Scurfy rose scale

Small white sap sucking scurfy rose scale insects can encrust rose (Rosa) and occasionally blackberry (Rubus fruticosus) stems.

Rose scurfy scale on rose

Quick facts

Common Name Scurfy rose scale
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?

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.

Symptoms

Scurfy rose scale can completely encrust parts of rose stems. Large infestations can reduce plant vigour although unlike some other scale insects this species does not produce honeydew.

Control

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 starting with the methods in the non-pesticide control section. If this is not sufficient to reduce the damage to acceptable levels then you may choose to use pesticides. Within this group the shorter persistence pesticides (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife than those with longer persistence and/or systemic action.
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

Non-pesticide control

  • Where possible tolerate populations of scale insects. Not all scale insects affect the growth of plants 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

Pesticide control

  • 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 Gun for Fruit & Veg, Neudorff Bug Free Bug and Larvae Killer), fatty acids (e.g. Solabiol Bug Free, Doff Greenfly & Blackfly Killer) or plant oils (e.g. Vitax Plant Guard Pest & Disease Control, Bug Clear for 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 and fatty acid 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, SB Plant Invigorator and Westland Resolva Natural Power Bug & Mildew). These are not considered organic
  • More persistent contact-action insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer, Provanto Sprayday Greenfly Killer) and cypermethrin (e.g. Py Bug Killer)
  • The systemic neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra) is also available
Follow label instructions when using pesticides. On edible plants make sure the food plant is listed on the label and follow instructions on maximum number applications, spray interval and harvest interval
Plants in flower should not be sprayed due to the danger to bees and other pollinating insects
Inclusion of a pesticide product does not indicate a recommendation or endorsement by RHS Gardening Advice. It is a list of products currently available to the home gardener

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Pesticides for gardeners (pdf document)


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