Ask the Expert - Spiders

Not insects at all but a true pest to so many people, Spiders are probably the number one reason for calls during the busy pest season. They cause considerable discomfort to so many homeowners. For many, the thought of them sends shivers down the spine and it’s the one pest most people cannot stand sharing their environment with.

Print page spider control - Bayer
Spiders can generate powerful emotions that are disproportionate to the threat they present. Strong reactions motivate customers to look for a spider control service. This can be lucrative work if you know what you are doing but problems can arise if you don’t pay attention to the basics. 

Knowing the pest and its habits are critical but so is choosing the correct formulation and application.

Finding the right treatment
Not all spiders treatments are the same. The most common spider treatment is for webbing spiders. All spiders produce silk but this group builds extensive prey capturing webs, causing problems inside homes, on outside walls, around lighting and even through gardens and pathways.

Effective treatment requires specialized application equipment. Webbing spiders such as the Daddy Long Legs (Pholcus phalangiodes) are found in every window frame, curtain rail, cornice area, furniture hollows etc... Very fine application techniques are essential to treat these areas and to prevent off-target issues such as run-offs from over application.

Spiders establish themselves close to an escape area into a void. For effective control, you must treat the voids directly. The most important formulation in spider control is a dust such as Coopex. You can’t rely on the residual nature of a spray because there’s no guarantee spiders will make contact with the active.

Externally, conditions are different but the general principles still apply. Firstly, apply dust to all voids and cavities in walls, eaves, framing etc., eliminating the spider’s refuge.

Application to outside surfaces should be performed using power gear and a correctly calibrated spray tip. Your treatment rate is 1L/20 m2 so your nozzle needs to apply a very fine spray. The critical treatment points to pay attention to are:
  • Avoid run-off
  • Avoid non target areas e.g. windows
  • Avoid drift
  • Ensure complete coverage. 
  • Areas that do not receive correct application quickly become reinfested.

External webbing spiders such as Red Backs (Latrodectus hasselti) are responsible for agonising bites to humans and nest in nooks such as bin handles, chairs, BBQ’s, letter boxes, etc. When treating, invert all outdoor furniture to expose the underside where spiders hide during the day.

You should also inspect and treat hollows in retaining walls or other garden sculptures. A backpack mister is the ultimate application tool for gardens, sheds, debris, stored items, fences, trailers, etc. The airflow created carries the insecticide directly to the webbing and even to the spiders.

The Importance of residual treatments
Webbing spiders move by a process known as ballooning. Young spiders secrete a silk strand into the air on a prevailing breeze and are picked up and carried by the wind until they hit a solid surface. With a residual chemical in place, these spiderlings are killed preventing or suppressing recolonization while the residual lasts.

Another interesting benefit of residual treatment is its effect on other insects that inhabit the area. These insects are a food source for spiders, by reducing them, it can also supress the spider population.

Non Webbing Spiders
Non-webbing spiders have completely different habits and are very difficult to control. A lack of webbing makes them tricky to locate. Typical pests from this group include the Huntsman spider (Isopoda & Helconia sp) and the Wolf Spider (Lycosa sp.) These spiders hunt for prey (usually small insects) in cracks and voids or across open ground.

Dusting is essential for treating voids while internal misting always pushes spiders out of their harbourages. Huntsmen love to rest around curtains and above the rails.

External residual treatments are an important element of your control program but there are limitations. Wolf Spiders nest in soil burrows so include a ground spray to about 5m out from the structure. Cavities are found in debris, mulch, retaining walls, paving, pot-plants, and rockeries - any area where stacked items create insect harbourage.

Treating dangerous species
When treating primitive spiders (Mygalomorphs) be very thorough and also quite careful to avoid becoming a victim of these dangerous pests.

Funnel webs (Atrax & Hadronyche sp.) are difficult to locate without very careful inspection of garden areas. These ground dwelling spiders rarely come in to contact with humans, only when digging into the ground. Unfortunately, the male spiders can roam during the mating season and wander into areas where they are a danger.

Spiders are part of Australian life
Customers should be encouraged to accept spiders as a normal part of living in Australia, they are important to the natural ecology. Educate them about best practice around spiders. They are dangerous so it is important that steps are taken to protect the people involved.

A word of warning about spiders in a swimming pool, they can live for an amazingly long time under water. If you find a spider curled up on the bottom of the pool, don’t assume it is dead. You may find yourself in a very painful situation.

What chemicals should be used?


Firstly, you need a dust, preferably, a permethrin-based dust such as Coopex Insecticidal Dusting Powder. Dust has a fantastic ability to drift large distances into voids and attaches to spiders webbing, in particular the sticky strands. Dust is a powerful tool in spider control.

For a spray, it has to be Cislin 25, the leading insecticide in Australia for over 25 years. It is ideally suited to residual spider treatment and provides unparalleled control due to its highly efficacious properties and its ability to provide long residual action.

Sensitive domestic treatments
When treating a major infestation of webbing spiders inside a home, Perigen Defence is a good option, misting operations are far more effective. It’s also a great deal safer than other products. Airborne deltamethrin is a considerable risk until the active has settled, so using Perigen for misting where the active ingredient is likely to be airborne for long periods is a much safer approach to control.

Non-repellent treatments for dangerous spiders
For ground dwelling spiders that you don’t want to aggravate, choose Baytex 550 or Ficam W to prevent flushing out dangerous spiders. These non-repellent chemicals kill the spiders slowly and they die in their burrows.

Good hunting!