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DESIGNING SUCCESSFUL SPIDER TREATMENTS

When it comes to spider control, success is achieved through designing an appropriate treatment and managing customer expectations. Understanding spider behaviour and preferred harbourages is key to success.

Generally speaking, spiders can be split into two behavioural groups – webbing spiders, such as redback and black house spiders, and running or hunting spiders, such as huntsman and white-tailed spiders. Control of webbing spiders is generally a straightforward treatment; providing protection from running spiders is more difficult.

Webbing spiders

Webbing spiders rely upon silk for their movement. Young spiders (or ‘spiderlings’) disperse by ‘ballooning’. They spin silk strands that are taken by the wind and then build their webs wherever they land, commonly against structures and stored items.

The black house spider (Badumna insignis) build its funnel-like webs around windows and door frames, under eaves and in other cracks and crevices. In their natural habitat they are typically found in the crevices of rough barked trees. The female rarely leaves her web and tends to become quite attached to a particular location. Males will wander in search of a female.

Carrying out a chemical treatment using EC (emulsifiable concentrate) or SC (suspension concentrate) formulations is a common method to control black house spiders. The most effective chemical management involves treatment that targets the spider directly in its harbourage, i.e. windows, doors, eaves, cracks and crevices, around the outside of buildings and along the fence line.

Chemical on the webs is not always an effective control means since most webbing spiders hang on using claw-like structures that do not readily absorb chemical residues. However, it is important to remind customers to wait two or three days before brushing down any unsightly webs – washing them down with water will obviously remove the insecticide and any possible residual performance.

SCs (suspension concentrates) are often preferred and used because they are likely to offer better residual value on porous surfaces typically found around a home, such as concrete, brickwork, pavers and timber. The use of this formulation type may also help reduce potential future spider ingress around the home by controlling the insects that the spider uses as a food source.

Likewise, the key for ensuring a successful treatment against redback spiders (Latrodectus hasseltii) is to treat the spider directly in its harbourages. In their natural habitat they will inhabit any dry, warm, sheltered position – typically in and around rocks and logs. Around buildings this means any cracks and crevices, roof voids (especially downlights), subfloors, outdoor furniture and fencing (particularly tubular pool fencing) are likely harbourages. The use of suspension concentrates and powders for roof and wall voids are the preferred control options.

Although golden orb and St Andrew’s cross spiders are ‘garden’ spiders and are viewed as ‘beneficials’ by many, for the arachnophobe they can be a big concern. Treating the spiders directly with a spray labelled for spider use will deal with the obvious spiders. Clearing back vegetation from the perimeter of the home and away from paths and driveways can help reduce any incoming spiders building webs in the obvious positions likely to cause the homeowner concern.

For garden spiders, such as the golden orb weaver, direct spray and clearing back vegetarian is the best strategy
With the black house spider it is important to target the spider not just the web

Running spiders

A simple barrier spray, even a comprehensive perimeter treatment (complete external wall area, one metre out, and all entry points), is unlikely to provide protection from running spiders. This is because spiders such as huntsman and white-tailed spiders tend to walk on the tips of their legs and pick up a minimal amount of insecticide.

Offering a service free period for any spider control can be difficult, but to include running spiders would be risky as their behaviour and movement means homes are always likely to get the occasional invader, no matter what treatment has been applied. However, the combination of a general pest spray plus targeted treatment can significantly reduce the chances of such spiders entering the home. A general pest treatment or a treatment for webbing spiders will reduce the number of prey insects around the home, making it less attractive for hunting spiders. Indeed, the black house spider is one of the preferred prey items for the white-tailed spider. Coupled with removing/trimming back vegetation from the building perimeter, this can be very effective.

White-tailed spiders (Lampona cylindrata and Lampona murina), live beneath bark and rocks, coming out at night to hunt. Their preference for resting in tight spaces means they like the folds of clothes left on the floor and bed sheets. Huntsman spiders (there are a variety of different species) tend to inhabit similar locations to white-tailed spiders.

To back up the external treatment, for those customers experiencing a significant problem, internal treatment of cracks and crevices and powder treatment for roof and wall voids should also be considered.

For customers experiencing problems with other spider species, the treatment can be modified once the species has been identified and their behaviour and preferred harbourages understood.

Brett Black, Globe Branch Manager, Padstow, NSW

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