Scurfy rose scale
Small white sap sucking scurfy rose scale insects can encrust rose (Rosa) and occasionally blackberry (Rubus fruticosus) stems.
Scientific Name Aulacaspis rosae
Plants Affected Roses (mainly species Rosa) and blackberry (Rubus fruticosus)
Main Symptoms Small flat whitish brown scales on stems
Most Active Spring and summer
What is scurfy rose scale?
Scale insects are sap sucking true bugs belonging to several families in the Hemiptera. Typically the adults are immobile having a flattened or raised appearance, with no visible legs. They often look like a ‘scale’ on a leaf or stem, many species produce a white wax often covering egg masses. There are more than 100 species found in Britain, 26 of which have been introduced. More than 25 species can be found in gardens or on houseplants.
Like all scale insects scurfy rose scale is a true bug that feeds on plant sap. As adults they are immobile and covered in a waxy ‘shell’. Male scales are flat, narrow greyish white scales, up to 1mm in length. Female scales are pear-shaped and up to 2.5mm long. Eggs are laid in July or early August and hatch in August to September.
The crawler nymphs are orange and wonder around on plant material and can be distributed from plant to plant in wind currents. The nymphs soon become sedentary developing into scales. In this species the male scales develop into winged adults in May or June, the females remain under the scale. Mating occurs in May or June.
Check roses and blackberries frequently so action can be taken before a damaging population has developed. When choosing control options you can minimise harm to non-target animals by using the methods in the non-pesticide section below. Pesticide treatments are likely to kill natural enemies and are only likely to be successful if the entire plant can be reached.
Light infestations are of little consequence and can be tolerated, but heavy attacks can be dealt with in mid to late summer when the more vulnerable newly-hatched scales are present. Note that dead scales can remain firmly attached to the plants. The success of any treatment can be gauged by the extent to which new growth remains free of scale insects.
- Where possible tolerate populations of scale insects. Well-tended healthy plants are able to tolerate light populations of these insects and so they do not necessarily require control
- Adult scales and egg masses can be removed when seen but this may not reduce large populations
- Scurfy rose scale can be difficult to control, replacing severely infested plants can be considered
- Encourage predators in the garden, some ladybirds, parasitoid wasps and some birds will eat scale insects
The RHS recommends that you don't use pesticides. Most pesticides (including organic types) reduce biodiversity, including natural enemies, impact soil health and have wider adverse environmental effects.
Where you cannot tolerate scurfy rose scale, manage them using the information above as your first course of action.
Pesticide treatments are likely to kill natural enemies and so reduce the likelihood of natural control and can lead to resurgence of the target animal.
The shorter persistence pesticides (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife.
The pesticides listed are legally available in the UK. This information is provided to avoid misuse of legal products and the use of unauthorised and untested products, which potentially has more serious consequences for the environment and wildlife than when products are used legally.
Always follow the instructions on the products. For edible plants, make sure the food plant is listed on the label and follow instructions on maximum number of applications, spray interval and harvest interval.
Homemade products are not recommended as they are unregulated and usually untested.
Be aware that products such as Neem oil are not registered for use in the UK and we cannot advise on their use.
Plants in flower must not be sprayed due to the danger to bees and other pollinating insects.
- The best time for summer spraying is August to September when the more vulnerable newly hatched scale nymphs are present
- Organic sprays, such as natural pyrethrum (e.g. Bug Clear Ultra 2, Neudorff Bug Free Bug and Larvae Killer) or plant oils (e.g. Vitax Plant Guard Pest & Disease Control, Bug Clear Fruit and Veg) can give good control of scale insect nymphs. These pesticides have a very short persistence and so may require reapplication to keep scale numbers in check. Plant oil products are less likely to affect larger insects such as ladybird adults
- Plant invigorators combine nutrients to stimulate plant growth with surfactants or fatty acids that have a physical mode of action (e.g. Ecofective Bug Control, RHS Bug and Mildew Control and SB Plant Invigorator). These are not considered organic
- Further information about the use of pesticides available for management of scale is available on the pesticides for gardeners leaflet
Pesticides for gardeners (pdf document)
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