Chemical Senses Vol.17 no.5 pp.543-553, 1992

A portable EAG system for the measurement of pheromoneconcentrations in the field

Ame E.Sauer, Gerhard Karg, Uwe T.Koch, Jacobus J.De Kramer1 andRoland Milli2

Universit&t Kaiserslautem, Fachbereich Biologie, 6750 Kaiserslautern,1 Landwirtschaftliche Versuchsanstalt der BASF A. G., 6703 Umburgerhof and2Biologische Bundesanstalt filr Land-und Forstwirtschaft, 6915 Dossenheim,Germany

Abstract. A robust and portable apparatus for the measurement of pheromone concentrations under fieldconditions has been developed. It uses the insect antenna (Lobesia bolrana Hb.) itself as a sensitive andspecific pheromone detector. Shock-proof contact with the electrodes is maintained by fixing the antennain a specially-shaped plexiglass holder mounted within a glass tube. This allows measurements to be madewhile moving the apparatus. Continuous airflow through the tube is generated by a suction pump and theincoming air can be purified by passage through a charcoal filter. This allows to readjust the offset and tocalibrate the instrument by the application of pheromone pulses of known concentrations. Removal of thefilter allows the direct access of ambient air over the antenna which responds by generating an electro-antennogram (EAG) as a measure of the pheromone concentration.

Using the calibration curve, relative pheromone concentrations in ambient air in a vineyard can be determined.Sample measurements from areas treated with artificial pheromone for pest control are presented

Introduction

In recent years, there has been considerable progress in the application of pheromonesfor insect pest control. One successful method is to treat the area to be protected withartificial sex pheromone which leads to a strong reduction in the rate of reproductionof the insects. This 'mating disruption' method has been applied successfully inmonocultures (Roelofs, 1975; Ridgway et al., 1988) for example in vineyards for thecontrol of the grape vine moth (Eupoecilia ambiguella and Lobesia botrana) (Am, 1979;Charmillot et al., 1985; Englert, 1985; Neumann etal., 1985; Vogtand Schropp, 1985).

While the effectiveness and the commercial applicability of this method have beenwell demonstrated, it is still an open question, which parts of the reproductive behaviourare actually affected by the pheromone application. Apart from the necessary investiga-tion, and analysis of behaviour and its modifications, it seems useful to determine thepheromone concentration, and the modes of pheromone distribution and propagationin the biotope during pheromone application.

Experiments to simulate the propagation of odour plumes were carried out by Murlisand Jones using a point source of ions (Murlis and Jones, 1981). Their results, however,may not fully describe the situation of a pheromone treated vineyard, since theinteractions of ions with vegetation (adsorption, desorption) might be quite differentfrom the surface interactions of pheromones. In addition, there is usually a large numberof pheromone sources in a mating disruption application which may lead to differentplume structures.

In order to measure pheromone concentrations directly, gas chromatographs or massspectrometers could be used. The highest sensitivity and flexibility, however, can be

© Oxford University Press 543

at Russian A

rchive on Decem

ber 26, 2013http://chem

se.oxfordjournals.org/D

ownloaded from

A.E.Sauer el at.

expected when the antenna of the insect itself is used as detector. Baker and Haynes(1989) and our group (Sauer, 1989; Milli and de Kramer, 1989; Sauer and Koch, 1989;Karg et al., 1990) have developed methods for recording electroantennograms in thefield permitting to gain information about the pheromone distribution in the field. Inthis paper, we present a method capable of quantitative measurements of pheromoneconcentrations in the field using the electroantennogram method.

Materials and methods

Animals

The experiments were performed with antennae from Lobesia botrana, reared in theLandwirtschaftliche Versuchsanstalt of BASF, Limburgerhof. The male pupae werekept separately at 21 °C until eclosion, and then stored at 9°C in a refrigerator. Onlyantennae from males aged 2—4 days were used.

