Scurfy rose scale

Small white sap sucking scurfy rose scale insects can encrust rose (Rosa) and occasionally blackberry (Rubus fruticosus) stems, giving plants an unhealthy appearance.

Rose scurfy scale on rose

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 insect infestations can completely encrust parts of rose stems, giving an unhealthy appearance. Heavy infestations can reduce plant vigour although unlike some other scale insects this species does not produce honeydew.

Control

Scurfy rose scale can be difficult to control, replacing severely infested plants can be considered.

Non-pesticide control

Well-tended healthy plants are usually able to tolerate light infestations. The scales can also be scraped off the stems.

Pesticide control

The waxy covering produced by scales gives them some protection from insecticides and the best results are achieved by spraying against the newly hatched crawlers in August or September.

  • 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 infestation
  • Organic sprays, such as natural pyrethrum (e.g. Bug Clear Gun for Fruit & Veg, Ecofective Bug Killer), fatty acids (e.g. Solabiol Bug Free, Doff Greenfly & Blackfly Killer) or plant oils (e.g. Vitax Organic 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 insects in check. Plant oil and fatty acid products are less likely to affect larger insects such as ladybird adults
  • More persistent insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Pest Killer), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug 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
  • Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener
  • Do not spray on or near plants in flower due to the danger to pollinating insects

Provided manufactures instructions are followed especially regarding maximum number of sprays and harvest interval infested blackcurrants can be treated with some formulations of deltamethrin, lambda-cyhalothrin and organic products.

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)


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