Houseflies and bluebottle flies on a breadfruit
Interacting with a customer recently, I learned he had not yet evaluated the free sample of Gumtree Traps’ Fly Trapp Jar I had sent him. Nor had he made his pest control company apply strips of Envu’s Quick Bayt on the walls outside his company’s warehouses as I had suggested, to reduce the external ‘fly pressure’.
Instead, he called me yesterday asking for a suitable insect light trap that would not create a hazard of aerial insect parts generated by a traditional fly killer. Or have the problem of odour from dead houseflies trapped on the glueboard of a fly catcher. It seemed his company considered the recurring cost of glueboards for flycatchers an unnecessary expenditure.
I was struck by his concern, which, while valid in its desire for a cleaner solution, entirely missed the fundamental principle of effective fly management. I asked the customer to evaluate the efficacy of using the Fly Trapp Jar and the Quick Bayt paint-on application in controlling houseflies at his company’s warehouses. I added that by managing houseflies outdoors, he could significantly reduce the number of flies entering the warehouses and, consequently, need fewer fly catchers and experience fewer issues with odours or perceived “unnecessary” costs.
My above experience is symptomatic of a widespread misconception within the Indian food industry’s approach to fly control, particularly when dealing with the seasonal spurt in housefly populations each summer and monsoon. There’s a pervasive belief that a single device, like an Insect Light Trap (ILT), can magically solve all fly problems. I sometimes feel that Indian food companies expect flycatchers to function as a giant vacuum cleaner that sucks up all houseflies around it, ridding the space of flies instantly! Sadly, fly management is neither simple nor flies easy to control using any single device in isolation. The Indian food industry’s misunderstanding about flycatchers leads to the inappropriate deployment of resources, ineffective results, and ultimately, wasted resources.
The Anatomy of a Misconception: Why ILTs Aren’t Fly Control Devices
To understand why an ILT, including advanced ones like our FLYght UV LED Insect Light Traps, cannot function as a primary fly control device, we must first understand the biology of flies and the physics of light attraction.
Houseflies (Musca domestica) are highly adaptable insects, driven by a complex set of instincts related to feeding, breeding, and survival.
While they are attracted to certain wavelengths of UV light, this attraction is only one small part of their overall behavioural repertoire.
- Limited Attraction Radius: The UV light emitted by an ILT has a limited attractive radius. Flies located far from the trap, or those preoccupied with other stimuli (like food odours or warmth), may never even perceive the light, let alone be drawn to it. An ILT cannot “pull” flies from an entire facility or a large outdoor area. It’s designed to attract flies within its immediate vicinity.
- Not All Flies Are Attracted Equally: While generally effective for houseflies and some other flying insects, not all species are equally phototactic (attracted to light). Furthermore, even within a species, factors like age, sex, physiological state (e.g., gravid females seeking egg-laying sites versus males seeking mates), and hunger levels can influence their response to light. A fly heavily focused on finding a food source might ignore the ILT’s light altogether if a more potent attractant (like exposed food or organic waste) is nearby.
- Fraction of the Population: Even in an ideal scenario, an ILT will only ever attract and trap a fraction of the total fly population present in an area. If a food facility has hundreds or thousands of flies due to external infestations or poor sanitation, a handful of ILTs will make a negligible impact on the overall population. It’s like trying to empty a swimming pool with a teacup. The number of insects any ILT attracts, traps, or kills will always be a small percentage of the total, making it inherently ineffective as a standalone control measure for a significant infestation.
- No Impact on Breeding Cycle: Perhaps most crucially, ILTs only target adult flying insects. They do nothing to address the source of the infestation: the eggs, larvae (maggots), and pupae that are developing in organic matter. Without disrupting the breeding cycle, new adult flies will continuously emerge, rendering any trapping effort futile in the long term. Hence, focusing on outdoor hygiene and source elimination is paramount in fly management.
Factors that Influence Insect Light Trap Catches: From Control to Monitoring
Indoor Insect Light Traps are best understood as the last barrier to flies landing on food inside a food business. Their performance is less about “control” and more about “detection” and “monitoring,” and their effectiveness in this role is significantly influenced by several external and internal factors that must guide their deployment and use by a food company.
