Fact Sheet: Cottony cushion scale

Scientific name

Icerya purchasi (Hemiptera: Margarodidae)

Similar species

cottony camellia scale, Pulvinaria floccifera

Icerya genistae

Icerya koebelei

Distribution

United States: widespread throughout the U.S.

Worldwide: Australia, Fiji, French Polynesia, Guam, Kiribati, Marshall Islands, New Caldonia, New Zealand, Forfolk Island, and Northern Marianas Islands.

Native to Australia.

Diagnostic characteristics

Adult females

7 - 9 mm (0.28 - 0.35 in.) in length. With ovisac, can appear 10 - 15 mm (0.4 - 0.59 in.).
Reddish-brown to yellow bodies covered with thick white or cream-colored wax.
Conspicuous elongated white egg case (ovisac) with 14 - 16 fluted ridges projecting from one side of the body.
The ovisac is approximately 2 - 2.5 times the length of the actual body.
Fragile crystalline rods protrude from the edges (margins) of the body.
Wingless.
Antennae composed of 11 segments.
The ovisac is a long waxy-fibered substance resembling cotton. It is extruded from glands at the rear of the abdomen to protect newly laid eggs.

Adult males

Approximately 3.18 mm (0.125 in.)
Dark red body; dark colored antennae and legs; shiny, black, diamond-shaped patch on top of middle body segment (thorax).
Gnat-like appearance.
Dark brown wings with a red vein branching once into two smaller veins.
Antennae have 10 segments but may appear to have 19 segments. Antennae are long and thin with tiny whorls of hair-like setae surrounding each antennal segment, except the basal segment.

Immature females

Three nymphal instars.
Red body with lemon yellow wax; black legs and antennae.
Elongated and convex shape.

Immature males

Characteristics similar to immature females.

Eggs

Red.
Oblong.
Contained within a cottony-appearing ovisac.

Hosts

Citrus hosts:

All Citrus species and their hybrids.

Non-citrus Hosts:

A partial list includes:

Acacia spp.
apple, Malus domestica
apricot, Prunus armeniaca
avocado, Persea americana
coconut, Cocos nucifera
coffee, Coffea arabica
fig, Ficus carica
guava, Psidium guajava
grape, Vitis spp.
mango, Mangifera indica
peach, Prunus persica
pepper, Piper nigra
Pittosporum spp.
pomegranate,Punica granatum
Rosea spp.
quince, Cydonia oblonga
walnut, Juglans regia

Host damage

Fruits

Occasionally infested.
Honeydew excreted by mealybugs coats the outside of fruit and promotes the growth of sooty mold fungus that inhibits photosynthesis, weakens the plant, and makes fruit unattractive.

Leaves

Often infest older leaves.
Can cause yellowing and premature loss.

Twigs

Young shoots can be killed when heavily infested by scales.

Biology

Adults can be found on the branches or trunks of trees. Cottony cushion scale females have both male and female sexual organs (hermaphrodites) and can produce female offspring asexually through parthenogenesis. Eggs (600 - 800) are contained within an ovisac attached to the body of the female. Mobile crawlers hatch from the eggs, disperse to a suitable leaf vein, and begin to feed. Cottony cushion scales retain their legs, eyes, and antennae for their entire life and remain mobile. Older instars move to the twigs, branches, or trunk to feed. Males are rare and exist in the species to allow the scale to reproduce sexually producing both females and males. Cottony cushion scales can have 2 - 3 generations per year.

Comments

The cottony cushion scale is a serious pest of citrus but is well controlled by the predatory vedalia beetle, Rodolia cardinalis.

All phloem-feeding, honeydew-producing pests have the potential to be tended by ants. The ants feed on the honeydew excreted by the pest and protect the pest from natural enemies. This protection can disrupt biological control programs.

References

Baker, J.R. 1994. Cottony cushion scale. N.C. State Univ. (http://www.ces.ncsu.edu/depts/ent/notes/Ornamentals_and_Turf/shrubs/note51/note51.html).

Ben-Dov, Y., D.R. Miller, and G.A.P. Gibson. 2009. ScaleNet database, life histories. (http://www.sel.barc.usda.gov/scalenet/lifehist.htm).

Butcher, C.F. 1983. Cottony cushion scale, Seychelles scale, and Egyptian fluted scale. Advisory leaflet 16. South Pacific Commission. (http://www.spc.int/pps/PDF%20PALs/PAL%2016%20Scales%201983.pdf).

Drees, B.M., and J. Jackman. 1999. Field guide to Texas insects. Gulf Publishing Company, Houston, Texas. (http://insects.tamu.edu/fieldguide/bimg116.html).

Ebeling, W. 1959. Subtropical fruit pests. Univ. Calif., Division of Agricultural Sciences.

Essig, E.O. 1938. Injurious and beneficial insects of California. State Commission of Horticulture, California.

Grafton-Cardwell, E.E. 2002. Stages of the cottony cushion scale (Icerya purchasi) and its natural enemy the vedalia beetle (Rodolia cardinalis). Pub. 8051. Univ. Calif., Division of Agriculture and Natural Resources. (http://anrcatalog.ucdavis.edu/IntegratedPestManagement/8051.aspx ).

Grafton-Cardwell, E.E., and M.L. Flint (eds.). 2003. Pest notes: Cottony cushion scale - Integrated Pest Management for Home Gardeners and Landscape Professionals. Pub. 7410. Univ. Calif., Agriculture and Natural Resources. (http://www.ipm.ucdavis.edu/PDF/PESTNOTES/pncottonycushionscale.pdf).

Grafton-Cardwell, E.E. 2008. How to manage pests citrus cottony cushion scale, scientific name: Icerya purchasi. Univ. Calif. IPM Pest Management Guidelines: Citrus, UC ANR Publication 3441(http://www.ipm.ucdavis.edu/PMG/r107301611.html?printpage).

Hamon, A.B. and T.R. Fasulo. 2005. Featured creatures fact sheet: Icerya purchasi Maskell (Insecta: Hemiptera: Margarodidae). EENY-034. University of Florida. (http://entnemdept.ufl.edu/creatures/fruit/cottony_cushion_scale.htm).

Miller, D.R., A. Rung, G.L. Venable, and R.J. Gill. 2007. Scale Insects: Identification tools for species of quarantine significance. CBIT Publishing, Queensland, Australia (http://www.sel.barc.usda.gov/ScaleKeys/ScaleInsectsHome/ScaleInsectsHome.html).