Using Beneficial Nematodes for Pest Control in UK Agriculture
Beneficial nematodes are microscopic organisms that can be used to control certain soil-dwelling pests as part of an integrated pest management programme.
Different nematode species target different pests, including slugs, leatherjackets and vine weevil larvae. Their effectiveness depends on matching the right species to the target and applying it under suitable soil and environmental conditions.
They are already well established in parts of horticulture, protected cropping and amenity production, with more selective opportunities in field crops where the biology, economics and application conditions are appropriate.
What are beneficial nematodes?
Nematodes are microscopic roundworms found naturally in soils and other environments.
Some species are plant parasites, but others are beneficial and can be used as biological control agents against particular pests.
The nematodes used for insect pest control are commonly described as entomopathogenic nematodes. Species within genera including Steinernema and Heterorhabditis seek out susceptible insect larvae in the soil and enter through natural openings or, in some cases, through the cuticle.
Once inside the host, they release symbiotic bacteria that multiply and kill the insect. The nematodes reproduce within the host before infective juveniles emerge and search for further suitable pests.
Different nematodes target different pests
Biological control with nematodes is highly species-specific.
A nematode used against leatherjackets will not necessarily control vine weevil or slugs, and differences in temperature, soil moisture and pest life stage can all influence performance.
This means selection should start with the target pest and its biology rather than with the nematode product itself.
Nematodes for slug control
Phasmarhabditis hermaphrodita is a parasitic nematode used for biological control of certain slug species.
It differs biologically from the entomopathogenic nematodes used against insect larvae and should not be assumed to have exactly the same mode of action.
After application to moist soil or growing media, the nematodes locate susceptible slugs and enter the area beneath the mantle. Infected slugs generally reduce feeding before they die, helping limit further crop damage.
Grey field slugs are among the species most susceptible, while effectiveness can vary with slug species, size and environmental conditions.
Where slug nematodes fit
Nematode-based slug control can target slugs below the soil surface as well as those that are active at the surface, which can be useful in situations where conventional baiting is difficult.
However, cost and the environmental conditions required for good nematode activity mean the approach is currently more suited to some high-value, horticultural and organic situations than routine use across large broadacre areas.
Where they are used, adequate soil moisture and suitable temperatures are important, and applications are generally best made away from strong sunlight and drying conditions.
Nematodes for leatherjacket control
Leatherjackets are the larval stage of crane flies and feed on roots and young plant material close to the soil surface.
They are particularly associated with grassland and turf, although damage can also occur in agricultural and horticultural crops where populations are high.
Steinernema feltiae is one beneficial nematode species used to target young leatherjacket larvae.
The nematodes locate susceptible larvae in the soil, enter the host and release symbiotic bacteria. Feeding stops following infection and the larvae subsequently die.
Timing is critical
Young larvae are generally more susceptible than larger, more developed leatherjackets, so application needs to be aligned with crane fly activity and larval development.
Soil temperature and moisture are also important because nematodes need a film of water around soil particles to move and locate their hosts.
Product-specific recommendations should always be followed, particularly because commercial nematode products may be authorised or recommended for particular crops, environments or uses.
Nematodes for vine weevil control
Vine weevil is an important pest in ornamental production, nurseries, soft fruit and other horticultural systems.
The larvae feed on roots below the surface and can cause severe damage before symptoms become obvious above ground.
Several beneficial nematode species can be used against vine weevil larvae, including Heterorhabditis bacteriophora and Steinernema kraussei.
The most appropriate species depends partly on soil or growing-media temperature and the production system.
Once applied to the root zone, the nematodes seek out susceptible larvae and infect them below the surface.
What affects nematode performance?
Beneficial nematodes are living organisms, so their performance depends heavily on application conditions.
Important factors include:
- correct identification of the target pest;
- selection of an appropriate nematode species;
- targeting a susceptible pest life stage;
- suitable soil or growing-media temperature;
- adequate moisture before and after application;
- protection from strong sunlight and drying conditions;
- correct storage before use; and
- appropriate application equipment and water volume.
The recommendation should therefore be based on the individual pest, crop and environmental conditions rather than a standard nematode programme.
Soil moisture and nematode movement
Moisture is particularly important because nematodes move through thin films of water around soil particles.
Very dry conditions can restrict movement and survival, while unsuitable temperatures can reduce activity.
Heavy or compacted soils do not automatically prevent nematodes from working, but soil physical conditions can influence how effectively they move through the profile and reach the target pest.
Maintaining appropriate moisture following application is therefore often an important part of successful use.
Applying beneficial nematodes
Nematodes are normally supplied as living infective juveniles in a carrier material and mixed with water before application.
Depending on the product and crop, they may be applied through irrigation or suitable spray equipment.
Application equipment needs to be appropriate for a living biological product, so filters, nozzles, pressure and agitation should be checked against the manufacturer's instructions.
Applications are generally made in dull conditions, during the evening or at another time when exposure to strong UV radiation and drying is reduced.
Compatibility with other crop inputs
Beneficial nematodes can fit alongside other crop protection and nutrition inputs, but compatibility should not be assumed.
Some plant protection products and fertiliser solutions may be compatible with particular nematodes, while others could reduce their viability.
Where tank mixing or close application timings are being considered, current product-specific compatibility information should be checked first.
Where nematodes fit within integrated pest management
Nematodes are one biological tool within a wider pest-management strategy.
Their use should be considered alongside pest monitoring, crop rotation, cultivation, soil management, varietal choice and authorised crop protection products where appropriate.
They can be particularly useful where:
- the target pest spends an important part of its lifecycle in the soil or growing media;
- the pest can be targeted at a susceptible life stage;
- environmental conditions support nematode activity;
- the economics suit the crop and production system; and
- a biological option complements the wider IPM programme.
The presence of a biological control option does not mean it will automatically be the most appropriate treatment in every situation.
How Agrii evaluates biological pest control
Biological crop protection is developing quickly, with new organisms, formulations and application approaches entering the market.
Agrii evaluates biosolutions to understand how they work, the conditions required for activity and where they can provide a repeatable response within commercial crop production.
This includes considering how biological products interact with established agronomy and crop protection programmes rather than assessing them in isolation.
The objective is to identify where a technology has a practical role and where conventional or alternative management may still be more appropriate.
A targeted biological approach
Beneficial nematodes provide an established biological control option for several important pests, but their success depends on correct pest identification, species selection, timing and environmental conditions.
For slugs, leatherjackets and vine weevil larvae, different nematodes and application approaches are required.
Used in the right situation, they can provide another useful component within integrated pest management.
Speak to your Agrii agronomist about where biological pest control could fit within your crop protection programme.
Disclaimer:
The above content is for informational purposes only and does not constitute agronomic advice. The subject of effective pest and disease management is vast and contains many variables which cannot be fully addressed in this space. Always seek professional advice.