PPC116 | Opinion
What type of insect resistance do we have in the UK? Are we dealing with resistance or treatment error? What role does IPM have in reducing callbacks?
At PestEx 2024, in part of the Big Debate series, we asked a panel of industry experts to weigh in on resistance issues in insect pest management.
Pete Bowers-Davis PBD, Rich Faulkner RF, John Horsley JH, and Avril Turner AT.
JH Do we have multiple types of resistance in insects? If so, what are they?
RF There are four different types of resistance: ‘behavioural’, when insects migrate away from chemicals or don’t eat the bait. ‘Cuticle thickening’, a genetic mutation resulting in the production of thicker wax. ‘Metabolic’, a genetic mutation, which means they can metabolise the chemicals, so they are no longer lethal. And ‘target site’, where the insecticide no longer binds to the target site, which is often part of the nervous system.
JH How widespread is insect resistance?
AT It’s not as widespread as assumed. It’s usually down to a key genetic mutation in the insect.
PBD We do see examples of it. We had a bed bug contract for a large national hotel chain. In the first year, we found bed bugs in key harbourage areas around the hotel, all in the same spots within the room.
Two years later, they were not to be found in those places. They wouldn’t sit on the headboard or base of the bed. They were moving away from prime harbourage areas because of the pest treatment.
RF We need to be asking is it resistance to the chemical or is it the way the chemical is being used? Are staff looking or not looking at labels? Applying to the wrong areas?
If you’re applying to a surface that’s a higher temperature, it’s going to affect the efficacy of that chemical. It’s looking at the user.
How do you store chemicals? Are they even in date? Have they been in the back of your van and been frozen? Are they going to be as effective? The formulation might not work on certain surfaces.
PBD It’s easy to end up taking a punt on dilution rates. A lot of it is about the treatment plan, the prep work or chemical storage.
It’s also about working with the customers. You can go to a hotel to treat a room, then the customer says after you left, they gave it a good clean and wipe down, which they didn’t realise will have also removed the chemical treatment – so it’s not always about resistance.
JH Pest control requires such a vast amount of information anyway, but it’s about getting that out there. There are all kinds of issues you may face – someone hoovering up after you’ve gone – there are lots of factors that can affect this.
PBD Work through every job from start to finish. When we’re dealing with bed bugs, we talk it through with the customer.
But we can give them advice to wash all the bedding and clothing, then run through the treatment plan only to find they’ve bagged all their clothes, moved them to another room, but not got round to washing them before they’ve started bringing them back into the bedroom.
JH Could failure in treatments be operator error?
PBD Between us, we’ve only seen real resistance to a chemical once or twice. So, something else out there is going wrong.
Everybody says it’s resistance but if no one is really seeing resistance at the level it’s perceived to be, it’s something else. It’s the mixing, dilution, prep, or not understanding the lifecycle.
AT There are isolated areas of resistance – they are there, but I just don’t think they’re as widespread as we perceive.
Planning and using other chemicals as well – if we are using all these things, we wouldn’t experience resistance because we would be killing them off without the use of chemicals, so resistance wouldn’t be a factor anyway.
RF Most of it is how you’re treating and what the plan is. If you plan properly it will work. We’ve got fewer ingredients than we had when I started.
But we need to be clever with the use of the chemicals we have and use some intelligent planning.
JH Are we using things like diatomaceous earth? I used to encourage technicians to speak to other techs or manufacturers’ technical people.
They are the people that are available to help you with these things. It highlights areas where there’s resistance. It puts a marker there.
AT There’s a really simple test for chemical resistance. Put the bed bugs in a pot with the chemical and leave it for an hour. If the insects are dead, there’s no resistance.
RF There is a facility for mosquito resistance and chemical testing. It can take up to a decade to get a chemical to market. So, resistance is covered in that as well. There are companies out there that will do resistance testing as well.
Talk to your manufacturers and distributors. We are here to help, we want to help, and we want you guys to be successful. Talk to other people in the area who might be rotating chemicals or who might have come across something that you don’t know about.
JH Are there resistance hotspots?
RF It all comes down to the sampling and getting that data. It’s not very well-mapped. ‘Insects’ covers tonnes of species, so it’s not something that we can easily gather data on.
AT If you don’t hear people talking about it and don’t have this sampling coming in, then clearly it’s working most of the time. However, it’s definitely possible to get some that are resistant and some that are not resistant in the same population.
“The only sort of other new resistance being reported now is in house flies. There’s potential in all insects for all types of resistance, but essentially we don’t have the data.”
JH How important is IPM?
RF It’s really about being forensic, alternating chemicals, having a plan. We talk about IPM, but it should be integrated ‘product’ management.
There’s not one thing you have that’s a silver bullet. Always have a plan B and a plan C.
PBD It’s so important to use different treatment methods, not just look to chemicals.
Bed bugs are the big one for everybody. We remove all the bedding in a silk bag. If we move to that, we’re taking 60% of the infestation away on the first visit. Use a bed bug vacuum.
Taping – we used to do that in aircraft. You can remove so many before you even apply that insecticide. I’ve seen techs walk in, soak everything in insecticide and that’s the way they operate.
It’s about thinking about why that treatment failed rather than immediately assuming it’s the chemical. It’s about how you’re treating and the environmental factors.
JH What about managing customer expectations? Do we do enough of this?
AT Customer education is really important. If it’s bed bugs and you’re suggesting they wash bedding, they need to understand that everything needs to be washed at least at 60°C and that washing at 30°C means some eggs could still survive.
It’s about good customer information – and making sure they tumble dry everything as well!
PBD We send out a prep sheet as soon as we get an enquiry. It includes what they need to do before and after the treatment. If the treatment isn’t successful, it’s almost always one of those things that hasn’t happened.
Questions include: When did you last de-flea your pet? We state very clearly that unless you follow that prep sheet, we can’t guarantee the success of any of our work.
RF We went to a hotel where there were tapestries on the walls. It was a nightmare. They need to do their bit, you need to do your bit. Look to the chemical, look at the dilution rate. Crack and crevice treatment – how do you work out the application rate? Are we over-applying the chemical?
It’s about the planning and making sure the customers are doing exactly what they need to do as well.
JH What about strong liquid concentrates in vans over winter and summer?
RF If you have a chemical store, keep it in the building. Maximum and minimum temperatures vary from chemical to chemical. It’s just being aware of that. We can’t do much about the weather.
AT The details are always on the label. Protect from frost, ventilation, not too warm.
PBD Say there’s a sprayer left in the van overnight. Chemical separation happens, you give it a shake, but do you really know the dilution rate? Ask yourself at what step has it gone wrong?
JH An insulated fishing box works well as a bund and inhibitor or bubble wrap.
JH Is all resistance really genetic?
RF Every animal can behave in a way that it shouldn’t and some insects appear to have become a lot more resistant in the way they move and act.
Cockroaches, for example – the old gels had simple sugars in them. Now they won’t eat this. We have to use more complex sugars because the old formulas – that were cheaper - won’t be approached by cockroaches.
Proper genetic changes don’t happen overnight, they can take thousands of years. In that case, resistance is possible but unlikely.
AT The only sort of other new resistance being reported now is in house flies. There’s potential in all insects for all types of resistance, but essentially we don’t have the data.
JH What are the key takeaways? We become educated around product use, we work on educating the customer and make sure that we rotate chemicals as part of an IPM.
Do you have anything to add to the issue of resistance?
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