MATING DISRUPTION BY BLENDS OF SEX PHEROMONE AND ATTRACTION ANTAGONISTS

Peter WITZGALL
Swedish University of Agricultural Sciences, Box 44, S-23053 Alnarp, Sweden

The sex pheromone of pea moth, Cydia nigricana, is (E,E)-8,10-dodecadienyl acetate (E8,E10-12Ac); the geometric isomers E,Z-, Z,E-, and Z8,Z10-12Ac are strong attraction antagonists [1]. Each one of these four isomers is behaviourally active in a number of other Cydia species, either as main pheromone compound, attraction synergist or antagonist. Two closely related species use, for example, E,E/E,Z and E,Z/Z,E pheromone blends. respectively [2].

Pea moth males are attracted to fresh mating disruption dispensers releasing E8,E10-12Ac (98% isomeric purity; up to 31,µg/hr) in fields with up to 600 dispensers/ ha. After isomerization of E8,E10-12Ac to >6% of the antagonistic isomers, males are no longer attracted to the dispensers, but are instead observed to fly out of the treated pea fields [3.4].

Male pea moths respond to synthetic pheromone up to one hr before the onset of female calling. For mating disruption, it may be more effective to repel males by attractant/antagonist blends during the premating flight period, rather than to attract them.

In coaling moth, C. pomonella, all four isomers of d8,d10-12Ac are attraction antagonists [5]. The females produce the main compound codlemone, (E,E)-8,10-dodecadienol (E8,E10-120H), together with small amounts of the E,Z and Z,E isomers [6]. An equilibrium isomer blend of codlemone plus E,Z-, Z,E-, and Z8,Z10-120H is less attractive than pure codlemone [7], but more efficient for mating disruption [8].

The results of field tests on the behavioural role of E,Z-, ZE-, and Z8,Z10120H; and on mating disruption by codlemone, isomerized codlemone, and a blend of codlemone and codlemone acetate will be communicated.

The measurement of the dispersal and aerial concentrations of mating disruptant chemicals is fundamental to the optimization of dispenser load and placement, and the comparison of different experiments. A portable electroantennogram (EAG) apparatus, using the male antenna as sensor, allows direct detection of ambient pheromone [9]. In pea fields, field EAG measurements and gas chromatographic analysis of air samples are facilitated by a low background of volatile compounds [3,4]. Attempts are being made to measure aerial concentrations of codlemone in apple orchards.

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