Few attempts to control forest insects by means of pheromone mating disruption have been reported. The first such experiments with the European pine sawfly, Neodiprion sertifer (Hymenoptera: Diprionidae), resulted in nearly complete trap catch reduction, but no effects on population density or sex ratio were noted. Unmated females lay eggs, which develop into males only. Therefore, if mating disruption would be successful, a more male-biased sex ratio is expected the next generation. One possible explanation for the early results is that mated females disperse into the treated area, and thus obscure the effects of the treatment. In order to reduce the effect of such immigrating females, the treated area was increased in the experiment described here from the earlier used 0.5 – 4 ha to 25 ha. The acetate of erythro-3,7-dimethyl-2- pentadecanol was used for disruption and released from dispensers every 10 m. The influence on male orientation was monitored by pheromone traps, baited with the acetate of (2S,3S,7S)-3,7- dimethyl-2-pentadeanol and placed at 100 m interval along two perpendicular, 1500 m lines intersecting the treated area. The trap catch reduction was near 100% during the first month, but then declined to around 90% during the second month. Mating frequencies were checked by comparing the sex ratio of the next generation from within and outside the treatment area. No effect of the treatment on the sex ratio was detected, and the frequency of mated females could be assumed to be independent of treatment. Alternative hypotheses to explain the failure of pheromone mating disruption in N. sertifer are discussed

