A guide to the spiders pest managers will most commonly encounter on the job.
More often than not, spiders are not a difficult pest to control – a general pest treatment or “spider spray” will deal with most spider problems, especially web-building spiders. But every now and then, customers have a significant spider problem. In such cases, pest managers need to do a bit more thinking. A successful treatment will come down to the pre-treatment inspection and uncovering the origins of the infestation. Essentially asking, where are the spiders coming from?
To work out where spiders may be hiding, it helps to know where they typically live in their natural habitat, as they will try and find similar hiding places in and around buildings. Here is some information on the living habits of the common spiders found around Australian homes.
Web-building spiders, such as black house spiders and redbacks, aren’t normally difficult to spot – their webs are a big giveaway! Black house spiders with their dense funnel-shaped webs are particularly easy to spot. Normally they would live in crevices on trees, under and around logs and rocks. Around homes they can be spotted around window and door frames, eaves, under outdoor furniture and barbecues, and in post boxes and electrical boxes. Like their natural habitat, they can also be found around wood piles, but also amongst stored belongings both outside and in the subfloor. It’s also important not to forget fencing, especially inside metal tubular fencing around pools. Redback spiders, which can tolerate quite warm, dry environments, can also be found in roof voids, particularly around downlights, where they can easily catch insects.
The hiding places of hunting spiders are a bit more of a challenge to locate, as they do not produce obvious webs and when they do, they are often only transient in nature. Two species of hunting spiders that are commonly found inside and will happily set up home in and around buildings are the white-tail spider and huntsman spiders.
In the natural environment, white-tailed spiders live underneath bark and rocks or in the leaf litter – they like to squeeze into tight spots, which is why they are quite often found between clothes left on the floor or between bed sheets. Typically, these are only temporary resting places. If there is a white-tailed spider infestation, it is likely there is a large population outside the home, or one or more female spiders have set up a temporary home inside to lay their eggs. They will choose a temporary retreat, which they line with silk to lay an egg sac, which can contain up to 90 eggs. Such hiding places can be behind cupboards and in wall voids, and particularly behind weatherboards in older homes. Spaces between stored items around and under the home should also be considered likely hiding spots.
Huntsman spiders will live in much the same places as white-tailed spiders, their flattened bodies allowing them to squeeze into a variety of tight spaces. This often allows individual spiders to gain access to unwanted areas, for example squeezing under the back door or around the car door! Much like the white-tailed spider, huntsmans only generally come inside when looking for food or to escape the heat. However, the females of some species can come inside looking for a place to lay their eggs. In such cases, she will find a suitable crack or crevice, for example behind a cupboard or toilet cistern, where she will create a silken lair that includes her egg sac, which she will guard until they are ready to hatch. The females of other species will carry their egg sac but may be inside when they hatch. As huntsman spider egg sacs contain up to 200 eggs, when these hatch and the spiderlings burst out, you can have an instant infestation!
Generally speaking, for hunting spiders to be found inside the home means there must be favourable conditions outside the home for a significant population to build up. In many cases this will mean the home may be in a bush-like setting or have dense vegetation around the perimeter of the building. There’s not much that can be done about a bush setting, but keeping the perimeter of the home clear of vegetation and leaf litter will make a big difference, not only reducing spiders and other pests, but making termite management easier too. A regular perimeter spray will also be beneficial in dealing with hunting spiders, as it will eliminate a wide range of insect pests and web-building spiders, all of which are prey for hunting spiders. If there’s not much food around, hunting spiders are likely to move elsewhere.
Funnel-web spiders tend to build their burrows in moist, cool, sheltered locations, and also under rocks and logs. They are found along the east coast of Australia and in Tasmania. If a funnel-web is found wandering in or around a home, it will almost definitely be a male. They go wandering from November to April, leaving their burrows to look for a mate. If you do find a wandering funnel-web, it does mean there are likely to be funnel-web burrows nearby (although they can wander up to 60 metres in a night). So, if your customer has concerns, you should take time to inspect the yard and surrounding area. Where there is one burrow, there is generally more – they are not territorial and there can be a high density of burrows. Treatment for funnel webs requires the burrows to be located and treated directly.