L. M. McDonough

Insect sex pheromones : Effect of temperature on evaporation rates of acetates from rubber septa.

The half-lives (t1/2) for evaporative loss ofn-alkyl andn-alkenyl acetates from rubber septa were determined at temperatures varying from 15 to 35 °C. The changes int1/2 with temperature gave high correlations with the equation, Int1/2 = ΔH/RT+yo where ΔΔH is the heat of vaporization,R is the gas constant,T is the absolute temperature, andyo is a constant. Half-lives changed dramatically with temperature and the degree of change with temperature increased with increasing molecular weight. For mixtures, component ratios changed with temperature, but the degree was modest. At 20 °C there was a 7.5-fold ratio oft1/2 between members of the homologousn-alkyl orn-alkenyl acetates differing by two carbon atoms. The large change int1/2 with temperature and with number of carbon atoms is a consequence of the thermodynamic relationships and the temperature range of pheromone usage. Therefore, a similar degree of change inf1/2 with temperature and number of carbon atoms will apply to other formulations of the same type (those in which the rate of evaporation is first order). The values oft1/2 at 20 °C mainly agreed very well with those reported previously at room temperature. However, our previously reported values for pentadecyl and hexadecyl acetate were revised. Half-lives were shown to depend on the vapor pressure of a compound in the formulation substrate, but not on the vapor pressure of the pure compound.

Western avocado leafroller,Amorbia cuneana (Walsingham), (Lepidoptera: Tortricidae) : Discovery of populations utilizing different ratios of sex pheromone components.

The most effective lure for maleAmorbia cuneana (Walsingham) in Orange, Ventura, and Riverside counties of California was previously found to be a 1∶1 ratio of (E,E)-10,12- and (E,Z)-10,12-tetradecadien-1-ol acetates. In subsequent field tests in San Diego and Santa Barbara counties, this lure was ineffective. Analysis of sex pheromone glands (SPG) of femaleA. cuneana from these two counties showed theEE:EZ ratio to be about 1∶9 and synthetic lures of this composition were highly attractive in these areas. Analysis of the SPG of a number of females from both areas showed that there were three population types: two in the low ratio areas possessed 37 and 58%EZ, and the third in the high ratio areas possessed 89%EZ.

Sex Pheromone of the Codling Moth: Structure and Synthesis

The structure of a sex pheromone of the codling moth. Laspeyresia pomonella (L.), has been determined by spectrometric and chemical degradative techniques and by synthesis to be (2Z, 6E)-7-methyl-3-propyl-2,6-decadien-1-ol. In field cage tests the synthesized sex pheromone was as attractive as the natural, but neither was as attractive as ten virgin females per trap.

Response of male codling moths (Cydia pomonella) to components of conspecific female sex pheromone glands in flight tunnel tests

In flight tunnel tests, the percentages of oriented upwind flights of male codling moths culminating in contacting a source of different compositions of female sex pheromone gland components were determined over a dosage range of 0.1–100,000Μg. The following compositions were tested: (1) (E,E)-8,10-dodecadien-1-ol of 99.7% isomeric purity; (2) 1 + dodecanl-ol + tetradecan-1-ol; (3) 2 + decan-1-ol + (E)-9-dodecen-1-ol; and (4) an equilibrium mixture of 8,10-dodecadien-1-ol isomers (61%EE, 5%ZZ, 14%ZE, and 20%EZ). The ratios of the components in compositions 2 and 3 were chosen to produce vapor ratios equal to the natural ratios found in the female effluvium by Arn and coworkers. As the dose of composition 1 was increased from 0.1 to 10Μg, response increased from 0 to about 80% and then was approximately constant from 10 to 300Μg. Over the range 0.1–300Μg, the percentage of males contacting the septum was virtually the same as the percentage flying upwind. From 300 to 100,000Μg, the percentage of males flying upwind and contacting the source steadily decreased from about 80 to 0%. The male responses to compositions 2 and 3 were virtually identical to the response to 1. These results indicate, contrary to published reports, that dodecan-1-ol and tetradecan-1-ol in combination with 1 do not increase the responses of the behavioral modes determining degree of attractancy and disruption of sexual communication over that of 1 alone. These results also show that decan-1-ol and (E)-9-dodecen-1-ol do not enhance response in the five-component mixture. The response to composition 4 increased from 0% at a dose of 0.3Μg to 26% at a dose of 30Μg and then decreased to 0% at a dose of 3000Μg. Thus, the inhibiting effect of the isomers on response was greater at the higher doses.

