PROC. ENTOMOL. SOC. WASH. 95(1), L993, pp. 79-98 THE WHITE PEACH SCALE, PSEUDAULACASPIS PENTAGONA (TARGIONI-TOZZETTI) (HOMOPTERA: DIASPIDIDAE): LIFE HISTORY IN MARYLAND, HOST PLANTS, AND NATURAL ENEMIES LAWRENCE M. HANKS AND RoBERT F. DENNO (LMH) Post-doctoral Fellow, Department of Entomology, University of California, Riverside, California 92521; (RFD) Professor, Department ofEntomology, University of Maryland, College Park, Maryland 20742. Abstract.- The white peach scale, Pseudaulacaspis pentagona (Targioni Tozzetti), is a severe pest of woody ornamentals and fruit trees throughout the world. In this paper we review information on the life history, host plant relationships, and natural enemies of P. pentagona. Also, we present new data on the life history (fecundity and primary sex ratio), population biology (seasonal development, dispersal, dispersion and host plant range), and natural enemies (parasitoids, hyperparasitoids and predators) of P. pentagona. Key Words: Biological control, host plants, natural history, natural enemies, Pseudau- lacaspis pentagona (Targioni Tozzetti), white peach scale The white peach scale, Pseudaulacaspis bean and Pacific Islands, and the Americas pentagona (Targioni Tozzetti), is one of the where it feeds on a tremendous diversity of most damaging armored scale pests of host plants (Davidson et al. 1983). In the woody ornamentals and fruit trees in the United States, it occurs from Florida west world (Beardsley and Gonzalez 1975, to Texas and north to Maryland and Ten­ DeBach and Rosen 1976, Johnson and Lyon nessee (Davidson et al. 1983). 1988, Miller and Davidson 1990). By killing P. pentagona has long been confusedwith mulberry trees, P. pentagona threatened the its sibling congener, the white prunicola Italian silk industry (Howard 1916), and the scale, P. prunicola (Maskell). Both species widespread ornamental oleander was nearly are broadly sympatric, share many host plant eradicated from Bermuda (Simmonds 1958, species and occur abundantly throughout Bennett and Hughes 1959). P. pentagona Maryland and Virginia (Davidson et al. was first recorded in the United States in 1983, Rhoades et al. 1985). Despite the con­ Florida in the early 1900s (Gossard 1902) fusion of these two taxa in the early litera­ where it devastated the peach industry ture, they can be easily separated by taxo­ (Gossard 1902, Van Duyn 1967) and con­ nomic characters and also the color of their tinues to be a severe pest throughout the eggs (Davidson et al. 1983). Because eggs of southeastern United States (Johnson and P. pentagona are conspicuously white or Lyon 1988). coral in color, while those of P. prunicola P. pentagona is native to China (Gossard are pink, the species can be identifiedwhere 1902, Howard 1916, Murikami 1970), but this characteristic is reported (Davidson et is presently distributed throughout western al. 1983). Also, differences in host plant uti­ Europe, Asia, Australia, Africa, the Carib- lization exist between these two armored 80 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON Generation 3 - C'l E 2.00 () ' I 0+ I I 0+ I • 0 1.50 I z - � 1.00 +-' ·- (/) c I (1.) 0.50 I "C I I I I (1.) I - ro 0.00 () N D J F M A M J J A 5 0 N D J F M (j) Month Fig. 1. Average density ( + SE) of female P. pentagona (No.lcm2) on mulberry trees in the urban landscape of College Park, MD. Means are based on 20 samples (cuttings) taken from 5 field trees in April, July, September and November 1986, and March 1987. Samples taken during the first, second, and third scale generations were when most females were second instars (see Hanks 1991 for detailed methods). Bars at the top indicate the 3 annual generations. The occurrence of the crawler stage (unshaded bars) and the second instar + adult stage (shaded bars) are shown for each generation. scales. P. pentagona can be readily cultured to 5 discrete generations per year occur de­ on potatoes, while P. prunicola survives pending on the regional climate (Bennett poorly on this host (LMH unpublished data). and Brown 1958, Yonce and Jacklin 1974, In this paper we review information on Kozarzevskaja and Mihajlovic 1983, Da­ the life history, host plant relationships, and vidson et al. 1983). In Maryland, there are natural enemies of P. pentagona. We also three generations per year with highest den­ present new data on the life history (fecun­ sities of adults in August-October (Fig. 1). dity and primary sex ratio), population bi­ Successful overwintering takes place only as ology (season development, dispsersal, dis­ fertilized adult females (Bennett and Brown persion and host plant range), and natural 19 58, Kuitert 1967, Bobb et al. 1973, pers. enemies (parasitoids, hyperparasitoids and obs.). Some females deposit eggs prior to predators) of this important economic pest. the onset of winter, but these eggs usually