Red scale is the most widespread pest of citrus in New South Wales.
Females have four, and males five, development stages.
All stages are sessile (non-free-moving) except the early part of the first stage (crawlers) and adult males (winged).
The scale cover of the female is circular (about 2 mm diameter), whereas that of the male is elongated.
The colour of the scale cover changes from white in the first stage to reddish brown in later stages.
Depending on temperature, red scale has two to five generations per year in NSW.
It infests leaves, fruits, twigs and limbs of all varieties of citrus.
Check five fruits per tree during October–March.
Take appropriate actions if 10% or more of fruits of early varieties are infested, or 15–20% or more of later varieties are infested. Appropriate actions include releasing parasitic wasps and the application of petroleum spray oil.
When choosing the latter option, time the spray when young scales are predominant.