Pheromones

For calibration purposes, we used the main component of the pheromone of Lobesiabotrana, (E,Z)-7,9-dodecadienylacetate (Buser et al., 1974), synthesized by BASF.Different concentrations of 10~2 to 1CT7 were obtained by dissolving the pheromonein paraffin-oil (Merck No. 7161). In this context, a concentration of e.g. 10~2 meansthat 0.01 ml of pheromone were dissolved in 0.99 ml of paraffin-oil. Betweenexperiments, the different pheromone solutions were kept in a freezer at — 18°C. Thepheromone sources in the field were standard pheromone dispensers produced by BASF.They consist of small plastic containers filled with the main component of the Lobesiapheromone. The dispensers had been set up in an experimental vineyard at a densityof approximately 500 dispensers/ha. In the following the vineyards treated withpheromone dispensers will be named treated vineyards and the vineyards treated withcommon insecticide will be named untreated vineyards.

Experimental apparatus

Antenna holder. Devices for recording antennograms as published in the literature havebeen difficult to use under field conditions, since they used glass capillaries, manipulatorsand preparation methods requiring handling precision and long preparation times. Thus,we intended to develop a system of rugged design without the need for complicatedhandling equipment. The antenna holder is machined from a plexiglass disc of 3 mmthickness and a diameter of 20 mm (Figure 1). It contains two wells (r = 3.5 mm,h = 1.5 mm) having a distance of 2 mm. These wells contain the recording electrodes(Ag-AgCl, 1.5* 1 mm diameter; ZAK Miinchen E201 M). Between the wells a slit,1.2 mm wide, is cut into the disc leaving thin walls between the slit and the wells.A groove about 100 /xm wide and 1 mm deep is cut into each wall, forming an outletfrom the well into the slit. The antenna is cut from the moth's head using microscissors.It is then placed into the grooves, bridging the slit and making connections to the twowells. A hole 100 /tm diameter has been drilled inside each wall, parallel to the slitjust beneath the surface of the disc. Through these holes, small insect pins are pushed.They cross the grooves above the antenna and thus lock the antenna in place, such thatit cannot be lifted out of the grooves by capillary forces or by shock. The wells are

544

at Russian A

rchive on Decem

ber 26, 2013http://chem

se.oxfordjournals.org/D

ownloaded from

A portable EAG system

Fig. 1. Perspective schematic drawing of the plexiglas antenna holder, w = Well; s = slit, g = groove;e = electrodes, h = hole; c = cables.

pCZB—o

1cm

Fig. 2. Schematic drawing of the antennogram recording system. The antenna holder (4) is placed insidea glass chamber (3a,3b). The outlet of the glass chamber is connected to a suction pump (5) generating aconstant airflow over the antenna. The pheromone in the ambient air can be removed by a charcoal filter(1). Calibration signals are generated by a motor driven syringe (2). In order to measure the pheromoneconcentration in the ambient air, one simply removes the charcoal filter.

then filled with saline (Kaissling and Thorson, 1980). To improve contact, the endsof the antenna protruding into the wells are freshly cut under saline using microscissors.This antenna holder provides stable contact between antenna ends and saline and permitsfast and reproducible antenna preparations.

545

at Russian A

rchive on Decem

ber 26, 2013http://chem

se.oxfordjournals.org/D

ownloaded from

A.E.Sauer el al.

Measuring chamber. In standard antennogram preparations, the stimulating air mixturesare usually blown over the antenna using compressed air jets. In a device measuringpheromone concentrations in the ambient air, this method would require the air to beblown over the antenna by a device similar to a ventilator. In such a set-up, thepheromone could be absorbed by the ventilator blades, and the flow of the surroundingair could be influenced by the ventilator airstream. In our system, the air is movedtowards the antenna by suction. To this end, the antenna holder is placed inside ameasurement chamber (Figure 2), consisting of two glass tubes (3a, 3b) joined by aflange at the site of the antenna holder (4). The glass tubes isolate the antenna holderfrom the ambient air. A continuous stream of air is generated by a membrane suctionpump (5) placed at the outlet end of the measurement chamber. This 'main air current'is monitored by a cone flow meter and amounts to 42 ml/s. The main air current velocityis 50 cm/s. This corresponds to an average wind velocity in field. In order to measurethe antenna's resting potential in clean air, a charcoal filter (1) can be attached to theinput of the measurement chamber, removing pheromone components from the inflowingair. When the charcoal filter is removed, the EAG elicited by the ambient air can berecorded. The cross-section of the charcoal filter was 70 cm2 and presented nomeasurable resistance to the airflow. It was checked that the attachment and removalof the filter in clean air did not alter the antenna's potential.