Performance characteristics of a commercial controlled-release dispenser of sex pheromone for control of codling moth (Cydia pomonella) by mating disruption

Performance characteristics of polyethylene tube dispensers containing a mixture of (E,E)-8,10-dodecadien-1-ol (1), dodecan-1-ol (2), and tetradecan-1-ol (3) were evaluated for suitability as a mating disruptant for codling moth control. The rate of loss of pheromone component from a dispenser at any time was found to be described by the equation: −dP/dt=(k1k2 +kd)P whereP is the amount of pheromone component in the dispenser well;t is time;k1 is the ratio of the amount dissolved in the dispenser wall to the amount in the dispenser well;k1 is the ratio of the evaporation rate to the amount dissolved in the dispenser wall;kd is the rate constant for chemical decomposition. The evaporation rate,E, of a pheromone component at any time was given by:E=k1k2P For all three components during the first three weeks,k1 decreased from ca. 0.25 to ca. 0.10 and was approximately constant thereafter. The decrease ofk1 with time may have been caused by weather-induced cross-linking of the polyethylene. Over timek2 was constant and was 1.27 ± 0.26 × 10−3/hr for1, 1.96 ± 0.33 × 10su−3/hr for 2, and 0.31± 0.05 × 10−3/hr for 3. Thek2 was zero for2 and3 and 6.96 × 10−4 for1. After 150 days in an orchard in 1991, 95% of1 was lost from the dispensers (61% of the loss was by chemical decomposition and 39% by evaporation). The heat summation units in a Yakima valley orchard during 1991 were 4.7% above the average for the 1980–1991 period, while during 1990 they were the highest for this period (26% above average). After the first three weeks of dispenser aging, the regression line half-lives for1 for 1990 and 1991 were 31.0 and 35.1 days, respectively. The difference in temperature between 1990 and 1991 did not affect the half-life of1 very much because so much of the loss was from photochemically induced decomposition. Based on an estimate of the required minimum evaporation rate for mating disruption of 2 mg/ha-hr and a half-life of 35 days for1, 2345 dispensers/ha would be required for one application per season; 944 dispensers/ha for two applications per season; and 734 dispensers/ha for three applications per season. If a different emission rate of1 is required for reliable mating disruption, then the number of dispensers required would be changed proportionately.

EFFICACY OF NONPHEROMONE COMMUNICATION DISRUPTANTS OF CODLING MOTH (Cydia pomonella): EFFECT OF PHEROMONE ISOMERS AND OF DISTANCE BETWEEN CALLING FEMALES AND DISPENSERS

Field tests comparing the ability of codlemone, (E,E)-8,10-dodecadien-1-ol, and isomers of codlemone to disrupt pheromonal communication of codling moth were carried out. In a pear orchard, four nonisomerizing, gray septa dispensers were placed in the upper canopy of each tree containing a trap baited with 10 virgin female codling moths. The dispensers were at trap height and 70 cm from the edge of each trap. Trap catches of released male codling moths in three test areas were compared simultaneously when trees in each of the test areas contained unbaited dispensers, dispensers with 1 mg of codlemone containing 1% isomers, and dispensers with 1 mg of a test communication disruptant. When the test disruptant was an equilibrium mixture of codlemone and its isomers (61% codlemone, 39% isomers), the percent communication disruption was 86.8% compared to 68.7% for codlemone (P < 0.001). When the disruptant was (E,Z)-8,10-dodecadien-1-ol (94%EZ, 3%EE), the percentage disruption was 86.4% compared to 62.7% for codlemone (P < 0.002). These results show that the previously reported superior disruptant potency (relative to codlemone) of compositions containing codlemone with a high percentage of isomers was not a result of the proximity of the dispensers to the traps. The percent disruption of compositions of codlemone with 10 and 20% isomers was also determined. A plot of percentage disruption versus logarithm of percentage of nonpheromone isomers in the mixture from 1% to 97% gave a straight line withR2=0.93.

Codling moth (Cydia pomonella): Disruptants of sex pheromonal communication.

