Phenacoccus defectus Ferris



Common name

Imperfect mealybug

Field characters

Occurring on foliage, crown, and roots of host.

Validation characters

Multilocular pores restricted to venter of segments VII and VIII, rarely on VI; without quinquelocular pores; cerarii with primarily 2 conical setae; circulus oval, divided or usually undivided by intersegmental line; oral-collar tubular ducts restricted to venter of abdomen; dorsal setae conical; antennae 7-, 8- or 9-segmented; denticle on claw.


Phenacoccus defectus is similar to P. solani Ferris and P. solenopsis Tinsley by lacking dorsal multilocular pores, dorsal oral collars, and quinquelocular pores. It is possible that P. defectus is a variant of one of these species. Phenacoccus defectus can be distinguished by having multilocular pores restricted to segments VI or VII and VIII.

U.S. quarantine notes

This species was intercepted at U. S. ports-of-entry 6 times between 1995 and 2012, with specimens originating from Denmark, El Salvador, Italy, Mexico and The Netherlands. We also have examined specimens taken in quarantine from Japan (Agave, Crassula, succulent); Mexico (Chrysanthemum, Sedum); The Netherlands (Echeveria); South Africa (Euphorbia). ScaleNet lists hosts in 9 plant families. It is most commonly collected on Asteraceae and Crassulaceae. ScaleNet distribution records for P. defectus include Mexico and the The United States of America (California) in the Nearctic region, and France in Europe in the Palaearctic region. Several species of Phenacoccus other than P. defectus, P. franseriae Ferris , P. gossypii Townsend & Cockerell, P. hakeae Williams, P. helianthi (Cockerell), P. madeirensis Green, P. parvus Morrison, P. solani Ferris, P. solenopsis Tinsley and P. stelli (Brain) have been taken at U. S. ports-of-entry including: P. alleni McKenzie (Mexico, on Artemisia); P. avenae Borchsenius (Turkey, on Stachys); P. azaleae Kuwana (Japan, on azalea); P. graminicola Leonardi (New Zealand, on Feijoa); P. hurdi McKenzie (Mexico, on Dendranthema and Capsicum); P. indicus Avasthi & Shafee (Thailand, on Euphorbia); P. multicerarii Granara de Willink (Mexico, on unknown host); P. manihoti Matile-Ferrero (Central Africa and South America, on Manihot); P. nephelii Takahashi (Thailand, on Garcinia; Vietnam, on Nephelium); P. pergandei Cockerell (Japan and Korea, on Diospyros, Magnolia, Malus, Prunus, Punica, and Rhododendron); and P. persimplex Borchsenius (Kazakhstan, on Malus).

Important references

Ferris1950b; McKenz1967; WilliaGr1992.

Scalenet catalog and citation list

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  Phenacoccus defectus  
 Illustration by Ferris

Phenacoccus defectus

Illustration by Ferris

  Phenacoccus defectus

Phenacoccus defectus