Calibration. Since the EAG amplitudes of individual antennae generated by the samepheromone concentration are quite variable and since the sensitivity of the antennaeshows degradation, it is necessary to provide calibration signals at frequent intervals.For this purpose, a short puff of air with known pheromone content can be added tothe main air current while the charcoal filter is put on the measuring chamber inlet.The calibration air puffs are generated by a metal-glass syringe (20 ml, Aesculap, Isocal)mounted on a mechanical drive with a stepper motor. The syringe contains a 1 ml glassvessel filled with the pheromone-paraffin-oil solution. The vapour pressure of theparaffin-oil and the pheromone generate a defined mixture of air, paraffin-oil vapourand pheromone vapour with a constant composition, regardless of the actual syringevolume (Kafka, 1970). When the syringe drive is activated, a volume of 0.75 ml ofthis mixture is added to the main airstream within 0.2 s, which generates a well definedcalibration response of the EAG.

Antennogram recording system. The electronic amplifier consists of a high impedanceinput stage (amplification X10) mounted closely to the measuring chamber, and a mainamplifier, built as a plug-in unit. The total amplification is 100-fold. The main amplifiercontains a continuously adjustable low pass filter (12 db/octave), a DC offset circuitand a system for measuring the impedance of the antenna. Standard FET inputoperational amplifiers are used throughout, providing easy maintenance and repair. Theantennograms are recorded directly on a portable chart recorder (Gould 220). Theyare also stored on a tape recorder (Uher 4200 Report Stereo) via an FM-modulator.The measuring system (measuring chamber, calibrator, pump, electronics, and taperecorder) is mounted in a small portable rack permitting convenient transportation. Thewhole measuring system is operated with the standard 220 V 50 Hz line supply. Forfield measurements, a small gasoline-powered AC generator is used (Honda EX 650).

546

at Russian A

rchive on Decem

ber 26, 2013http://chem

se.oxfordjournals.org/D

ownloaded from

A portable EAG system

a)

coBbroUon putm

1s

1mV

10~7 1CT6 10-5 1 0 -4 1 0 -3

b) c

UfltUMftt da

untreatedvtrxyurd

pherecnoo* traoUdvbwyard

FTg. 3. (a) EAG responses to pheromone calibration pulses of different intensity. The numbers indicate theconcentration (ml/ml) of pheromone [(E,Z)-7,9-dodecadicnylacetate] in paraffin oil as kept inside the synnge(cf 2 in Fig. 2). (b) EAG response in a vineyard without artificial pheromone application (conventional pestmanagement with insecticides). We assume that the small EAG response is caused by other odourants likeplant volatiles. (c) EAG response from ambient air in a vineyard with standard pheromone application (500dispensers/ha) for pest control.

-*—I

10-7 \o-' io"s 10-4 io-J io~2

PHEROUONE CONCENTRATION [RELATIVE UNITS]

Fig. 4. Standardized calibration curve. The dose — response curves of 25 antennae were normalized to theresponse at a stimulus of 10~4 and then averaged. The error bars indicate the standard deviation.

This solution has the advantage that the system can be run both in the laboratory andin the field without any change. There is no need for special battery-operated equipment.

547

at Russian A

rchive on Decem

ber 26, 2013http://chem

se.oxfordjournals.org/D

ownloaded from

A.E.Sauer et al.

Results

Calibration of the EAG

The antennogram responses to the pulses from calibration syringes containing differentpheromone concentrations are shown in Figure 3. For pheromone concentrations between10~7 and 10~5, the responses have a rise time of 50 ms, and a time constant of thedecay of 200 ms. For larger pheromone concentrations, we observed a further increasein the time constant of decay up to approximately 300 ms at a concentration of 10~4.

