

Release rate and degree of isomerization of pheromones with conjugated double bonds were studied in dispensers prepared from several rubber substrates. The substrates compared were made of rubber, cured with elemental sulfur or accelerators based on organic sulfur compounds or organic peroxides. Isomerization of the double bonds occurs immediately after impregnation of the substrate, and the degree of isomerization increases during field use and/or storage. The propensity of the isomers to isomerize corresponds to their proportion in the equilibrium mixture. AnE,Z isomer is isomerized faster than theE,E isomer, and finally a near-equilibrium mixture of the four isomers is present. Minimal isomerization was found in non-sulfur-cured substrates which are the material of choice.

Methylbutynol effectively replaces methylbutenol, a pheromone component ofIps typographus (L.) (Coleoptera: Scolytidae).

In field experiments in Sweden, the constituent 2-methyl-3-buten-2-ol of the aggregation pheromone of the spruce bark bettleIps typographus (L.) was effectively replaced by 2-methyl-3-butyn-2-ol.