- Location, Location, Location: A building situated close to a place that inherently generates high fly populations – such as a poultry farm, a large garbage dump, a meat processing plant, a fresh produce market, or a wet market – is intrinsically prone to chronic fly incursions. Such facilities will experience an influx of houseflies year-round, not just during certain seasons. In these high-external-fly-population scenarios, ILTs can trap houseflies indoors, but only when the internal fly population is not overwhelming. The primary focus in such environments must be on aggressive outdoor fly control and robust prevention measures to stop the vast majority of flies from entering the building in the first place. Relying solely on indoor ILTs here is akin to trying to bail out a sinking ship with a thimble while the hull is breached.
- Suitability of Trap Type: Fly killers (often referred to as Electronic Fly Killers or EFKs) and fly catchers (often called Electric Fly Catchers or EFCs) operate fundamentally differently. EFKs kill flies by electrocution, which can cause insect body parts to fragment and become airborne. Due to a current lack of stringent legislation in India that restricts the use of fly killers with the potential to contaminate the air with insect body parts, such ILTs are unfortunately still commonly used by many food businesses. However, leading food safety audit standards globally, increasingly followed in India, rigorously highlight the contamination risk from fly killers and strictly restrict their use in areas where exposed food is handled, prepared, or stored. It’s disheartening to see restaurants in India extensively using fly killers, despite the clear potential for food contamination by dismembered insect parts in the air. Fly catchers, which trap insects on a disposable glueboard, offer a safer alternative for sensitive food areas as they contain the trapped insects and their parts. However, they still serve a monitoring, not a primary control, function.
- Operating Cost Perception: Flycatchers do have an operating cost associated with regular glueboard replacement. The cost of glueboards is often seen as “unnecessary expenditure” by businesses, as my customer illustrated. However, this cost can be significantly reduced, and glueboards can last much longer, if the external ‘fly pressure’ on the building is effectively managed, and fewer flies gain entry indoors. When outdoor and entry prevention measures are robust, the few flies that do get inside are quickly trapped by ILTs, extending glueboard life and making the operational cost entirely justifiable as a critical monitoring expense. Food businesses must shift their focus to robustly reducing fly entry indoors; this foundational approach will naturally help to prolong the effective use of fly catcher glueboards and make them an economically sound monitoring tool.
The True Purpose: Insect Light Traps as Monitoring Devices
The above discussion on ILTs brings us to the core message of this blog post: The primary, indeed the most critical, role of ILTs is to monitor the flying insect population and its types in their vicinity. They can never effectively control fly populations in the way an outdoor baiting program or strict sanitation can.
Even food safety auditors, in their focus on compliance, sometimes overlook the profound utility of ILTs when used correctly.
ILTs serve as silent sentinels that provide invaluable data by highlighting:
- The rise in fly numbers: A sudden spike in trapped flies indicates a breach in your external defences or a new breeding source.
- The types of insects entering: Identifying the species helps tailor corrective actions. Are they houseflies, fruit flies, or drain flies? Each insect type points to a different potential source.
- The areas where such insects are entering a building can be pinpointed by the location of active ILTs with high catches. These locations often indicate entry points, such as unsealed doors, damaged screens, or even employee pathways.
When used specifically for monitoring, ILTs don’t just show you a problem; they highlight the specific, actionable steps needed to prevent continued insurgence of flies. The corrective actions indicated by ILT data—such as building repairs, the immediate removal of fly-breeding organic matter, changing employee practices that facilitate fly entry (e.g., propping open doors), or improving waste management—are the true drivers that lead to a reduction in indoor fly populations and long-term control. Without these foundational actions, an ILT is merely counting the flies that got past your defences, not stopping them.
Flesh Fly on a leaf
Beyond the Trap: A Holistic Approach to Fly Management (Integrated Pest Management)
Based on the factors that influence ILT performance and to move beyond the “fly vacuum” myth, we share essential tips for ensuring effective, long-term fly management through a comprehensive and integrated approach.
Managing flies requires an Integrated Fly Management (IFM) strategy, where Integrated Pest Management (IPM) plays a crucial yet specific role.
- Eliminate Organic Matter (Sanitation is King): This is the single most important step. Rotting organic matter is the primary attractant for female adult flies seeking places to lay eggs. Hence, building exteriors and interiors must be kept meticulously free of such material. Sanitation for fly management needs:
- Use closed, sturdy garbage bins that are emptied frequently, especially in hot weather.
- Preventing the accumulation of any organic waste, including even gardening waste or leaf piles, near the building.
