Woolly vine or currant scale

Woolly vine or currant scale has a wide range of woody hosts including grape vine, peach, nectarine, currants, gooseberry, pyracantha and mountain ash. Honeydew and sooty mould occur on heavily affected plants.

Woolly vine scale (Pulvinaria vitis) with egg masses

Quick facts

Common name Woolly vine or currant scale
Scientific name Pulvinaria vitis
Plants affected A wide range including grape vine, peach, nectarine, currants, gooseberry and pyracantha
Main symptoms White egg masses, honeydew and sooty mould
Caused by Sap sucking scale insects 
Timing Spring and summer

What is woolly vine or currant scale?

There are many species of scale insects encountered by gardeners, they are sap sucking true bugs. Like other scale insects the adult woolly vine or currant scale are covered in a waxy ‘scale’ covering.

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.

Symptoms

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.

Control

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 starting with the methods in the non-pesticide control section. If this is not sufficient to reduce this insect 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 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 control

  • 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

Pesticide control

  • 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 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.

Download

Pesticides for gardeners (pdf document)
 
 


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