Anderbrant, Olle

Hedenström, Erik

Högberg, Hans-Erik

Lund University Publications

LUND UNIVERSITYPO Box 117221 00 Lund+46 46-222 00 00Pheromone mating disruption of the pine sawfly Neodiprion sertifer : is the size of thetreated area important?Anderbrant, Olle; Hedenström, Erik; Högberg, Hans-ErikPublished in:IOBC/WPRS Bulletin2002Link to publicationCitation for published version (APA):Anderbrant, O., Hedenström, E., & Högberg, H-E. (2002). Pheromone mating disruption of the pine sawflyNeodiprion sertifer : is the size of the treated area important? IOBC/WPRS Bulletin, 25(9), 111-116.http://phero.net/iobc/samos/bulletin/anderbrant.pdfTotal number of authors:3General rightsUnless other specific re-use rights are stated the following general rights apply:Copyright and moral rights for the publications made accessible in the public portal are retained by the authorsand/or other copyright owners and it is a condition of accessing publications that users recognise and abide by thelegal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private studyor research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portalRead more about Creative commons licenses: https://creativecommons.org/licenses/Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will removeaccess to the work immediately and investigate your claim.Use of pheromones and other semiochemicals in integrated productionIOBC wprs Bulletin Vol. 25(•) 2002pp. •-•Pheromone mating disruption of the pine sawfly Neodiprionsertifer: is the size of the treated area important?Olle Anderbrant, Erik Hedenström,1 Hans-Erik Högberg1Department of Ecology, Lund University, 223 62 Lund, Sweden - olle.anderbrant@ekol.lu.se1 Department of Chemistry and Process Technology, Mid Sweden University, 851 70 Sundsvall,SwedenAbstract: Few attempts to control forest insects by means of pheromone mating disruption havebeen reported. The first such experiments with the European pine sawfly, Neodiprion sertifer(Hymenoptera: Diprionidae), resulted in nearly complete trap catch reduction, but no effects onpopulation density or sex ratio were noted. Unmated females lay eggs, which develop into malesonly. Therefore, if mating disruption would be successful, a more male-biased sex ratio isexpected the next generation. One possible explanation for the early results is that mated femalesdisperse into the treated area, and thus obscure the effects of the treatment. In order to reduce theeffect of such immigrating females, the treated area was increased in the experiment describedhere from the earlier used 0.5 – 4 ha to 25 ha. The acetate of erythro-3,7-dimethyl-2-pentadecanol was used for disruption and released from dispensers every 10 m. The influence onmale orientation was monitored by pheromone traps, baited with the acetate of (2S,3S,7S)-3,7-dimethyl-2-pentadeanol and placed at 100 m interval along two perpendicular, 1500 m linesintersecting the treated area. The trap catch reduction was near 100% during the first month, butthen declined to around 90% during the second month. Mating frequencies were checked bycomparing the sex ratio of the next generation from within and outside the treatment area. Noeffect of the treatment on the sex ratio was detected, and the frequency of mated females could beassumed to be independent of treatment. Alternative hypotheses to explain the failure ofpheromone mating disruption in N. sertifer are discussed.Key words: Hymenoptera, Diprionidae, pest management, sex attractant, 3,7-dimethyl-2-pentadecanolIntroductionMany species within the sawfly family Diprionidae, pine or conifer sawflies, causesevere defoliation of pine (Pinus spp.) forests over large areas in Europe, Asia andNorth America (Smith 1993, Day & Leather 1997). Outbreaks are regularly controlledby aerial application of chemical insecticides such as Dimilin and various pyrethroids.Recently, attempts have been made to use the female produced sex pheromone forcontrolling populations of Neodiprion sertifer Geoffroy, one of the most widespread12 Anderbrant et al.and economically important diprionids. The method used has been mating disruption.In such experiments a relatively large amount of the pheromone is released in orderto obstruct the mate finding behaviour of the male. Unmated females lay eggs, whichdevelop into males only. Therefore, if mating disruption was successful, no drasticpopulation decline would be expected but instead a more male-biased sex ratiowould occur in the next generation.In the first mating disruption experiments with N. sertifer a near complete trapcatch reduction was obtained in small (0.5 ha) plots. However, due to a generalcollapse of the population in the area, no evaluation of sex ratio or density could bedone of the next generation (Anderbrant et al. 1995a). In the following experimentsthe treated areas were increased to around 4.5 ha. Also in this case a dramatic declinein trap catch was recorded, but no apparent effects on sex ratio, larval density ordefoliation could be detected (Anderbrant et al. 1995b). These two studies used theattractive pheromone isomer, the acetate of (2S,3S,7S)-3,7-dimethyl-2-pentadecanol,either alone or in its erythro-blend, as disruption agent. In a third study, theantagonistic (2S,3R,7R)-isomer  was used, either alone or in combination with theattractive isomer, but this failed to improve the mating disruption (Anderbrant et al.1998).One hypothesis that could explain these negative results is that, due to the highpopulation density during such epidemic conditions that prevailed during theseexperiments, males are still able to locate females. However, observations of femaleseither inside or outside a treated area clearly showed that only a small fraction ofthose inside mated compared with those outside (Östrand et al. 1999). An alternativehypothesis is that mated females disperse into the treated area, and thus obscure theeffects of the treatment. In order to reduce the effect of such immigrating females, thetreated area was increased in the experiment described here from earlier 0.5 – 4 ha to25 ha. The success of the pheromone treatment was monitored by traps within andoutside the treated area and by collection of next generation larval colonies for acheck of the sex ratio.Materials