Body elongate oval; covered by layer of white mealy wax; cottony ovisac covers body and is longer than body of female, sometimes as much as 10 mm long; probably with 18 pairs of lateral filaments, becoming progressively longer posteriorly, caudal pair almost as long as body. Occurring on leaves and stems of host.
This species was intercepted at U. S. ports-of-entry 9 times between 1995 and 2012, with specimens originating from Mexico. We also have examined specimens taken in quarantine from Mexico (Acacia, Nerium). ScaleNet lists hosts in 14 plant families. It is commonly intercepted on basil (Lamiaceae– Mint family). ScaleNet distribution records for P. helianthi include Mexico and the United States of America (West of the Rocky Mountains). Several species of Phenacoccus other than P. defectus Ferris, P. franseriae Ferris, P. gossypii Townsend & Cockerell, P. hakeae Williams, P. helianthi, 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).