Scale insects are a diverse group of insects that includes armoured scales, soft scales, mealybugs, felt scales and other groups. There are many species that damage nursery stock; some occur on a large number of plant species while others are more specific. One of the most challenging aspects of scale insect infestations is that low numbers of individuals can be very difficult to detect. Once favourable conditions occur, several individuals can rapidly increase in numbers and cause damage. Insecticides can sometimes be used to kill scales, but their remains often are left behind. It is important to monitor for scale insects early in the season and put in place proactive management actions to stop populations from building up. It is also critical to ensure mother stock are free from scales when propagative material is collected.
There are a large number of cultural practices that can assist in reducing the impact of scale insects, as well as insecticides and commercially available predatory insects. Details on their biology and these management strategies are discussed in the available on the Australian Plant Production Standard website.
Scale insects that you need to identify to assist in managing the pest can be sent to the diagnostic service Grow Help Australia, all production nurseries receive 6 free samples per year.
Figure caption: An infestation of Black Scale (Saissetia oleae)
Photo from pestid.com.au