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Black scale

  • Adults and nymphs. Parasitic wasp.
    Black scale (on citrus). Note the light brown crawlers, and a parasitic wasp on the right.
Scientific name

Saissetia oleae

Description of adult

Adult females are dome shaped, dark brown to black in colour, and about 2 mm across.

Immature stages

Tiny eggs are laid under the female. These eggs hatch into tiny, six-legged, cream coloured 'crawlers', mostly in summer.

Life history

After hatching the crawlers move up the stems and usually settle along the veins of young leaves. The crawlers moult after about four weeks and then migrate to the young stems and twigs. Here they will mature, developing protective brown shells, and lay eggs.

Distribution

Throughout Queensland.

Host range

Olives, citrus and gardenia.

Damage

Feeding damage is usually minimal however sooty mould commonly develops on the honeydew excretions from the scale, disrupting photosynthesis.

Control options

The predatory ladybeetle, Cryptolaemus montrouzieri, can be purchased and released in spring-summer. It is often naturally present in orchards but is susceptible to toxic insecticides. Ants often ´farm´ the honeydew and can keep the natural scale predators away.

´Crawlers´ do not have the impervious shell of the adult and can usually be killed with one or two applications of white oil about two weeks apart.

Chemical registrations and permits

Check the Australian Pesticides & Veterinary Medicines Authority chemical database and permit database for chemicals registered or approved under permit to treat this pest on the target crop in your State/location. Always read the label. Always observe withholding periods.