fail to survive (Yonce and Jacklin 1974, Na­ 1990, LIFE HISTORY lepa and Meyer pers. obs.). Devel­ opment time from egg through adult ranges Seasonal development from 35 to 90 days (Bennett and Brown In the equatorial climate of Trinidad, P. 1958, Hughes 1960, VanDuyn 1967, Kui­ pentagona reproduces year round (Bennett tert 1967, Kozarzevskaja and Mihajlovic 1956), while at more temperate latitudes, 2 1983).Development time for the spring and VOLUME 95, NUMBER I 81 summer generations in Maryland is 60 and produce eggs, but can live as long as 60-7 5 50 days respectively and is inversely tem­ days (Bennett and Brown 1958, VanDuyn perature dependent (LMH unpublished and Murphey 1971, LMH unpublished data). data). We estimated the fecundity and primary Mating, Sex Detennination, sex ratio of P. pentagona from 110 infested Oviposition and Fecundity cuttings taken from 25 mulberry trees in Males begin searching for mates imme­ College Park, MD in February 1986 (see diately after emergence from the pupal case Hanks 1991 for detailed methods). Each (LMH pers. obs.). Males locate mates in re­ cutting was placed in a petri dish and ringed sponse to a pheromone emitted by females with Vaseline®, and all dishes were main­ (Heath et al. 1979, Einhorn et al. 1983). tained in an incubator at 26°C and 70% RH. Both sexes commonly mate with several in­ Average fecundity and sex ratio were esti­ dividuals and during mating the male stands mated at 76.7 and 0.96:1 (M:F) by counting on top of the female's cover (VanDuyn and and sexing (by color) the emerging crawlers Murphey 1971, pers. obs.). entrapped in the vaseline and dividing the Sex determination in P. pentagona as well count for each cutting by the number of as other armored scales is haplodiploid adult females/cutting. (Bennett and Brown 1958). The chromo­ Fecundity can be increased by raising P. some number for P. pentagona females (2N pentagona under warm temperature con­ = 16) and males (N = 8) is twice that of ditions (Yasuda 1983a) or on preferred host most other diaspidids suggesting a tetra­ plant species (Hughes 1960, Kozarzevskaja ploid origin (Brown and Bennett 1957, but and Mihajlovic 1983). Host plant condition see Nur 1990). In male eggs, paternal chro­ can also influence fecundity. For example, mosomes become condensed during mitotic we examined the effect of host plant water development and all functional chromo­ deficit on the fecundity and survivorship of somes are maternal in origin, while female P. pentagona by raising them on mulberry eggs contain functional chromosomes from trees subjected to low water and high water both parents (Bennett and Brown 1958). treatments (see Hanks 1991 for methods). Yeast-like symbionts are transmitted trans­ Fecundity was significantly lower on ovarially and may play a role in scale nu­ drought-stressed trees (26.4 + 4.8 eggs/fe­ trition (Brown and Bennett 1957, Miller and male) than on watered trees (36.5 + 2.3) Kosztarab 1979, Tremblay 1990). (ANOV A, F1•18 = 12.01, P = 0.003). Sim­ Adult females usually deposit eggs for pe­ ilarly, scale survivorship was significantly riods less than 10 days, but oviposition may lower on drought-stressed trees (69 + 8%) be extended in warmer climates (Kuitert compared to well-watered trees (84 + 4%) 1967, Yonce and Jacklin 1974). The eggs (ANOV A, Fus = 5.88, P = 0.02). and first instar crawlers of P. pentagona are While the primary sex ratio averages I: 1 both sexually dichronic and dimorphic in most populations (Brown and Bennett (Bennett and Brown 1958). First-deposited 1957, VanDuyn and Murphey 1971), it can eggs are female and are coral in color, which be altered by a variety of factors. Delayed are followed by white male eggs. Generally, fertilization of females may result in a strong the primary sex ratio is 1:1 (Brown and Ben­ male bias in the eggs (Brown and Bennett nett 1957, Van Duyn and Murphey 1971) 1957). A female-biased sex ratio results and average lifetime fecundity ranges from when scales are raised on fertilized host 50 to 200 eggs per female (Bennett and plants or under warm rearing conditions Brown 1958, Kuitert 1967, VanDuyn and (Yasuda 1983a, b). Murphey 1971, Bobb et al. 1973, Ball 1980, Some females of P. pentagona produce Yasuda 1983a). Unmated females do not only male eggs under certain conditions 82 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON ..= � • a. 1.00 0 s... a.. ....,= ,. 0.80 • • • 0+ •• • • • • 0+ 0.60 • • 0> c • ·- 0.40 • >. • (\3 • • • • _J 0.20 I • 0> i• 0> 0.00 w 0 1 2 3 4 5 6 7 2 Density (#22tcm ) Fig. 2. Relationship between the proportion of female P. pentagona laying only male eggs and the density of female scales on mulberry trees. Mulberry trees (34 2-year-old clones in the greenhouse) were artificially infested with scale eggs yielding a range of adult densities from 0.2 to 7.0 adult females/cm2).