Box Hedge Caterpillars

Further to earlier information provided by Firstport about the box caterpillar infestation which has caused some Buxus plants to die on the communal grounds of Repton Park, please note information taken from the RHS website about this subject:

What is box tree caterpillar?

Box tree caterpillars are the larvae of a moth that feeds on box (Buxus) plants. It is native to East Asia and it became established in Europe in 2007. Although adult moths were first found in the UK in light traps in 2008, it was not until 2011 that larvae were reported in private gardens in the home counties. By the end of 2014 the moth had become established in parts of London and surrounding counties; in many cases the caterpillars had caused severe defoliation indicating that the moth is likely to become a serious problem.

Symptoms

Gardeners are likely to become aware of box tree caterpillar when they find webbing and caterpillars on box plants. The pale yellow flattish eggs are laid sheet-like, overlapping each other on the underside of box leaves. Newly hatched caterpillars are greenish-yellow, with black heads. Older caterpillars reach up to 4cm (1¼in) in length and have a greenish/yellow body with thick black and thin white stripes along the length of the body. The pupae are concealed in a cocoon of white webbing spun among leaves and twigs.

The adult moth usually has white wings with a faintly iridescent brown border, although the wings can be completely brown or clear.

The moth has a wingspan of around 4cm (1¼in). The caterpillars eat box leaves and produce webbing over their feeding area.

Plants may also show patches of dieback which may be especially apparent on trimmed plants. This is not to be confused with dieback caused by the disease known as box blight

Non chemical control

Where practical, caterpillars should be removed by hand. A pheromone trap which can help monitor adult moth activity is available from several suppliers including Agralan.

The mixed nematode biological control sold as Fruit and Vegetable Protection may have some effect on the larvae

Chemical control

Extensive infestations can be treated with an insecticide. Thorough spray coverage is required if control is to be achieved. Forceful spraying is needed to penetrate silk webbing.

The contact pyrethroid insecticides pyrethrum (considered organic e.g. Bug Clear Gun for Fruit and Veg or Defenders Bug Killer,), deltamethrin (e.g. Provado Ultimate Fruit & Vegetable Bug Killer, Sprayday Greenfly Killer), lambda-cyhalothrin (e.g. Westland Resolva Bug Killer) may have some effect.

We hope you find the above information helpful if you are experiencing problems with the box caterpillar.

Please let us, or Firstport, know if you find any Box Hedge Caterpillars or evidence they have come back.

 

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