TECHNICAL | PPC112 September 2023

Returning contributor, Partho Dhang, has a PhD in Zoology and is the author of ‘Urban pest control: a practitioner’s guide’. This time he’s sharing tips on less common insects that occasionally concern our clients. 

Asporadic pest is one that is not seen on a regular basis. They appear under certain conditions, or at certain times or in certain localities. Therefore, sporadic pests necessitate only occasional control. Control of these pests is based solely on the tolerance limits of the complainant. 

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Can we control sporadic pests?

Often, control is based on an emotional or aesthetic threshold rather than on financial or cost-benefit analyses. This happens because people are unfamiliar with these insects and think they may cause significant damage or endangerment through stinging or biting. 

As Comont (2016) explained, in the UK, section 79(1) of the Environmental Protection Act 1990 (as amended) states that “any insects emanating from relevant industrial, trade or business premises and being prejudicial to health or a nuisance” shall constitute a statutory nuisance and thus be subject to controls.

This wording indicates the two-limbed structure of legal nuisance: insects do not need to spread disease or provoke an allergic reaction to act as pests.

Often, the mere presence of insects within dwellings is enough to provoke a response (particularly those species seen as dirty or threatening in some way), and numerous papers report the increase in the prevalence of nuisance insects all over the world, including UK (Roy et al, 2009). 

Sporadic pests fall in a grey area, as they are not severe or wide-ranging enough to be classed as statutory nuisances. The distinction between statutory nuisance and non-statutory nuisance will vary on a case-by-case basis; an insect will be a statutory nuisance in some scenarios but not others, particularly in relation to the source and abundance of the insects (Comont, 2016). A practitioner’s knowledge and training are thus very important in this situation.

The key to solving problems with sporadic pests is to determine the source and cause of the problem and achieve control by physical or cultural means whenever possible.

Silverfish and booklice

The most common sporadic pests in the UK include silverfish (Lepisma saccharina) and booklice (Psocids), which are often discovered by homeowners. Both insects are strictly indoor pests, stay in damp areas and can cause a nuisance.

Silverfish are found in damp areas, commonly in kitchens and bathrooms. They are nocturnal and often get trapped in baths, basins or crockery as they cannot climb smooth surfaces.

The insect is capable of quick movement. They often damage paper items by feeding on residues of starchy substances such as glues, wallpaper paste and carbohydrate food debris. 

Booklice also feed on mould caused by damp conditions. They are often seen on the glue of book bindings or on damp cardboard, damp food (especially cereals) or the surfaces close to damp plaster inside buildings, carpets and wallpapers. 

Both these pests can be controlled by preventive measures (which can also achieve control). The method is to keep susceptible areas well-ventilated, lit and dry with adequate ventilation.

Also, sanitation of indoor spaces such as cupboards and bookshelves will ensure future infestation from occurring. 

Some of the pests pictured may be sporadic in places but regular in some other geographic regions of the UK. It is also interesting to note that changing climate can be a factor; some of them may shift from sporadic nature to become a regular nuisance pest (Roy et al 2009).

Sporadic pests can emanate from a wide range of sources, but it is expected that most complaints of nuisance will be from poultry and other animal houses, buildings on agricultural land including manure and silage storage areas, sewage treatment works, stagnant ditches and drains on relevant premises, landfill sites and refuse tips, waste transfer premises, commercial, trade or business premises, slaughterhouses and used car tyre recycling businesses etc. 

Many of the sporadic pests originate in gardens or from fields around homes and houses. Ladybug beetles feed on aphids and mealybugs and are beneficial in controlling plant pests. However, they can become numerous and enter structures in large numbers during the fall of the year. At that time, they are looking for a sheltered place to overwinter. 

Other insects like thrips, leafhoppers, types of stink bugs, boxelder bugs and many other beetles that invade structures are huge problems for customers and are often very complex to prevent, manage or control. 

The method of control can be cultural or physical, wherein they are prevented from entering the structure by installing screens and sealing cracks around windows, doors, siding, and utility pipes, behind chimneys, and underneath the wood fascia and other openings.

Other sporadic pests originate in decaying organic matter on the ground. Many of these are rather slow moving but invade in huge numbers. For instance, millipedes have mass migrations from their breeding grounds when weather or soil conditions change. Normally, millipedes are satisfied staying under logs and feeding on decaying leaves and stumps.

But when millions migrate through lawns, it can be a problem. The best way is to remove logs, woodpiles, dried leaves, mulches, etc, from the vicinity of structures. Caulking and sealing gaps in foundations and around windows and doors can help keep out millipedes. 

“Normally, millipedes are satisfied staying under logs and feeding on decaying leaves and stumps. But when millions migrate through lawns, it can be a problem.”

Insecticidal dusts can be somewhat effective against millipedes, but they should never be spread in areas where children or pets can contact them (always check the label!). At times, pitfall traps and sticky traps may be used. 

Some aquatic insects have massive emergences during certain times of the year. Mayflies and aquatic midges are known to completely cover buildings close to water. For example, I’ve seen a paper manufacturing plant close to the water that had problems with aquatic insects being embedded into their paper products, making the product unusable.

Mayfly outbreaks have made roads slick, causing accidents. 

Water management in and around the building, proper lighting, installing screens and in case of high population, use of insecticidal space spray as well as killing the breeding population by using an IGR is recommended.

Sometimes people just stumble onto an insect and think it is interesting. A Buprestid wood-boring beetle is really attractive. Another name for this type of beetle is a jewel beetle because it resembles many expensive metals and crystals, like gold and emerald.

The Buprestids are usually a metallic iridescent colouration, and their wing covers (elytra) have been used in making jewellery. They may be brought in by collectors and later escape to become a sporadic pest. These situations can sometimes be overcome by physical collection and releasing them in a specific natural environment.

Some non-native invasive pests can also fall under the sporadic category simply because of their intermittent occurrence. A report lists 282 non-native species as currently invasive in Great Britain (Roy et al., 2009), and these are estimated to have a direct cost of £1.7 billion per year (Williams et al., 2010).

As this cost is largely related to control measures, an increase in pest species could see a considerable rise in the financial burden of non-natives in the UK and around the world.

Sporadic pests can be just about any insect or arthropod people encounter either inside or outside. The variety of sporadic pests makes it difficult to prepare an answer to customers’ questions. In such cases, a practitioner’s awareness and training are essential to control occurrences. 

References

• Comont, RF (2016) Climate Change Effects on Urban Pest Insects, ed. Dhang P, CABI, pp1-15
• Roy, H., et al (2009) Nuisance insects and climate change.
• nora.nerc.ac.uk/8332/
• Williamson, M, (1996) Biological invasions. Chapman & Hall, London, UK