The responses to calibration pulses of a concentration of 10~3 are much prolonged,indicating a slower recovery of the system. However, this concentration value is onlyused on rare occasions. The amplitude variance of successive pulses of identicalconcentrations is in the order of 3% for concentrations of 10~4 and below, providedthat a pause of 5 s between stimuli is maintained. At a concentration of 10~5, the pausebetween stimuli can be as short as 2 s.

On a longer time scale, one observes a steady degradation of the antennae's response,such that an antenna can only be used over a period of 30 min. This slow degradationmakes it necessary to repeat the calibration in intervals of, e.g. 3 min. One would assumethat it should be necessary to reconstruct the whole calibration curve every time. Wefound, however, that the antenna's degradation affects all points of the calibration curvein the same manner, i.e. if the response to the syringe with 10"4 pheromone concentra-tion is reduced by, e.g. 20%, then the responses for the 10~5 and 10~6 are alsoreduced by 20%. Thus, for the frequent recalibrations, it is sufficient to measure thesensitivity of an antenna at one representative calibration point, e.g. using a syringewith 10~4 pheromone concentration. Since this measurement is quite fast, therecalibration does not noticeably reduce the total measuring time. Thus, the antennacan be used for quantitative measurements over the whole period of 30 min.

Calibration curves measured for a large number of antennae over a long period oftime showed that all antennae had a rather stereotyped calibration curve form. Whenall calibration curves were normalized on the response amplitude generated by a syringecontaining a concentration of 10~4, the curves resembled each other very closely.

Figure 4 shows an averaged normalized calibration curve taken from 25 antennae.Thus, using the normalized calibration curve, one can combine normalized responsesof different antennae and get consistent measurement results.

Field measurements

Figure 3 shows a set of recordings taken in an experimental vineyard (Billigheim, Pfalz,Germany). Five calibration pulses are shown together with ambient air measurementsin an area where pheromone dispensers were present (treated vineyard) and in a controlarea, where only neurotoxic insecticides had been used (untreated vineyard).

For evaluation, the EAG amplitudes generated by the ambient air (Figure 3b,c) weredivided by the amplitude generated by the reference calibration pulse of 10"4

concentration. This normalized amplitude is transferred to the normalized calibrationcurve (Figure 4), and converted to a pheromone concentration value (in relative units).

Table I shows the results of measurements in a treated and an untreated area. Thesevalues were measured with different antennae. The table shows a relatively smallstandard deviation of the normalized EAG amplitudes. When converted to concentra-

548

at Russian A

rchive on Decem

ber 26, 2013http://chem

se.oxfordjournals.org/D

ownloaded from

A portable EAG system

Table I. A set of measurements taken in a continuous series (total duration: 1 Vi hours) in two vineyardsat Wachenheim. The individual measurement points show the relatively small variability of the values.AV: average; MED: median; SD: standard deviation; R50. range of 50% of values; RAN: total range of values.

(a) Untreated vineyard

Ambient air (A)EAG [mV]

1.21.10.70.70 91.01.10.6

(b) Treated vineyard

Ambient air (A)EAG [mV]

5.14 95.64.23 64.33.33.32.75.3

Reference (B)EAG [mV]

5.34.63.83.24.23.84.02.4

Reference (B)EAG [mV]

5 55.25.44.33.84.53.33.62.95.6

Relative (A/B)

AV:SD:

RAN:

0.230 240.190.220.210.260.280 23

0 230.028

0.19-0 28

Relative (A/B)

AV:SD:

RAN:

0.930.951.040.970.950.961.000.920.920.94

0.950.029

0.92-1.04

Concentration[relative units]

MED:R50

RAN.

