Control methods (Fruit tree tortrix moth)

Chemical control

Control with indoxacarb (Steward or Explicit), spinosad (Tracer) or the synthetic pyrethroid deltamethrin (Decis Forte etc):

Indoxacarb (Steward or Explicit), spinosad (Tracer) and the synthetic pyrethroid insecticide deltamethrin (Decis Forte etc) are approved for control of tortrix moth and other caterpillars in apple orchards in the UK.

Synthetic pyrethroid insecticides, which are very effective against the pest, should be avoided because they are harmful to predatory mites and other natural enemies.
Chlorantraniliprole (Coragen) is thought to offer incidental control when applied against codling moth.
First generation caterpillars may be controlled by a spray of one of these insecticides timed to coincide with the onset of egg hatch.
The first threshold pheromone trap catch (30 moths/week) indicates the date when egg laying commences.
The first insecticide spray should be applied about 2 weeks later.
These insecticides will also control codling moth which flies slightly earlier than fruit tree tortrix moth and sprays of these insecticides applied for codling moth usually also give good control of fruit tree tortrix moth.

Control with the insect growth regulator pyriproxyfen (Harpun):
Pyriproxyfen is an insect growth regulator (IGR) that mimics juvenile hormone. Juvenile hormone is a necessary chemical produced during an insect’s development, but becomes toxic when present during metamorphosis.

Pyriproxyfen is ‘bio-residual’ providing pest control several weeks after application.
Pyriproxyfen inhibits egg hatch, inhibits metamorphosis of nymphs to adults and reduces the fecundity of adult females (eggs laid are sterile).
The strategy is to target eggs or early larva stages to suppress the population.
There is no immediate lethal effect but effect can be seen during mating or with larval degradation during hatching.
Adsorption of the product is best when freshly laid eggs are treated up to 24 hours after laying.
Adsorption is reduced with egg ageing.
It should be noted that pyriproxyfen (Harpun) is new to the UK in 2020. It is recommended for use against codling moth so it is assumed that it may offer incidental control against fruit tree tortrix moth, but only experience of using it will confirm this.

Control with Bacillus thuringiensis:
See ‘Biological control’ below.

Insecticide resistance

Resistance of fruit tree tortrix to insecticides is not known to occur.

Cultural control

Trees which have a dense canopy and vigorous shoot growth tend to support greater populations of caterpillars. If shoot growth then ceases when caterpillars are young, due to water stress and/or a heavy fruit load, the caterpillars tend to move to feed on fruits, especially those in clusters, and damage intensifies.

Avoiding this situation by tree management reduced losses.
Furnishing the trees with artificial refuges for earwigs and other insect predators (see rosy apple aphid) is likely to help reduce young caterpillar populations.

Natural enemies

The fruit tree tortrix moth has many natural enemies. Parasitic wasps reduce populations to comparatively low levels in unsprayed orchards but parasites are less abundant in orchards sprayed with broad-spectrum insecticides.

Insectivorous birds
Tits especially pick overwintering larvae from bark, but do not forage specifically for the pest unless population densities are very high and for this reason are of limited value only.

Egg parasites
Parasitic wasps (Trichogramma sp.) attack the eggs but parasitism rates are generally low.

Larval and pupal parasites
Several parasitic wasps and flies parasitise fruit tree tortrix moth larvae or pupae.

Common species are Meteorus ictericus which develops inside the host larva before exiting the larva at the third instar stage, spinning a cocoon nearby. The host larva is not devoured entirely and remains alive for a period of time, eventually dying without further development.
Apanteles ater is another common internal larval parasite.

Predatory insects
Earwigs and predatory mirid and anthocorid bugs feed of eggs and young larvae.

Virus diseases
No virus diseases of fruit tree tortrix moth have been reported.

Biological control

A programme of weekly sprays of Bacillus thuringiensis (Bt) (Dipel DF) throughout the egg hatch period gives fairly good control but is costly compared to other insecticides.

Bt has to be ingested to act and is most effective in warm weather when caterpillars are feeding actively.
The bacterium produces a crystalline toxin.
The insect dies from the effects of this toxin rather than from pathogenesis due to the bacterium.
Bt is of short persistence as it is degraded by heat and UV light.
It is most effective against newly hatched larvae before they form leaf rolls in which they feed internally and are inaccessible to sprays.
The first spray should be applied at the onset of egg hatch which should be determined from pheromone trap catches and egg development sums calculated from the daily maximum and minimum air temperature.
Bt is not detected by conventional pesticide residue analysis.

Biotechnological control