Symptoms
Large greyish green aphids, about 4-5mm long, form dense
colonies in early summer on the underside of leaves and on
the flower spikes. Populations peak in numbers from late May
to July. The foliage becomes sticky with honeydew excreted
by the aphids and a whitish waxy deposit from their bodies
also coats the leaf surfaces. The impact of this sap-sucking
insect can be so great that plants may wilt and die. All types of lupin are susceptible.
Cause
This aphid is native to North America and was first detected in England in 1981. It has now spread throughout Britain and elsewhere in Europe. The aphids are present on lupins throughout the year and overwinter in relatively small numbers on the basal buds. In summer winged forms develop and fly away to infest new plants.
Control
There is no non-chemical control, apart from hand picking, as unfortunately ladybirds, hoverfly larvae and parasitic wasps - the natural enemies of most aphids - show little interest in this species.
Inspect plants regularly during the growing season and take control measures before a damaging level of infestation develops.
Apply insecticides in the evening if the plants are in flower to avoid harming bees. Suitable insecticides include imidacloprid (Provado Ultimate Bug Killer concentrate), thiacloprid (Provado Ultimate Bug Killer Ready To Use), acetamiprid (Scotts Bug Clear Ultra concentrate) or bifenthrin (Doff All-In-One Garden Pest Killer, Bayer Sprayday Greenfly Killer Plus or Scotts Bug Clear Gun).
Organic products that contain pyrethrum (Py Spray Garden Insect Killer, Doff All in One Bug Spray or Scotts Bug Clear Gun for Fruit & Veg), or fatty acids (Bayer Organic Pest Control, Doff Greenfly and Blackfly Killer or Greenfingers Organic Pest Spray) will also give some control but need more frequent application.