Lavandulyl senecioate

Two pheromonal components were detected in airborne collections from the vine mealybug, Planococcus ficus Signoret (Hemiptera Pseudococci dae) in Israel. They were identified as (5 )-lavandulyl senecioate (1) and (5)-lavandulyl isovalerate (II). Compound I has been identified as the sex pheromone of P. ficus in California. The report shows that feral P. ficus mealybugs produce and respond only to (I) whereas mealybugs reared in the laboratory on potato sprouts produce and respond to both (I) and (II). 

Abstract— The sex pheromone of the vine mealybug Planococcus ficus has been identified as a single component, (5)-lavandulyl senecioate 2a. Males were equally attracted to either (S)-2a or racemic 2a, indicating that the unnatural enantiomer does not inhibit male behavioral responses. 

Racemic lavandulol was prepared by hydrolysis of lavandulyl acetate (TCI America, Portland, OR) in 1 M NaOH in 95% ethanol. Racemic lavandulyl senecioate was synthesized by esterification of lavandulol as described above. 

Blend Ratios. Blends of 0, 1,3.3,10,33, or 100 pg of racemic lavandulol with 100 pg of racemic lavandulyl senecioate were tested from 2 to 23 May 2001, with traps and lures replaced on 16 May. In this and subsequent trials, data was transformed [(x + 0.5) ] and analyzed by one-way ANOVA, followed by a means separation test (Student-Newman-Keuls test, a = 0.05). 

Dose. Having determined that lavandulyl senecioate was the sole conq)onent of the attractant, doses of 0, 10,33,100,333, and 1000 pg of racemic lavandulyl senecioate (6 replicates) were tested from 13 June to 7 July 2001, with traps and lures replaced on 21 June. 

Comparison of Racemic and Chiral Pheromone. Lures, replicated 6 times, were loaded with either 25 pg of (5)-(+)-lavandulyl senecioate, or 50 pg of the racemic material. Traps were set out on 21 September and collected on 28 September 2001. Trap counts were compared with a two-sample /-test. 

Figure L GC chromatogram of volatiles collected from mature female vine mealybug on butternut squash (top) and from uninfested squash (bottom, inverted), Lavandulol 1 and lavandulyl senecioate 2a are indicated.

Having verified the stereoisomeric purity of alcohol 1, a portion was converted to the chiral pheromone, (5)-(+)-lavandulyl senecioate 2a (78% yield), by treatment wiA senecioyl chloride and pyridine in ether 16). 

Because lavandulyl senecioate is chiral, and vine mealybug females produce exclusively die (iS)-enantiomer, the relative attractiveness of pure (5)- and racemic lavandulyl senecioates was tested. Traps baited with either die chiral or racemic pheromone were equally attractive to male mealybugs (racemic, 373 175 [mean SD] (5)-enantiomer, 286 122 two-sample /-test, P = 0.34), clearly demonstrating that die unnatural enantiomer is neidier inhibitory nor synergistic. 

Figure 3. Numbers of male vine mealybugs caught in traps baited with blends of racemic lavandulol and lavandulyl senecioate ranging from 0 100 to 100 100 pg. Note Y-axis is a log scale. Bars surmounted by different letters are significantly different.

Figure 4. Male vine mealybugs caught in traps baited with racemic lavandulyl senecioate, with lures aged for periods of 0 to 3 wk before use. They-axis is a log scale. Controls were lures treated with solvent only. For a given sampling date, there were no differences between treatments, but all treatments were always different from the solvent controls.

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