Aonidiella aurantii Scales

The California red scale, Aonidiella aurantii is a worldwide pest of citrus trees and the sex pheromone produced by the females has been identified as a mixture of the norsesquiterpenoid esters, 3-methyl-6-isopropenyl-9-decen-l-yl acetate (XV) and (Z)-3-methyl-6-isopropenyl-3,9-decadien-l-yl acetate (XVI)... 

Ethyl N-[2-(p-phenoxyphenoxy)ethyl]carbamate (Ro 13-5223, fenoxycarb, 56), a compound possessing high juvenile hormone activity, has gained practical importance in the control of various lepidopterous species, scale insects, fire ants and stored product pests (Fischer eta/., 1980 Masnere/a/., 1981 Dome/a/., 1981). It completely inhibits the population growth of the California red scale, Aonidiella aurantii in a concentration as low as 0.03%. It interrupts the development during morphogenesis and thus prevents eclosion of adults. 

Moreover, the effect of this compound was investigated not only for whitefly but also other insects. As an example, the experimental result for California red scale, Aonidiella aurantii, in an orchard is shown in Table 25.2.7 [34]. 

Table 25.2.7 Efficacy of pyriproxyfen on California red scale (Aonidiella aurantii) on apple trees.

Smith, J, M. 1957. Effects of the food plant of the California red scale Aonidiella aurantii (Mask.) on reproduction of its hymenopterous parasites. Can. Entomol. 89 219-230. 

Citrus oil components were evaluated for attractive or repellent activity toward the red scale, Aonidiella aurantii. Most hydrocarbon terpenes were attractive, while the alcohols, including linalool, were repellent. One aldehyde, citral, was attractive, while the other, citronellal, was repellent (21). 

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. 

The suitability of a host may be influenced by the host s food choice. Smith (1941) found that Habrolepis rouxi developed on the California red scale, Aonidiella aurantii, when the scale was reared on sago palm, but did not develop when the scale was reared on citrus. Campbell and Duffey (1979) reported that a-tomatine, an alkaloid in tomato plants, was toxic to Hyposoter exiguae developing in hosts fed the alkoloid. 

Host recognition by parasitic Hymenoptera also can be a complex process involving a series of behaviors after initial host contact that must be completed in sequence before an egg is laid. One such sequence is illustrated in Figure 5.7, which diagrams the processes by which Aphytis melinus, a parasitoid used for biological control of California red scale, Aonidiella aurantii, first identifies a potential scale insect species as a potentially suitable host, then assesses the individual quality of that host for utilization (Luck et al. 1982). Egg deposition is the final event of a chain of other behaviors that must be completed in sequence. The series can be broken in several placed and restarted, but no steps can be skipped. 

Females of the California red scale (Aonidiella aurantii) release a mixture of the branched unsaturated acetates (332a) and (333) to attract males. Synthesis of the R,Z component (332a) was achieved by Roelofs et al. 74, 75) starting from (5 -(+)-carvone (321) (Scheme 59). The final product consisted of a mixture of the Z and E isomers, which were easily separable by GC. The absolute stereochemistry of the 3-methyl group in (333) is unknown. 

The sex attractant of the female Japanese beetle, Popillia japonica, which attracts males, is (Z)-5-(l-decenyl)dihydro-2(3//)-furanone (73). The pure synthetic R,Z-isomer (144, Scheme 27) was competitive with females, and male response was strongly inhibited by small amounts of the 5,Z-isomer. The enantiomeric composition of the natural product has not been determined. The female also produces minor amounts of both the -isomer and the saturated analog but the roles of these compounds has not been established. Females of the California red scale, Aonidiella aurantii, emit a pheromone that attracts males (331). Two compounds have recently been identified and synthesized 3-methyl-6-isopropenyl-9-decen-l-yl acetate (332 a) and (Z)-3-methyl-6-isopropenyl-3,9-decadien-1-yl acetate (333, Scheme 50) (75). The four enantiomers of the latter compound were synthesized and only the R,Z-isomer proved to be attractive to male red scale. 

In contrast, in diaspidid scales such as Aonidiella citrina and A. aurantii, the female sex pheromone glands are found underneath the pygidium (Moreno, 1972 Moreno and Largerlund, 1975). In these scales, spherical glands appear on... 

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