Using Steinernema feltiae for the control of codling moth

There are several key species used in insect control – mainly at the larval stages of pests such as lepidoptera beetles and flies (the larval stages of the pest being more vulnerable to infection by the nematodes).

Despite being extensively studied in academia for centuries, we are only really just starting to scratch the surface on what can be done with some of these nematode species in terms of pest control, and Koppert is investing a considerable amount of research and development work in this sector, to help growers use nematodes easily and efficiently to control a wide range of crop pests. 

Reducing hibernating larvae

Codling moth (Cydia pomonella) remains one of the most important insect pests in apples and pears, particularly given the frequent occurrence of a second generation in late summer.

Research carried out by Koppert France has proven that autumn treatments with entomopathogenic nematodes can reduce hibernating codling moth larvae by up to 80%, with fruit damage at harvest the following year reduced by 60–80%.

These entomopathogenic nematodes, specifically the species Steinernema feltiae (product name Capirel) are applied to the larval stages of the pest during their descent from the trees in late summer/early autumn, with a repeat application before larval hatch in spring (late March–early April).

Capirel has also been proven to have good effects against apple sawfly (Hoplocampa testudinea), when applied to fruitlets on the orchard floor following the June drop or fruit thinning. The product also currently has plum fruit moth (Cydia funebrana), summer fruit tortrix (Adoxophyes orana) and red belted clearwing moth (Synanthedon myopaeformis) on the label, with more pests due to be added in future.

The species Steinernema feltiae exhibits both ‘cruising’ and ‘ambushing’ behaviour in seeking out suitable hosts. The nematode can detect and move towards its victim via a film of water (this is why leaf and soil wetness is important) to enter the body of the target pest through natural openings.

Once inside, the nematode releases toxic Xenorhabdus bacteria which induce septicaemia and death of the host within 2–4 days. The nematodes feed on the symbiotic bacteria and multiply inside the insect host.

After 2–3 weeks, the nutrients from the insect carcass are used up and the nematodes develop into infective juveniles (this is the most mobile and infective form). They will leave the insect if the environment is sufficiently moist to seek new hosts but stay inside the insect host if it is dry.

Steinernema remains effective at temperatures above 10°C and, if inside their original host,
can survive freezing. 

Integrated pest management

Capirel, as a natural insecticide based on the entomopathogenic nematode species S. feltiae, can form an important component of an integrated pest management programme.

The pack size consists of 3,000 million (three billion) infective juveniles (four packs of 750 million) which is enough to treat 2ha at a rate of 1.5 billion nematodes/ha. 

The nematodes come in a gel formulation which is easy to mix with water. The solution is best made up by adding each gel pack to two litres of tepid water first, gently mixing and allowing to stand for 20 minutes, before adding to the spray tank and making up the volume. Continuously agitating the solution during application will help ensure the nematodes are applied evenly. 

Use of an approved adjuvant such as Addit will help improve retention, spreading and penetration. The nematodes are best applied in a water volume of 1,000–1,500-litres/ha mixed with Addit at a rate of 0.125% v/v (125ml/100-litres).

Applications should be made on a wet day when there is plenty of leaf and soil moisture and low UV levels. Fortunately, such conditions are usually not hard to achieve in the UK climate in autumn and early spring, although evening or night-time spraying is recommended.

Autumn treatment

For autumn treatment of codling moth, apply when soil temperatures are consistently above 10°C and moisture is adequate.

Targeting the base of the tree using the lower nozzles on the airblast sprayer, will ensure the nematodes are directed to where the pest is most likely to be taking up its winter refuge. A second treatment can be applied in early spring (March), before pupation (which is usually around blossom time) and emergence of adult moths. 

For other pests (summer fruit tortrix and red belted clearwing) which are species that pupate (and stay) on the tree in late winter, spraying the tree canopy (including all scaffold branches and trunk), during September and October, rather than the soil beneath, is preferable.

Nematodes are easy to apply using conventional spray equipment. Nematodes can be tank mixed with many other products, although it is best to avoid mixing with fertilisers (especially nitrate).

The Koppert One Side Effects app (free and easy to download from www.koppert.co.uk/koppert-one) can help to determine which products are compatible for co-application. 

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