and methodsThe study was performed in a Scots pine, Pinus sylvestris L., plantation nearValdmarsvik in the province of Östergötland, southeast Sweden, during 1993. Thetreated area consisted of several stands mainly with young pines, 2 – 5 m in height.Some stands with older trees or mixed with Norway spruce, Picea abies Karst., werealso included.The mating disruption dispenser consisted of a dental cotton roll (Celluron No.2, Paul Hartmann, S.A., France) impregnated with 8 mg of the acetate of erythro-3,7-dimethyl-2-pentadecanol (Hedenström & Högberg 1994). The dispensers were hungin trees at about 2 m height under a sun- and rain-protection made from wax-Mating disruption of the pine sawfly 3impregnated cardboard. Dispensers were placed 10 m apart in a square grid 500 by500 m on the 27 July to 1 August. Based on measurements in the laboratory and field(Anderbrant et al. 1992), the release of the active (2S,3S,7S)-isomer was estimated atabout 180 mg ha-1 for the whole season (60 d).The ability of the males to find an odour source was monitored by Lund-I stickytraps (Anderbrant et al. 1989) placed 100 m apart along two perpendicular linesintersecting each other at the centre of the treated area. Eight traps were inside thetreated area, four were at the border and 20 traps were outside. The traps wereplaced in pines about 2 m above the ground and were loaded with 100 µg of theacetate of the attractive (2S,3S,7S)-isomer, synthesised according to Högberg et al.(1990). Sticky bottoms were replaced on 23 August and 7 September, and baits wererenewed on 7 September. The trapping was finished on 6 October.Larval density within the plantation was recorded in spring before theexperiment. Two trees every 50 m along two lines were inspected and the number ofcolonies counted. However, because nearly all of these trees were located within anarea, which later was chosen for treatment, a complementary census of the defoliationwas performed. This was made according to the method described in Anderbrant etal. (1995b), using four trees every 100 m along half the length of each transect, fromthe centre to the outer end. In total 40 trees outside and 20 inside the treatment wereinspected.The sex ratio of the generation following the mating disruption treatment wasestimated by collection of larval colonies, which were reared until cocoon formation.Rearing took place in ventilated cardboard boxes and larvae were moistened dailyand fed fresh pine twigs when needed. Twentyfour colonies were collected fromeach of the areas inside and outside the treatment. This was done in June 1994 andthe colonies were reared individually. In addition, approximately 15 colonies werecollected from each of five sites inside the treated area and four sites outside it, alongone of the transects. All colonies collected from one individual site were rearedtogether until cocoon formation. The cocoons were sex determined based on size,females being about twice as large as males.Results and discussionSimilar to the results from previous studies, the pheromone treatment caused a nearlycomplete trap shut down (Figure 1): Average trap catches of male N. sertifer for thewhole season were 612 ± 298 (SD, n=20), 180 ± 161 (n= 4) and 38 ± 47 (n=7, onetrap had fallen down and was excluded from the analysis) for traps outside, at theborder and inside the treated area, respectively. The catches, transformed tolog(catch+1), inside and outside were significantly different (P=0.002, t-test, unequalvariances). The trap catch reduction was complete during the first three weeks, butduring the last month of trapping it was only just over 90 % (Figure 2).4 Anderbrant et al.020040060080010001200750 650 550 450 350 250 150 50 50 150 250 350 450 550 650 750Distance from centre of treatment (m)TreatmentTreatment020040060080010001200Figure 1. Total catch in pheromone traps along the two perpendicular tansects through themating disruption treatment.August 1-23051015202530outside border insideAug. 23 - Sept. 7020406080100120outside border insideSept. 7 - Oct. 6050100150200250300350400450500outside border insideAverage trap catchFigure 2. Catch in pheromone traps positioned along the transects outside, inside or at the borderof the mating disruption treated area during different periods since start of the experiment.Mating disruption of the pine sawfly 5On the average 7.4 larval colonies per tree (n=48) were recorded in the plantationbefore the treatment. Considering that most trees were small (mean 2.4 m in height)this represents a high population level and some of the trees were completelydefoliated. This was confirmed by the defoliation census performed in the autumn:The proportion of inspected shoots that was consumed by the larvae inside thetreated area was 0.37 ± 0.36 (n=20) compared with 0.73 ± 0.32 (n=34, six treeswere omitted from the analysis as their height made the inspection unreliable) outsideit. Although this difference was statistically significant, P<0.05 (t-test of arcsinesquare-root transformed proportions), the population densities before the applicationof mating disruption were at the same high level inside and outside the treated area.The survival rate was rather low of the larvae collected for determination of sexratios from the generation following the disruption experiment. In many of theindividually reared colonies less than 10 individuals survived to cocoon formation(Figure 3). However, it was quite obvious that in all of the colonies, with a reasonablenumber of survivors, both sexes were represented. The average sex ratio (proportionof males) was not significantly different outside, 0.49 ± 0.28 (n=24) compared toinside 0.46 ± 0.30 (n=24) of the treatment. The results from the rearing of groups ofcolonies were similar (Figure 3), with a mean sex ratio of 0.52 ± 0.16 (n=4) outsideand 0.56 ± 0.05 (n=5) inside the treated area.Single colonies11010010001 10 100 1000Males + 1Multiple colonies11010010001 10 100 1000Males + 1Females + 1Females + 1Figure 3. Number of male and female cocoons in colonies collected inside (filled) oroutside the mating disruption treated area. Colonies were reared either singly orseveral together.The results obtained in this experiment confirm those from earlier attempts to disturbthe mating