2.0*2.3*1.2*1.7*1.5*3 0*3.9*2.0*

2.0*2.0*

-3 .0*1.2*

- 3 . 9 *

Concentration[relative units]

MED:R50:

RAN:

6.3*7.2*1.6*8.2*7.2*7.7*1.0*5.9*5.9*6.7*

7.2*6.3*

- 8 . 2 *5.9*

-1 .6*

10"7

lO"7

10"7

10"7

lO"7

10"7

10"7

lO"7

lO"7

io-7

io-7

10"7

lO"7

lO"5

10"5

io-4

lO"5

lO"5

10"5

lO"4

io-5

io-5

io-5

10"5

10"5

io-5

io-5

io-4

tion values, these small variations are enlarged due to the logarithmic shape of thecalibration curve. It must be mentioned that at least some part of the variability resultsfrom small fluctuations of the pheromone density in the ambient air. This is also indicatedin the time course of the sample shown in Figure 3c.

The antennogram responses in the control area correspond to a pheromone concentra-tion of approximately 500 times lower than in the areas treated with artificial pheromone.We assume that these background responses are due to odourants emitted by the plants.Preliminary measurements have shown that the antennae of Lobesia botrana respond

549

at Russian A

rchive on Decem

ber 26, 2013http://chem

se.oxfordjournals.org/D

ownloaded from

A.E.Sauer el al.

IBFBKBNCB(B) AMBIENT A H (A)

l_T\r\laVl

U EXXBIOn) 2 B 4m

b)

k i i rDISTANCE TO THE VINEYARD [m]

10

Fig. 5. Decline of the pheromone concentration with increasing distance from the edge of a pheromone treatedvineyard, (a) EAG responses measured in different distances to the vineyard. The first curve shows the responseto a reference stimulus of 10~4. (b) Normalized responses to three different measurement series. The relativepheromone concentrations in a distance up to 6 m reach a level comparable with the pheromone level foundin untreated areas.

to substances like Geraniol or Linalool which are known to be present in a vineyard(G.Karg and A.E.Sauer, unpublished results).

Since the contribution to the overall signal is rather small, the background signalcan be neglected if relative concentrations in different parts of the same pheromonetreated area are to be measured. Measurements in untreated vineyards have shown,that the background signals are the same within one vineyard. This indicates that thereare no unevenly distributed odourants that influence the EG-Amplitude. Consideringthe responses to the background, an EAG response of 25 % of the maximum responseseems a large signal which should not be neglected. However, this argument does nottake into account the logarithmic relationship between EAG response and pheromonedensity. The correct evaluation of this dose-response curve gives the result that therelative concentration of background signals is only 0.2% of the maximum pheromoneconcentration.

Especially with respect to the pheromone application for mating disruption it isimportant to gain information about the pheromone concentrations in and around thetreated area. Within the boundaries of the treated vineyard the pheromone concentra-tion is rather constant (relative value of 0.92 —1.04, see Table Ib). It seems that the

550

at Russian A

rchive on Decem

ber 26, 2013http://chem

se.oxfordjournals.org/D

ownloaded from

A portable EAG system

pheromone is homogenously distributed.Figure 5 shows the pheromone concentrations in different distances from a treated

area. At a distance of 4 - 6 m from the edge of a vineyard the decline of the averageEAG amplitude corresponds to a decline in the pheromone concentration of a factorof 10 (see Figure 3 Calibration Curve). This decline of the pheromone concentrationis very drastic.

Discussion

The pheromone concentrations existing in fields that were treated with pheromone formating disruption can be estimated very roughly by considering the dispenser spacing,the release rates measured by dispenser weight loss and assumptions on the averagedwell time of a pheromone molecule in the air volume of the treated area. These con-siderations yield concentration values of 0.01 to 1 ng/m3. Concentrations can also bemeasured by gaschromatographic methods if one absorbs the pheromone in a cartridge,which is later washed out with a small volume of solvent which is then injected intoa gaschromatograph (Chang et al., 1989). While these methods seem useful for absoluteconcentration measurements, it requires long sampling times (up to several hours) and,thus, can only yield concentration values averaged over these sampling periods. Direct'online' recording of varying pheromone concentrations could in principle be done bya mass spectrometer directly and continuously analyzing the ambient air. However,the sensitivity limit of such a directly operating mass spectrometer is on the order of1 part per billion, which is several orders of magnitude above the estimated pheromonelevels. Thus, the use of the insect's antenna as a sensor for the detection of a specificpheromone seems an adequate solution to this measurement problem.

