© 2006 Plant Management Network.
Pink Hibiscus Mealybug Identification
Amanda Hodges, Entomology and Nematology Department, University of Florida, Gainesville 32611; and Greg Hodges, Division of Plant Industries, Florida Department of Agriculture and Consumer Services, Gainesville 32614
Hodges, A., and Hodges, G. 2006. Pink hibiscus mealybug identification. Online. Plant Health Progress doi:10.1094/PHP-2006-0414-01-DG.
Common Name: Pink Hibiscus Mealybug (PHM)
Primary Economic Host(s)
Tropical hibiscus (Hibiscus rosa-sinensis) is the most common host of the pink hibiscus mealybug. Other hosts of significance include Beautyleaf (Calophyllum spp.), Schefflera (Schefflera arboricola), Viburnum (Viburnum odoratissimum), and Florida nettle (Trema micranthum). Literature sources also indicate that cotton (Gossypium sp.), citrus (Citrus sp.), and several vegetable crops may be severely affected by infestation (3).
Scientific Name: Maconellicoccus hirsutus (Green)
Maconellicoccus hirsutus is classified in the mealybug or Pseudococcidae family and the order Hemiptera. More information on the taxonomy of M. hirsutus is available from Miller (7).
Although field identification is not sufficient for species confirmation of regulatory pests, it is an extremely useful tool for screening and tentatively identifying suspect mealybug samples. Slide mounting is necessary for a more definitive identification.
Several resources are available for field identification information (2,4,5,6,8). As males are rarely seen in the field and the immature or crawler stages of several mealybug species are difficult to differentiate from each other, identification focuses on the adult female. Some key features used in field identification include the following: lateral wax filaments (Fig. 1); shape and size; presence/absence of an ovisac; color of eggs (Fig. 2), and body color.
PHM has a reddish or pinkish body, one to two pairs of lateral filaments usually occurring at the posterior end of the body, and two ‘buttons’ of white wax on the abdomen (Fig. 3). Additionally, its body bleeds a reddish-brown fluid when pierced. When present, eggs are a bright pink to red color (Fig. 4). Field identification characteristics may not be as apparent in specimens preserved in alcohol for an extended period of time.
Signs of Damage
As with most mealybug species, high populations can result in excess production of honeydew, subsequently causing sooty mold growth. Also, since mealybugs feed on phloem tissue, heavy populations may cause wilting. Additionally, PHM injects a toxic saliva during feeding, which can cause a symptom known as bunchy top in hibiscus (10) (Fig. 5).
There are over 334 reported hosts of PHM, of which about 120 occur in Florida (3,4,8). Potential host species encompass at least 72 plant families and include numerous agriculturally important crops such as vegetables, legumes, grasses, rosaceous species, cotton, citrus, and ornamental plants. Infestation levels of PHM vary depending upon host availability and preference. In nurseries, H. rosa-sinensis appears to be a preferred host, while in natural areas, Florida nettle is preferred.
PHM is native to Asia, but has subsequently spread to Africa, Australia, Central America, South America, and North America (2,6). In the continental U.S., PHM was introduced into California in 1999 and Florida in 2002. PHM has been accidentally shipped to other states through the nursery trade, and its exact established distribution in uncertain.
Preparation of Slide Mounted Specimens
Slide-mounting is necessary to confirm species-level identification. Numerous references for preparing slides are available (1,8,9). If properly prepared, a slide-mounted mealybug specimen is indefinitely preserved.
Key Identification Characters
Identification of the mealybug is based on the morphology of its exoskeleton. Key characters in mealybug identification may include body shape, antennal segmentation, leg morphology, anal bar, ducts and pores, cerarii, and the circulus. It should be noted that all of these characteristics are not present in every mealybug species. Mealybug body shape may be oval (Fig. 6), elongate (Fig. 7), or round (Fig. 8). Antennal segmentation generally ranges from two to nine segments (Fig. 9), but species-specific and life-stage variation occurs. Immature stages will have few antennal segments than adults. Mealybugs with well-developed legs exhibit typical insect leg morphology with a coxa, trochanter, femur, tibia, tarsus, and tarsal claw (Fig. 10). Some species may have reduced or absent legs. Presence or absence of translucent pores on the coxa, trochanter, femur, tibia and tarsus is often a key character for identification. In particular, two pores present on the dorsum of each trochanter is a common feature in taxonomic keys. A presence of a denticle (tooth-like structure) on the tarsal claw is distinctive for some genera (Fig. 11). Small fine, translucent pores on the derm above the metathoracic leg may also be an important characteristic for identification (Fig. 12).