- Regularly cleaning loading docks, receiving areas, and waste disposal points.
- Ensuring that even sludge in effluent treatment plants is dried adequately and removed regularly, as it can be a significant source of flies if left moist.
- Promptly cleaning up spills and food debris inside the facility.
- Use Pesticide Baits and Bait Traps Strategically (Targeted Chemical Control): Effective pesticide baits, like Envu’s Quick Bayt, can be highly effective for outdoor fly control. These often require a single application (e.g., painted on non-porous surfaces away from food preparation areas) and periodic wetting to remain active and kill flies outdoors before they even reach your facility. Combine them with outdoor bait traps that attract flies through specific odours (like the Gumtree Traps’ Fly Jar) to minimise their population near your premises significantly. These tools are your first line of defence, reducing ‘fly pressure’ before it becomes an indoor problem.
- Fly Entry Prevention (Exclusion is Non-Negotiable): Physical barriers are critical aides to preventing fly entry indoors. These “structural defences” must be robust and regularly maintained:
- Window screens: Install fine mesh screens on all windows that open, ensuring they are free of tears or gaps.
- Automatic door closers: Ensure all doors, especially those leading to the exterior, are equipped with functional automatic closers.
- Double doors: Where feasible, vestibules with double doors create an airlock effect, significantly reducing the entry of flies.
- Air curtains: Properly installed and maintained air curtains above frequently used doorways create a barrier of air, deterring flying insects.
- Checking the effectiveness of fly barriers: Even when used, periodic checks of fly barrier functioning and effectiveness must be established and documented. More importantly, employees must be thoroughly trained not to obstruct or prevent the proper functioning of these fly barriers (e.g., propping open doors, damaging screens). Human error is often the weakest link in the chain.
- ILT Inspection and Corrective Action (The Monitoring Cycle): Despite comprehensive efforts to control them, flies can still be numerous. Fly monitoring is where Insect Light Traps come into their own. An accurate estimate of their indoor population and the effectiveness of your external controls can be obtained through strategically placed and regularly monitored ILTs.
4. Strategic Placement: Place ILTs away from direct sunlight, doorways, and competing light sources. Position them where flies are likely to enter or congregate, often near entry points or areas of concern, but not directly over exposed food.
5. Regular Checks: A weekly, or even more frequent, depending on the season, ILT tray or glueboard check is crucial. Regular ILT tray or glueboard check reveals not just the number but also the types of flies being caught.
6. Data Interpretation: A sudden increase in catches, or the appearance of new species, is an immediate red flag. Fly occurrence data must lead to prompt, targeted corrective action to prevent recurrence. Post-checking corrective action is the essence of ILT as a sentinel: it signals a breach, prompting an investigation into the source and its plugging to prevent future incursions.
7. Corrective Actions Based on ILT Data: If catches are high near a particular door, check its seal. If drain flies appear, investigate nearby drains. If a general increase occurs, inspect outdoor sanitation. These are the active steps that lead to actual fly reduction, making the ILT an invaluable diagnostic tool rather than a standalone solution.
As we end another housefly season in India, it is imperative to pause and reflect on the futility of deploying Insect Light Traps solely to control houseflies.
The common reliance on indoor and outdoor fly killers in food businesses, without a comprehensive strategy, often reflects a fundamental failure to use the right fly management principles.
Fly bait pesticide manufacturers, pest control companies, and indeed, food businesses themselves, must collaborate to educate and establish effective, multifaceted fly management programs using the principles outlined above.
Without rigorous outdoor hygiene, robust structural fly entry barriers, and a proactive approach to source elimination, no Insect Light Trap can truly “help” a food business in the long run. It will only ever reveal the extent of the problem, not solve it.
At Giridhar Pai Associates, we hope that more Indian food businesses will appreciate the nuances of fly activity and accordingly institute proactive, integrated steps to curb them, especially within critical food preparation areas.
High temperatures and humidity, which occur each summer and during the monsoon, are indeed ideal for housefly population explosions.
Still, the simple, comprehensive steps we have outlined will empower any food business to genuinely keep flies out by intelligently relying on Insect Light Traps as indispensable sentinels in their overall pest management strategy, rather than expecting them to be an all-in-one fly vacuum cleaner.
Embrace the monitoring power of ILTs but remember that the real fight against flies occurs outside and through meticulous outdoor facility management.