The set-up used by Baker and Haynes (1989) has shown the feasability of pheromonedetection in the field with high sensitivity. However, Baker and Haynes' apparatus cannotbe used to measure pheromone concentrations as encountered in a field treated for matingdisruption. In their set-up, the antenna is continuously exposed to the ambient air. Thus,it is not possible to observe the antenna's resting potential since it cannot be shieldedfrom the ambient air which is always containing pheromone. Also, calibration pulses,as used by Baker and Haynes would superimpose on the ambient air signal and thismakes the evaluation of calibration signals ambiguous.

In our system, the antenna is kept in a controlled atmosphere, which can either beclean air (as filtered by the charcoal filter), or clean air plus calibration pulse or ambientair (as sucked over the antenna when the charcoal filter is removed.) Our system,therefore, permits correct calibration as well as the continuous measurement ofpheromone concentrations and fluctuations of the concentration level. At present, theopening of the calibrating syringe is always in contact with the main airstream. Thisimplies the possibility that small amounts of the calibration mixture may diffuse intothe airstream and generate small constant pheromone background. We are currentlydeveloping a device to avoid this diffusion effect, which should further improve theprecision of the apparatus.

Our results show, that reliable measurements of pheromone concentrations in treatedfields are possible. The results may be used to relate field concentrations to concentra-tions found to be effective in laboratory experiments and thus help in the investigationof the mechanisms responsible for mating disruption. The results may also lead to fur-

551

at Russian A

rchive on Decem

ber 26, 2013http://chem

se.oxfordjournals.org/D

ownloaded from

A.E.Sauer el al.

ther improvement in mating disruption techniques. At present, our system supportspractical field optimation experiments, since the observed concentrations can becompared with pest control efficacy. The observed time resolution is sufficiently fastto permit recordings of fluctuations in the pheromone concentrations in the field.

Now we have a tool to investigate the structure of pheromone clouds, such asfluctuations, which are considered to be of great importance in mate finding oflepidopterans (Baker et al., 1985). These measurements are still in progress and willbe published at a later time.

Our first results with the presented device have shown that the decline of thepheromone concentration at the edge of a pheromone treated area has consequencesfor the application. In order to prevent mating of the pest insect close to the area tobe protected and to prevent the inflight of fertilized females into this area, the applicationhas to exceed the boundaries of the treated area.

The system can also be used in a laboratory set-up to test pheromone blends or plantvolatiles. The air stream generated by suction, and the charcoal filter, make the systemindependent of the composition of the ambient air in a laboratory. Thus, contamina-tions in the laboratory air resulting from previous pheromone experiments or other odoursources cannot influence the EAG responses recorded in our set-up.

Acknowledgements

We gratefully acknowledge the help of BASF AG, Ludwigshafen, who supplied thepheromones and experimental animals and some financial support. Thanks are due toHelmut RothhaB, who let us use his vineyard to make some of our experiments. G.Kargwas supported by the GraduiertenfSrderungsprogramm of Rheinland-Pfalz. We wouldlike to express special thanks to Prof. Ulrich Bassler who generously supported thisproject and took a constant interest in its progress.

References

Arn.H. (1979) Developing insect control by disruption of sex pheromone communication: Conclusions fromprograms on lepidopterous pests in Switzerland. In: Ritter.F.J. (Ed.), Chemical Ecology: OdourCommunication in Animals. Elsevier, North-Holland, pp. 365-374.

Baker.T.C. and Haynes.K.F. (1989) Held and laboratory electroantennographic measurements of pheromoneplume structure correlated with oriental fruit moth behaviour. Physiol. Entomol., 14, 1-12.

Baker.T.C., Willis,M.A., Haynes.K.F. and Phelan.P.L. (1985) A pulsed cloud of sex pheromones elicitsupwind flight in male moths. Physiol. Entomol., 10, 257-265.

Buser,H-R., Rauscher.S. and Arn.H. (1974) Sex pheromone of Lobesia botrana: (E,Z)-7,9-dodecadienylacetate in the female grape vine moth. Z Naturfoschung, 29c, 781-783.