The anal bar, a sclerotized structure found within the anal lobe, may be strongly pronounced (Fig. 13), poorly pronounced or inconspicuous (Fig. 14), or lacking (Fig. 15).
Distribution and types of pores and ducts occurring on the ventral and dorsal derm are important in generic and species level identifications. The types of pores are bilocular, multilocular, quinquelocular, and trilocular. The trilocular pores (three locules or openings) are the most common pores found on the body and occur in most of the species. The trilocular pores are believed to produce the wax that covers the insect’s body. Quinquelocular pores (five locules) are most commonly associated with mealybugs in the genus Phenacoccus. The multilocular pores (six or more locules) are generally located around the vulva on the ventral abdominal segments. Multilocular pores produce the wax associated with the protection of the eggs.
The clusters of pores and setae arranged around the margin of the body are termed cerarii (Fig. 16). The lateral and posterior wax filaments that are commonly observed in the field are produced by these structures. A cluster or plate of trilocular pores with two short conical setae present in the center is a typical cerarri structure. The number of pairs of cerarri around the body can be an important taxonomic feature, and 17 pairs is the most common arrangement. Occasionally, filamentous or hair-like setae associated with the cerarii, known as ‘auxiliary setae’, are present (i.e., Pseudococcus and Dysmicoccus species).
The circulus, believed to assist in adhesion to plant material, is a simple area of variable size that lacks setae and pores. The shape and number of circuli is a useful character for distinguishing generic and species level identifications (Figs. 17, 18, 19, and 20).
The circulus may project from the body and is usually located between the fourth and fifth abdominal segments.
Key to Slide-Mounted Specimens of Common Scales Confused With Pink Hibiscus Mealybug in Florida
More specific information concerning M. hirsutus identification can be found in Miller 1999 (7). Also, the Pseudococcidae section of the ScaleNet database website (3) may provide additional resources and information on M. hirsutus and other mealybug species.
We would like to thank Dr. Douglass Miller, USDA ARS, for his editorial suggestions. This diagnostic guide was prepared from material developed for a Pink Hibiscus Mealybug workshop that was held in Gainesville, FL in June 2005. This workshop was made possible through a USDA-CSREES critical needs grant No. 2005-1763-02. Development of this critical needs grant was a collaborative effort involving the National Plant Diagnostic Network, the National IPM Center, USDA-CSREES, USDA-APHIS, and the National Plant Board.
5. Hodges, A. C., and Hodges, G. S. 2004. Standard operating procedures for plant diagnostic laboratories: Pink hibiscus mealybug, Maconellicoccus hirsutus (Green). Online. Nat. Plant Diagnost. Netw., hosted by So. Plant Diagnost. Netw., Univ. of Florida, IFAS.
6. Hoy, M. A., Hamon, A., and Nguyen, R. 2003. Pink hibiscus mealybug. Online. Featured Creatures No. EENY-29, Dept. of Entomol. and Nematol. of the Univ. of Florida-IFAS, and Div. of Plant Indust. of the FL Dept. of Agric. and Consum. Serv.
7. Miller, D. R. 1999. Identification of the pink hibiscus mealybug, Maconellicoccus hirsutus (Green) (Hemiptera: Sternorrhycha: Pseudococcidae). Insecta Mundi. 13:189-203.
9. Wilkey, R. F. 1962. A simplified technique for clearing, staining and permanently mounting small arthropods. Ann. Entomol. Soc. of Am. 55:606.
10. Williams, D. J. 1996. A brief account of the hibiscus mealybug Maconellicoccus hirsutus, a pest of agriculture and horticulture, with descriptions of two related species from Asia. Bull. Entomol. Res. 86:617-628.