iconThere are a few schools of thought about spider treatments, but as always it is important to identify which spider you are treating and your (customer’s) desired outcome. There are some people who claim you can only control spiders by direct contact at the time of treatment.  Some manufacturers have claimed their product has shown more than 18 months control in trials.  Others claim, and this is where I sit, that it is important to contact as many spiders as possible at the time of treatment but residual spider control is most likely achieved by controlling flies and moths, the spider’s prey.  Which is true?




Is identification important?  I believe it is, but only to the level where it helps you make the treatment a success.  There is little value in identifying a pest unless that identification gives you understanding of its life cycle, habits and potential danger and you can use that information to provide a better treatment.  It may be sufficient to identify some spiders as ‘webbing spiders attached to the house’ and to differentiate from Orb Weavers that may use the house as one anchor for their webbing.  Spider look-a-likes such as the ‘daddy long legs’, that are not susceptible to some treatments need to be identified if those products are to be considered for use.

Your desired outcome is determined by the requirements of the customer.  The customer that wants spider activity to be dampened down may be happy with a quick spot spray.  If they were expecting freedom from spiders because you offer them a 12 month warranty, they may be very disappointed.


Treatments for ground dwelling spiders, red-backs and webbing spiders will be very different.  If you write ‘spiders’ on the quote or invoice your customer will expect you to treat them all. Ground dwelling – eg funnel web.  Funnel webs are poisonous, the aim of this treatment is to dramatically reduce numbers without exciting the spiders to roam into ‘people’ areas.  A sub-lethal dose of a synthetic pyrethroid (SP) will cause funnel webs to roam and seek shelter, perhaps finding their way to a harbourage in someone’s shoe in the laundry.  Organo-phosphates (OPs) do not excite the spiders and are ideal to treat ground dwelling spiders.


Red-backs – or search and destroy!  Red-backs have a very characteristic untidy web, sticky at the top to catch prey and not sticky in the lower part as the living quarters.  Because these spiders can be so scattered, a thorough inspection for all sites of activity is essential.  For success, the spiders and their eggs must be controlled.  Where the webbing is on a house, the spider will often shelter inside the weep holes – these should be dusted using a powerful duster with a weep hole attachment.  More commonly we hear of red-backs in roof voids dropping from downlights. These may be treated by dusting or misting the roof void.  I prefer dusting with permethrin dusts, which are now registered for control of spiders.  The most common place to find red-backs on a service call is where they were before, indicating a thorough treatment was not carried out the first time.  SPs will flush red-backs from nooks and crannies.

Webbing spiders – you must differentiate between house-bound and garden spiders that attach their web to the house as an anchor.  There is little that can be done to control the garden spiders such as the Orb Weavers – and really who would want to even if walking through their web occasionally is uncomfortable.  The treatment of house-bound spiders is discussed in detail below.

Some OPs do not control ‘daddy long legs’

Are daddy long legs spiders?  “Urban Pest Management” describes thin legged ‘spiders’ that bounce their body when disturbed as Harvestmen, not true spiders.

When contacted in the past about Baytex not killing spiders, I would ask the complainant if the spider was daddy-long-legs.  Without exception, the answer was ‘yes’.  I do not know if this is common to other OPs.

Treatment of brick constructions compared to weatherboard houses.Which product(s) should you use?

Spiders hide inside weep holes and around window and door frames and surfeits of brick houses.  Weatherboard houses provide many more harbourages, often with cracks between each weatherboard.

The small droplet size and high spray pressure may help penetration into cracks and crevices but may cause spray drift.   

Two points to note:

1)  Product labels – many labels require double the amount of formulation if a pneumatic (hand pump) sprayer is used compared to a mechanical pump.  This is because you will use about twice the amount of total spray using your truck mounted pump compared to your Rega – so the same amount of active is delivered.  Some labels (eg Cislin) also differentiate rates on the basis of treating porous or non-porous surfaces, porous surfaces are half the product but double the spray volume compared to non-porous.  There is good logic behind that – you can only put so much spray onto a non-porous surface (eg painted weatherboard) before it runs off, whereas brick will absorb much more.  
Some labels, such as Biflex, promote a two part treatment for spiders – a crack and crevice treatment to draw spiders out of their nooks and crannies followed by an overall band spray of surfaces.  This has obvious advantages over a one-step coverall treatment, but how many pest managers go around a building twice?    