Chang.J.F., Benedict,.!.H., Payne.T.L., Camp.B.J. and Vinson.S.B. (1989) Collection of pheromone fromatmosphere surrounding boll weevils, Anthonomus grandis. J. Chem. EcoL, 15, 767—777.

Charmillot.P.J., Bloesch.B., Schmid.A. and Neumann,U. (1985) Essais de lulte contre Cochylis Eupoeciliyambiguella HBNpar la technique de confusion sexueUe. Application en agronomic, Valence, 1985, Ed.INRA, Paris, 1988, 176-188.

Englert.W.D. (1985) Freilandversuche mit dem synthetischen Pheromon Z-9-DDA zur Verwirrung derMannchen des einbindigen Traubenwicklers Eupoecilia ambiguella. Gesunde PJlanzen, 37, 461-471.

Kafka.W.A. (1970) Molelailarc Wechselwirkungen bei der Erregung einzelner Riechzellen. Z vergl. Physiol.,70, 105-143.

Kaissling,K.-E. and Thorson,J. (1980) Insect olfactory sensilla: Structural, chemical and electrical aspectsof the functional organization. In Saitelle.D.B., Hall.LM. and Hildebrand.J.G. (Eds), Receptor forNeurotransmitters, Hormones and pheromones in Insects. Elsevier/North Holland, Biomedical Press,Amsterdam, New York, Oxford, pp. 261-282.

552

at Russian A

rchive on Decem

ber 26, 2013http://chem

se.oxfordjournals.org/D

ownloaded from

A portable HAG system

Karg,G., Sauer.A E. and Koch,U.T. (1990) The influence of plants on the development of pheromoneatmospheres measured by EAG method. In: Elsrtcr.N. and Roth.G. (Eds), Brain-Perception-Cognition.Proceedings of the 18th Gdttingen Neurobiology Conference. Thieme Verlag Stuttgart, New York, p. 301.

Milli.R. and de KramerJ.J . (1989) An EAG Detector for field pheromone measurements. In Eisner,R.and Singer.W. (Eds), Dynamics and Plasticity in Neuronal System. Proceedings of the 17th GottingenNeurobiology Conference. Thieme Verlag, Stuttgart, New York, p. 77.

Murlis,J. and Jones,CD. (1981) Fine scale structure of odour plumes in relation to insect orientation todistant pheromone and other attractant sources. Physiol. Entomol., 6, 71—86.

Neumann,U., Vogt,H., Schropp,A., Englert.W.D. and Schruft.G. (1985) Lutte par la confusion sexuellecontre la Tordeuse de la grappe (Cochylis) Application en agronomie, Valence, 1985, Ed. INRA, Paris,1988, 167-174.

Ridgway.R., SUverstein.R.M. and Inscoe,M. (Eds) (1988) Practical Applications oj Insect Pheromones andOther Anractants. Marcel Dekker Inc, New York.

Roelofs.W. (1975) Manipulating sex pheromones for insect suppression. Environ. Lett., 8, 41—59.Sauer.A.E. (1989) Ein System zur Mcssung von Pheromonkonzentrationen lm Freiland mit Elektro-

antennogrammen Diplomarbeit, Universitat Kaiserslautern.Sauer.A.E. and Koch.U.T. (1989) Are filter papers reliable stimulating devices in insect olfactory investiga-

tions? In: Elsner,R. and Singer.W. (Eds), Dynamics and Plasticity in Neuronal System. Proceedings ofthe 17th G6ttingen Neurobiology Conference. Thieme Verlag, Stuttgart, New York, p. 78.

Vogt,H. and Schropp.A. (1985) Freilandversuche zur Bekampfung des einbindigen Traubenwickkrs (Eupoedliaambiguella Hbn.) mit Hilfe der Konfusionsmethode. Gesunde Pflanze, 37, 431-439

Received on January 18, 1992; accepted on July 13, 1992

553

at Russian A

rchive on Decem

ber 26, 2013http://chem

se.oxfordjournals.org/D

ownloaded from