in N. sertifer (Anderbrant et al. 1995a, b, 1998); it is possible to reduce the6 Anderbrant et al.catches to very low levels without affecting the proportion of mated females insidethe treatment, as measured by the sex ratio of colonies. However, it has also beenclearly shown that females inside pheromone treated areas are only rarely able toattract males (Östrand et al. 1999). Instead the females seem to disperse if they havenot been able to attract males during the first days in the area. These contradictingresults may be explained by a massive immigration of mated females into the treatedarea. Because no female attractants are known, this hypothesis is difficult to test. Analternative hypothesis is that even if the movement of females was higher inside thanoutside the pheromone treatment (Östrand et al. 1999), the females sooner or latermated while still inside the treatment. A test of this hypothesis requires tracking thefemales inside a pine plantation, and a suitable technique for doing this will certainlybe difficult to develop.The pheromone dose used in this experiment is about 100 times lower thanwhat is normally used in many lepidopteran mating disruption experiments (e.g.Leonhardt et al. 1996). Although the trap shut down and the reduction in matingfrequency seemed to be nearly complete in the N. sertifer experiments, there is still apossibility that the final result would be different if higher pheromone doses wereused. One could also hypothesise that the ”restlessness” in females is not only aresponse to the lack of courting males, but also to the pheromone per se. Aprerequisite for this is that females can perceive their own pheromone. Although thisis the case for a few lepidopteran species (see e.g. Ljungberg et al. 1993), it is as yetunknown if it occurs among pine sawflies. It should also be observed that theexperiments were done under epidemic conditions, while most suceessful disruptionattempts involving moths have occurred when the population densities have beenrelatively low.In conclusion, our results indicate that the size of the treated area, up to 25 ha, isof little importance for the success of mating disruption in N. sertifer.  Possibleimprovements include use of higher dose and, maybe more important, treatment ofless dense populations. Also treatment of isolated stands, where immigration isnegligible, would possibly generate results that are easier to interpret.AcknowledgementsWe thank Fredrik Östrand, Rolf Wedding and Erling Jirle for their excellent help withthe fieldwork. Funding was provided by Carl Trygger Foundation, C. F. LundströmsStiftelse, Stiftelsen Futura and the Swedish Council for Forestry and AgriculturalResearch (SJFR).Mating disruption of the pine sawfly 7ReferencesAnderbrant, O., Löfqvist, J., Jönsson, J. & Marling, E. 1989: Effects of pheromone trap type,position and colour on the catch of the pine sawfly Neodiprion sertifer (Geoffr.) (Hym.,Diprionidae). Journal of Applied Entomology 107: 365-369.Anderbrant, O., Bengtsson, M., Löfqvist, J. & Baeckström, P. 1992: Field response of the pinesawfly Neodiprion sertifer to controlled release of diprionyl acetate, diprionyl propionate andtrans-perillenal. Journal of Chemical Ecology 18: 1707-1725.Anderbrant, O., Löfqvist, J., Hedenström, E. & Högberg, H. -E. 1995a: Development of matingdisruption for control of pine sawfly populations. Entomologia Experimentalis et Applicata74:83-90.Anderbrant, O., Löfqvist, J., Hedenström, E. & Högberg, H. -E. 1995b. Mating disruption of thepine sawfly Neodiprion sertifer (Hymenoptera: Diprionidae): effects on pheromone trap catch,sawfly sex ratio and density and on tree damage. In: Behavior, Population Dynamics, andControl of Forest Insects, Proceedings of the International Union of Forestry ResearchOrganizations Joint conference, February 1994, eds. Hain, Salom, Ravlin, Payne and Raffa:415-427.Anderbrant, O., Högberg, H. -E., Hedenström, E. & Löfqvist, J. 1998. Towards the use of pinesawfly pheromones in forest protection: Evaluation of behavioral antagonist for matingdisruption of Neodiprion sertifer. In: Proceedings: Populations Dynamics, Impacts, andIntegrated Management of Forest Defoliating Insects. U.S. Department of Agriculture, ForestService, Northeastern Forest Experiment Station. Gen. Tech. Rep. NE-247, eds. McManus andLiebhold: 53-63.Day, K. R. & S. R. Leather, 1997. Threats to forestry by insect pests in Europe. In: Forests andInsects, Chapman and Hall, London, eds. Watt, Stork and Hunter: 177-205.Hedenström, E. & Högberg, H. -E. 1994: Efficient opening of trans-2,3-epoxybutane by a higherorder cuprate: Synthesis of erythro-3,7-deimethylpentadecan-2-yl  acetate, pheromone ofpine sawflies. Tetrahedron 50: 5225-5232.Högberg, H. -E., Hedenström, E., Wassgren, A. -B., Hjalmarsson, M., Bergström, G., Löfqvist, J. &Norin, T. 1990: Synthesis and gas chromatographic separation of the eight stereoisomers ofdiprionol and their acetates, components of the sex pheromone of pine sawflies. Tetrahedron46: 3007-3018.Leonhardt, B. A., Mastro, V. C., Leonard, D. S., McMane, W., Reardon, R. C. & Thorpe, K. W.1996: Control of low-density gypsy moth (Lepidoptera: Lymantriidae) populations bymating disruption with pheromone. Journal of Chemical Ecology 22: 1255-1272.Ljungberg, H., Anderson, P. & Hansson, B. S. 1993: Physiology and morphology of pheromone-specific sensilla on the antennae of male and female Spodoptera littoralis (Lepidoptera:Noctuidae). Journal of Insect Physiology 39: 253-260.Östrand, F., Wedding, R., Jirle, E. & Anderbrant, O. 1999: Effect of mating disruption onreproductive behavior in the European pine sawfly, Neodiprion sertifer (Hymenoptera:Diprionidae). Journal of Insect Behavior 12: 233-243.Sanders, C. J. 1996: Mechanisms of mating disruption in moths. In: Insect Pheromone Research:New Directions, Chapman & Hall, New York, eds. Minks and Cardé: 333-346.Smith, D. R. 1993: Systematics, life history, and distribution of sawflies. In: Sawfly LifeHistoryAdaptations to Woody Plants, Academic press, New York, eds. Wagner and Raffa: 3-32.

Pheromone mating disruption of the pine sawfly Neodiprion sertifer : is the size of the treated area important?

Abstract

Similar works

Full text

Available Versions

Lund University Publications