Tortrix moth caterpillars

Tortrix moth caterpillars bind leaves together with silky threads and feed inside, they can also damage fruits. They can affect a range of plants and in a glasshouse can cause damage throughout the year.

Tortrix moth caterpillar on Photinia

Tortrix moth caterpillar on Photinia

Quick facts

Common name Carnation tortrix and light brown apple moths
Scientific name Cacoecimorpha pronubana and Epiphyas postvittana
Plants affected Many edible and ornamental plants both indoors and outdoors
Main symptoms Caterpillars feed within leaves bound together with silken threads
Most active April to September but all year round in glasshouses

What are tortrix moth caterpillars?

These small green caterpillars are the larval stage of moths belonging to a family called tortrix moths (Tortricidae). There are almost 400 species of tortrix moth in the UK but there are two which can feed on a wide range of plants and commonly cause problems in gardens and glasshouses; the carnation tortrix moth (Cacoecimorpha pronubana) and light brown apple moth (Epiphyas postvittana).

Symptoms

The caterpillars bind leaves together with silky threads and feed within this shelter causing damaged areas to dry up and turn brown. Fruit and flowers can also be damaged. In glasshouses damage can occur year round.

Control

Non-chemical control

  • Light infestations can be controlled by squeezing the bound leaves to crush the concealed caterpillars and pupae
  • Carnation tortrix and light brown apple moths can be monitored and may be kept in check by using pheromone traps. This is an open-sided cardboard box with a sticky sheet in its base. A pellet which releases a pheromone is placed on the sheet; this is the same chemical produced by females to attract males. In a confined space, such as a glasshouse, these traps may capture enough males to reduce the mating success of the females. These traps are available from some including Agralan 

Chemical control

  • If caterpillars are too numerous to be picked off by hand, spray with  pyrethrum (considered organic e.g. Defenders Bug Killer) or the synthetic insecticides deltamethrin (e.g. Provado Ultimate Fruit and Vegetable Bug Killer), lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), or cypermethrin (e.g. Py Bug Killer)
  • Early treatment is best since young caterpillars are more susceptible than the older larva
  • When using pesticides on edible plants make sure the food plant is listed on the label and follow manufactures instructions on maximum number applications, spray interval and harvest interval
  • Do not spray plants that are in flower, especially fruit trees, to avoid harming bees and other pollinators
  • Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener

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

Biology

Out of doors light brown apple moth has two overlapping generations during the spring and summer. Eggs are laid in batches on the leaves of host plants and hatch after about ten days. The caterpillars then feed with foliage sown together with silken threads and pupae where they have been feeding. In glasshouses and on houseplants the lifecycle can vary, with adults and caterpillars active from late winter until late autumn.

Carnation tortrix moth has a similar lifecycle to light brown apple moth but can breed continuously in glasshouses and on houseplants. 


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