2)  You may consider using a solvent based SP for weatherboard houses and a SP – wettable powder, suspension concentrate or capsule suspension formulation – for brick homes.  
My reasoning for this is that SP EC’s stir up spider activity – they will draw spiders from their hidey holes and give a very rapid knockdown.  The solvent based EC’s will not be sucked into the non-porous painted timber surface, so will give some residual protection.    
On brick homes, EC’s will be sucked below the surface of the bricks, making them unavailable for residual protection.  WP, SC and CS formulations will remain available on the surface of the bricks, giving residual control of the spider’s food sources.  Spiders will shelter in the wall cavity behind weep holes, wall cavities should be treated with an electric dusting machine.

The SP EC’s will give spectacular results at the time of treatment but probably poorer residual – especially if your customer is expecting 12 months.  The perception of the performance of a spider treatment is judged by initial kill and reinfestation.  However some buildings are unlikely to be heavily reinfested, giving the appearance that a product is giving long residual when it is really a lack of reinfestation.

The flushing action of bifenthrin is promoted as being less than that of the other SPs.  This may be a disadvantage compared to permethrin EC’s where flushing from hidey holes is important in control.

Many pest managers that use Biflex for termite treatments have chosen to use Biflex for spider treatments through the same equipment.  They find this to be very convenient and most appear to be happy with the results.However, termite equipment is designed to deliver large volumes of emulsion at low pressure, whereas spider treatments are lower volumes at higher pressure requiring smaller diameter hoses and different nozzles.

Should you add a wetting agent - if so, what type?

There is a long held belief that a wetting agent should be added when treating spiders to allow easier penetration through the ‘skin’ of the spider.  This dates back to the days of the OCs and OPs and less advanced formulations.  Most of the products available now do not require addition of wetting agents for spider control.  If you choose to add a wetting agent, it is recommended not to add a vegetable based product as these will be ‘sticky’ on the building surface and attract dust, giving the building a dirty appearance.

When and how should the webs be removed?

When – there are three options – well before, at or after the treatment.
Before - if at least a fortnight before, allowing the spider to partially rebuild the webs is probably the optimum.  The house will be left with less webbing forced onto the building, however allowing a fortnight prior to treatment does not suit most pest management companies.
If the webs are removed immediately prior to treatment, the spiders will hide in the cracks and wall cavities at the time of treatment and be more difficult to control.

If the webs are left at the time of treatment, allowing good contact with the spiders, they may to be removed after the treatment.  The webs should be removed about a week after treatment to force the webless spiders to come into contact with residual chemical.  The webs should be brushed off rather than washed away to leave chemical on the surface.   

Spot treatment versus complete coverage

What is the expectation of your customer?  Are you giving a warranty?  A spot treatment will only dampen activity.  If you are giving a warranty (free service period), that implies a complete treatment.  If we get residual control by killing the food source, a spot treatment will not deliver any protection.

Warranty (free service period) and should it always be the same?

Some properties – urban areas surrounded by trees and lush gardens – are more prone to reinfestation than isolated properties.  There are often more hidey holes in a weatherboard house. Some chemicals have longer residual.  The arguments based on the pest, the product and the structure are endless but many pest managers disregard these and base their free service period on marketing – the opportunity to phone back in 12 months to ask for repeat business, but what happens if the treatment hasn’t lasted.  The dreaded recall, or worse, your customer has told their friends that your treatment hasn’t worked and they should not use you. 

When we 

• buy cars and electrical appliances 
• have the plumber or electrician install or service something 
• ask a pest manager to treat for termites 

the consumer expects to be free of problems for the stated warranty period or have a free service.  However, many pest management companies offer 12 months warranty on general pests then phone their customers prior to the expiry of the twelve months to retreat the property about the same time each year.  There will be an ever increasing number of ‘smart’ customers that will invite us back – at our cost under warranty.  The industry should consider giving a shorter free service period but with the recommendation of annual treatments, rather than 12 month warranties.  

This would satisfy the marketing reasons behind the ‘twelve month warranty’ and the reality of the length of residual of the treatment.
This is not a new concept outside our industry.  Dog wormers give instant kill of intestinal worms, with no residual but recommended three monthly retreatments.  The big difference is that we cannot see the worms in the gut of the dog, whereas our customer can see one or two spiders building webs on their pride and joy.