Black scale

Scientific name

Saissetia oleae

Description of adult

Adult females are dome shaped, dark brown to black in colour, and about 2mm 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 4 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

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 1 or 2 applications of white oil about 2 weeks apart.

Chemical registrations and permits

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