Cherry blackfly

What is cherry blackfly?

Cherry blackfly is an aphid that sucks sap from the foliage of fruiting cherries and ornamental forms of Prunus cerasus, P. avium and P. padus during late spring and early summer.

Symptoms

• During late spring and early summer, the undersides of the leaves and the shoot tips are covered with shiny black aphids
• Leaves become severely crumpled and curled
• Later in summer the damaged leaves may dry up and turn brown
• Foliage becomes sticky with the sugary honeydew that aphids excrete, and a black sooty mould may develop
• Susceptible types of cherry will survive aphid damage, but they are likely to suffer from curled leaves in most years

Control

Non-chemical control

• Where an ornamental, rather than a fruiting cherry is required, the problem can be avoided by growing the less-susceptible Japanese types of flowering cherries

Chemical control

• Treatment is only feasible on trees small enough to be sprayed thoroughly. Such trees can be sprayed with Growing Success Winter Tree Wash or Vitax Winter Tree Wash in December to reduce the number of overwintering eggs
• Susceptible ornamental cherries can be sprayed with thiacloprid (Provado Ultimate Bug Killer Concentrate), acetamiprid (Scotts Bug Clear Ultra concentrate), thiamethoxam* (Westland Plant Rescue Bug Killer Ornamental Plants) in late spring, when aphids begin to appear on the foliage
• Fruiting cherries can be sprayed with organic pesticides, such as pyrethrum (Py Spray Garden Insect Killer or Scotts Bug Clear Gun for Fruit & Veg), or synthetic contact sprays deltamethrin (Bayer Provado Ultimate Fruit& Vegetable Bug Killer), lambda-cyhalothrin (Westland Pl;ant Rescue Fruit & Vegetable Bug Killer). These contact sprays will give poor results once the aphids have caused the leaves to curl. Systemic insecticides, such as acetamiprid (Scotts Bug Clear Ultra concentrate) or  thiacloprid (Provado Ultimate Bug Killer Ready To Use), are absorbed into the foliage and can reach concealed aphids when they feed 
• Once the leaves have become curled the damage is done and it is too late for effective spraying
• Do not spray during the open blossom period in order to protect bees

* Please note this product is being withdrawn. The withdrawal (in effect a ban) comes into force on 30 September 2013, but there is to be a period of grace to use up these materials by 30 November 2013. After this time it will be illegal to use them, any remaining products should be taken to a manned local authority household waste site where they should be handed over to the staff. For information on waste disposal sites see www.pesticidedisposal.org. It remains legal to use other neonicotinoid-based products that are not affected by the withdrawal. This withdrawal follows concern over their effects on bees.

Download

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

Biology

• Cherry blackfly overwinters on the tree as eggs, from which wingless aphids hatch in spring as the foliage develops
• Winged forms appear in June-July, and these migrate to wild flowers known as bedstraws, Galium species
• Infestations on cherries gradually die out during July, but damaged leaves remain visible for the rest of the summer
• There is a return migration from bedstraws in the autumn, when the winter eggs are laid