In a small section of an apple orchard, six traps were placed each in control and test areas and baited with live virgin female codling moths. Gray elastomer septa were used to dispense communication disruptants around the traps. Dyed male codling moths were released in control and test areas, and the numbers of males captured in control and test traps were compared. In 1991, linear regression curves of percent communication disruption versus logarithm of dose were obtained for three compositions: (E,E)-8,10-dodecadien-1-ol, codlemone (1); codlemone + dodecan-1-ol + tetradecan-1-ol (2); and an equilibrium mixture of the four isomers of 8,10-dodecadien-1-ol (30, (61%EE, 14%ZE, 20%EZ, and 5%ZZ). All three regressions gaver2 values greater than 0.90. At the 95% confidence limits, slopes and intercepts of compositions 1 and 2 were equivalent, and different from that of composition 3, which produced the greatest percentages of disruption at all doses. In 1992, five treatments were compared at a single dose: 1, 3, none (4), (Z,E)-8,10-dodecadien-1-ol (5), (E,Z)-8,10-dodecadien-1-ol (6). Compositions 5 and 6 gave the greatest and similar percentages of disruption and were different from codlemone (1) and 4 (95% confidence), but not from composition 3. Communication disruption produced by composition 3 was greater than (codlemone), which was greater than 4.

Sabulodes caberata Guenée (Lepidoptera: Geometridae) components of its sex pheromone gland

A 6,9-nonadecadiene, (Z)-9-nonadecene, andn-nonadecane were identified in extracts of sex pheromone glands of femaleSabulodes caberata Guenée. Potential pheromonal activity of gland components was assessed by electroantennogram measurements of gas-chromatographic fractions of abdominal tip extracts. Chemical identification was based on gas chromatography and mass spectrometry of parent compounds, hydrogenation products, ozonolysis products, dimethyl disulfide adducts, and synthesis. The monoene was synthesized via coupling of alkyl and acetylenic intermediates. (Z,Z)-6,9-Nonadecadiene (Z6,Z9-19∶H) was synthesized from methyl linoleate via chain lengthening. SyntheticZ6,Z9-19∶H had the same retention times on polar and nonpolar capillary gas-chromatographic columns as the 6,9-nonadecadiene from the sex pheromone glands. In field testsZ6,Z9-19:H alone produced trap catch of maleS. caberata and addition of (Z)-9-nonadecene orn-nonadecane had no effect on trap catch.

Sex pheromone of cranberry fruitworm,Acrobasis vaccinii riley (Lepidoptera: Pyralidae).

The following compounds and (approximate ratios) were identified in sex pheromone gland extracts of femaleAcrobasis vaccinii Riley by comparison of gas chromatography-mass spectrometric traces with those of synthetic standards: (E,Z)-, (Z,E)-, (Z,Z), and (E,E)-8, 10-pentadecadien-l-ol acetates (100:1:2:12), a dodecen-l-ol acetate (8), (Z)-8-, (Z)-9-, and (E)-9-pentadecen-l-ol acetates (3:23:4), two heptadecen-l-ol acetates (4:4), tetradecyl, pentadecyl, hexadecyl, and heptadecyl acetates (3:15:10:8), dodecan-l-ol (6), tetradecan-l-ol (5), and hexadecan-l-ol (23). The amount of (E,Z)-8, 10-pentadecadien-l-ol acetate (E8,Z10–15:Ac) in the extract was about 0.5 ng/female. Electroantennographic analysis of gas chromatographic fractions of female sex pheromone gland extract showed that the fraction containingE8,Z10–15:Ac elicited the greatest response. Alone,E8,Z10–15:Ac failed to elicit upwind flight of males in flight-tunnel tests, and traps baited with it did not catch males in field experiments. WhenE8,Z10–15:Ac was combined with (E)-9-pentadecen-l-ol acetate (100:4), male upwind flight response in flight-tunnel tests was equivalent to those obtained with extract of female sex pheromone glands (synthetic, 62%; natural, 51%), but the percent of males flying upwind that contacted the source was lower (synthetic, 47%; natural, 88%). The lower percent of source contact elicited by the synthetic pheromone could be a result of the difference in isomer ratios of 8,10–15:Ac in the natural and synthetic pheromone or could indicate that the synthetic pheromone is incomplete. Traps baited with the 100:4 combination caught large numbers of males in field experiments.

Sex attractant of the alfalfa looperAutographa californica and the celery looperAnagrapha falcifera (Lepidoptera: Noctuidae)

In field tests, traps baited with a combination of (Z)-7-dodecen-1-ol acetate (previously proposed to be the sex pheromone ofA. californica) and (Z)-7-dodecen-1-ol formate caught about 100 times as many males as (Z)-7-dodecen-1-ol acetate did alone. Highest catches of males were obtained with traps baited with 0.5 mg of (Z)-7-dodecen-1-ol acetate and 0.1 mg of (Z)-7-dodecen-1-ol formate impregnated on red rubber sleeve stoppers. The celery looper,Anagrapha falcifera, was also caught in traps baited with a combination of these two chemicals.