Scientific name Lauritrioza alacris
Plants affected Bay (Laurus nobilis)
Main symptoms Leaves develop curled leaf margins that are thickened and pale yellow.
Most active May to October
What is bay sucker?
The psyllids or plant suckers are a group of sap sucking true bugs (Hemiptera). There are more than 40 species found in Britain.
Bay sucker feeds on the foliage of bay during the summer, the nymphs can cause distortion to leaf edges.
- Bay tree leaves thicken, curl downwards at the margins and turn yellow; often only half of the leaf is affected
- The discoloured areas later dry up and become brown
- Small greyish white insects may be seen underneath or near the curled leaf margins
- The long term health of the plant is usually unaffected
Bay sucker can affect the appearance of bay but does not usually reduce the vigour of bay plants and so control is not necessary.
Check bay frequently from spring onwards so action can be taken before a damaging infestation 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.
- Often suckers do not affect the growth or vigour of plants and so can be tolerated
- Encourage predators and other natural enemies of suckers, in the garden, such as birds, ladybirds, wasps and ground beetles
- If necessary distorted leaves can be removed from the plant however, this may cause more damage than the insect
Pesticide controlThe RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.
- 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. 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 suckers. These pesticides have a very short persistence and so may require reapplication to keep sucker 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 against aphids (e.g. Ecofective Bug Control, RHS Bug and Mildew Control, SB Plant Invigorator and Westland Resolva Natural Power Bug & Mildew). These products contain some synthetic ingredients and so 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)
- A systemic containing the active ingredient Flupyradifurone (Provanto Smart Bug Killer) is available for use on ornamentals and selected edibles
- The systemic neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra) is also available
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.
Pesticides for gardeners (link downloads pdf document outlining pesticides available to gardeners)
Curled thickened bay leaves are often caused by the nymphal stages of the bay sucker when they suck sap from the young leaves during the summer.
- The winged adults are greenish brown and about 2mm long (less than 1/8in), and they overwinter in sheltered places
- In April to May, adult bay suckers emerge and start to feed, causing the leaf margins to begin curling over. Eggs are laid under the curling leaf margins
- The nymphs are grey, flattened wingless insects, whose bodies are covered with a white fluffy material
- Like the adults, the nymphs suck sap and increase the leaf curling and discoloration
- Two or three overlapping generations occur between May and September
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