Mealybug pheromones

As in the case of the Comstock and citrus mealybug pheromones, the release data for the California red scale pheomone showed that the laminate formulation made with 16-mil polymeric PVC film gave a long-lasting and suitable dispenser for the monitoring program. The results of these dispenser evaluations are summarized for citrus insect pheromones in Table IV. 

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). 

The sex pheromone component of the citrus mealybug. Pseudococcus cryptus Hempel (Homoptera Pseudococcidae), was identified as... 

Enantioselective syntheses of four different stereoisomers of the major component of the sex pheromone of the pink hibiscus mealybug, Maconellicoccus hirsutus, maconelliyl... 

It is rather difficult to convert carboxylic acids to decarboxylative alcohols. However, treatment of O-acyl esters (2) in the presence of Sb(SPh)3 and molecular oxygen, followed by hydrolysis, generates the corresponding decarboxylative alcohols. Eq. 8.11 shows the preparation of a sex pheromone of the citrus mealybug from (+ )-ds-pinonic acid [30-32]. When 1802 instead of 1602, is used in this reaction, 180-alcohols can be obtained. 

In 1980, we reported the structure of the Comstock mealybug, Pseudococcus comstocki (Kuwana), pheromone as 2,6-dimethyl-l,5-heptadien-3-ol acetate (24, 25) and in 1981, we identified the pheromone of the citrus mealybug, Planococcus citri (Risso), as (lR-cis)-(+)-2,2-dimethyl-3-(l-methylethenyl)cyclobutanemethanol acetate (26). Both of these pheromones have been synthesized and are currently being used as baits in monitor traps in California and Texas. These compounds are more volatile than the pheromones for most other insects and therefore formulations for controlled release need to be modified from those described earlier. 

The optically active citrus mealybug (CIMB) pheromone was intially formulated in laminate dispensers (13 x 13 mm) made of 9-mil vinyl and 16-mil polymeric PVG films. The dispensers, containing 1 mg of pheromone, were aged outdoors in California in late 1980 at temperatures ranging from 27-38°C in the day and 7-16°C overnight. Analysis for residual pheromone showed that over 98% of the lure was released by the vinyl dispensers in the first week (t /2 = 2 days), while the polymeric PVC formulations gave a slower release with a t, <2 of 11 days. 

A similar set of experiments was conducted for the development of a laminate dispenser for the Comstock mealybug (COMB) pheromone. Initially, 2-octyl acetate, which has a volatility and polarity similar to that of the pheromone, was used as a model and was incorporated in 3 types of laminate dispensers 16-mil polymeric PVC, 6-mil acrylic and 9-mil vinyl films were used. Dispensers (13 x 13 mm) containing 2.7 mg of compound were aged in a greenhouse in California at temperatures ranging from 21-36°C and then analyzed. The 2-octyl acetate contents gave two values of 1 day for the 9-mil vinyl, 8 days for the 16-mil polymeric PVC and greater than 40 days for the 6-mil acrylic film. On the basis of this experiment, the 9-mil vinyl and the 6-mil acrylic films were eliminated from consideration. 

A cyclobutanemethyl acetate, cfr-planococcyl acetate (297, R = CH2OAC), was claimed as a constituent of the citrus mealybug Planococcus citri, Risso) sex pheromone, and was prepared by photolysis of (+ )-cw-verbanone (298) followed by reduction and acetylation of the product 297 (R = CHO). The compound shown is the ( + )-(l/ )-cfr-isomer the trans- and (-)-isomers were... 

Further interest has been taken in the chemistry of scale insects and mealybugs. All four diastereoisomers of 3-methyl-6-isopropenyl-9-decen-l-yl acetate (59), a component of the pheromone of the California red scale insect, Aonidiella aurantii, have been prepared.(S)-(-)-Citronel1ol was epoxidised followed by copper-catalysed reaction with 3-butenylmagnesium chloride to yield (58) (Scheme 10). Following dehydration and removal of the component containing the tetra-substituted double-bond by epoxidation, (3S, 6 5)-(59) was obtained. Further separation into the active enantiomer (35,6fl) followed a h.p.l.c. procedure. 

Bierl-Leonhardt, B. A., Moreno, D. S., Schwarz, M., Fargerlund, J. and Plimmer, J. R. (1981) Isolation, identification, and synthesis of the sex pheromone of the citrus mealybug, Planococcus citri (Risso). Tetrahedron Leters, 22, 389-92. 

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. 

Our overall project goal was to identify and develop pheromones that could be exploited for the management of the four major mealybug pests in California vineyards. We report here the identification, synthesis, and results of field tests of the sex pheromone of the vine mealybug. Within the space of two years, the pheromone-baited traps have become the cornerstone of methods of monitoring this pest in California, and they are also being developed for sale and use in Sonih Africa, the Middle East, and South America. 

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. 

Lures diat had been loaded with 100-pg doses of the racemic pheromone and then field-aged for periods of 0-3 wk before deployment were equally attractive to male mealybugs (ANOVA, followed by Tukey s HSD tests Figure 4). Furthermore, the lack of differences persisted for 8 wk, from mid-August to mid-October adien the trial was halted due to autumn decline in mealybug populations. Over the course of this trial, >250,000 male mealybugs were caught in the pheromone-baited tr s. Thus, robber septa loaded with 100-pg doses of racemic pheromone may be effective lures for 12 i 4c or more. 

It is also interesting to note that for all nine of these mealybug and diaspidid scale species, the male insects are readily attracted to mixtures of the pheromone component(s) with other stereoisomers. This is in distinct contrast to the pheromone-mediated behavior of insects in other orders, such as moths and beetles, in which the males are frequently acutely sensitive to trace amounts of stereoisomers of the pheromone conq)onents, including both geometric isomers and enantiomers. The reason for this is that insects such as moths and beetles usually make use of a limited number of pheromone components, with species-... 

Scheme 2. Structures of known mealybug and diaspidid scale insect pheromone componentSo...

Second, male mealybugs and scales are acutely sensitive to their pheromones. For exanple, in the vine mealybug results presented here, pheromone lures loaded with 100 pg of racemic pheromone (i.e., SO pg of the... 

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