Scale insects are

Sap is a fluid that circulates through a plant's vascular system, in a similar way to blood moving through our veins. Phloem sap carries the sugars produced in the leaves by photosynthesis down to roots and other storage organs, as well as carrying minerals and hormones. Xylem sap is watery and transports nutrients absorbed by the roots upwards to the rest of the plant. Some plants leak sap from wounds or pruning cuts, and this is known as bleeding.

Adult females of this species mature in September or October, they are 5-7mm long dark brown and convex, immobile and attached to host plants stems. The adult male is winged and pinkish, at only 1.5 mm long it is rarely seen. Males die after mating but the females overwinter and produce white waxy egg masses in May or June. The egg masses are  usually only found on stems and the wax can be pulled out in long threads; these characteristics distinguish this species from other insects that produce white waxy coverings such as cushion scale, fluted scale, horse chestnut scale, woolly aphid and mealybug.

The eggs hatch in June-early July initially the nymphs (crawlers) are mobile before eventually settling down on one year old wood to complete their development.

Large populations of woolly vine or currant scale can leave heavy deposits of sticky honeydew upon which a black non-parasitic fungus sooty mould often grows. Affected plants may also lack of vigour.

The 5-7mm dark brown insects will be evident upon examination on stems and in spring white waxy egg masses are usually clearly visible.

Check susceptible plants frequently from spring onwards 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 late spring to early 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 

• 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
• It can be worth considering replacing heavily affected plants
• Encourage predators  in the garden, some ladybirds, parasitoid wasps and some birds will eat scale insects

Pesticides

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 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.

• For scales on deciduous plants including edible fruits, a plant oil winter wash (considered organic e.g. Growing Success Winter Tree Wash) can be used. This can control the overwintering scale nymphs in December-January when the plants are fully dormant
• The best time for summer spraying is late spring and early summer when the more vulnerable newly hatched scale nymphs are present 
• With grape vines, peel away the loose outer bark to expose the scales before treatment
• 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

Download

Pesticides for gardeners (pdf document)