Ezra DUNKELBLUM-a, Zvi MENDEL-a, Regine GRIES-b,
Gerhard GRIES-b
a-Institute of Plant Protection, Volcani Center, Bet Dagan 50250, Israel
b-Centre for Pest Management, Department of Biological Sciences, Simon Fraser University,
Bumaby, BC, Canada V5A 1S6
We have recently identified the sex pheromone of the Israeli pine best scale, Matsucoccus josephi as (2E,5R,6E,8E)-5,7-dimethyl-2,6,8-decatrien-4-one (MJP) [1,2]. This pheromone contains the same ketodiene moiety as the two other known Matsucoccus pheromones of M matsumurae, (2E,4E,6R,10R)-4,6,10-tetramethyl-2,4-tndecadien-7-one (MMP) [3,] and of M. faytaudi, (3S,7R,8E,10E)-3,7,9-trimethyl-8,10-dodecadien-6-one (MFP) [4] The configuration of the chiral center a to the ketone is R in all three Matsucoccus pheromones [2]. The three pheromones are different in one of the side chains (Fig.1). The three best scales, M josephi, M. faytaudi and M matsumurae are important pine pests and all three are geographically well separated.
The first field tests with racemic MJP and mixture of racemic E/ZMJP (containing equall amounts of 6E and 6Z isomers) indicated that the MJP is a kairomone of the predatory bug, Elatophilus hebraicus [5]. Further field tests, comparing the activity of MJP with the 5S antipode, the racemic pheromone and the 6Z isomers showed that the SR enantiomer (MJP) is the active pheromone of M. josephi males and kairomone of E. hebraicus [2,6]. The other stereoisomers are neither attradive nor inhibitory. Preliminary field results indicated that the M. feytaudi (MFP) and M. matsumurae (MMP) pheromones attract also E. hebraicus.
The use of a very sensitive GC-EAD system enabled the measurement of EAG responses from M. josephi male antennae [2] and E. hebraicus female antennae [6]. The strongest signal, from E. hebraicus, was obtained with MJP, but MFP and MMP evoked also significant responses.(Fig. 2) [6]. In order to evaluate the hypothesis that the EAG response is due to the ketodiene moiety of the Matsucoccus pheromones, two racemic analogs of MJP (ANLG 1 and ANLG 2) were tested by GC-EAD. Only the E-isomer of ANLG 1, containing a propyl group instead of the crotyl yroup in MJP, evoked a relative strong antennal response (Fig. 2) ANLG 2, containing a methacryl group, was inactive [6].
The level of attractancy in the forest of M. josephimales and of E. hebraicus adult males and females to MJP, MFP, MMP and analogs are presented in Table 1. The ratio of E. hebraicus males to females was between 3: 1 and 6: 1 [6].
The Matsucoccus josephi/Elatophilus hebraicus sex pheromone/kairomone system constitutes a special case of predator/prey relationship. This is the first record of an insect predator that exploits the sex pheromone of its prey as a kairomone. E. hebraicus responds strongly also to the sex pheromones of two allopatric Matsucoccus species, despite the fact that it is associated with M. josephionly. These findings suggest that the kairomonal activity of E. hebraicushas evolved during speciation of the genus Matsucoccus.