As experienced pest managers we probably all agree that spider management is nowhere near as challenging as the likes of bedbug management, ant management, German cockroach management and especially termite management. So when we do get that occasional call back on a spider treatment that we have done, it is usually unexpected and outright annoying. And it quite often involves a full respray which costs us in many ways. The primary question we ask ourselves when this happens is WHY?
Spiders are extremely variable in morphology and in behaviour. Obviously then, different treatment methods are going to be more effective than others against different types of spiders. It puzzles me that we place so much emphasis on identification first when it comes to ants, cockroaches and termites before we formulate a management plan, yet rarely are we encouraged to identify spiders before treating. Even many of our product labels differentiate between different ant species, cockroach species and termite species yet lump all spiders under the one heading “spiders” or in a few cases “webbing spiders” and “non- webbing spiders”. The issue is that there is such an enormous diversity of spiders that it would be impractical to list each species as we do for other pests. It is perhaps more realistic to learn about the spider groups that we are most likely to encounter as part of urban spider management. Spiders can be divided up into two main groups Mygalomorphs (primitive spiders) and Araneomorphs (modern spiders).
Mygalomorphs have parallel fangs and require a downward strike to stab their prey. They also have a basic respiratory system called book lungs which are prone to drying out, hence favouring moist habitats or burrows to retain moisture. This group of spiders includes Trapdoor, Funnel-web, and Mouse spiders.
Aranaemorphs have opposing fangs, enabling them to “pinch” their prey. Their respiratory system is more advanced with a tracheal breathing system as well as a single pair of book lungs, enabling them to live in basically any habitat. This group of spiders includes Redback, Wolf, Huntsman and Orb Weaving spiders.
Araneamorphs can be further broken down into the following groups based on their method of prey capture.
Open range hunters- includes Wolf, White-tailed and Huntsman spiders.
Ambushers and Anglers- includes Crab, Net-casting and Bird-dung spiders.
Apprentice Weavers- includes Redback, Black House, and Daddy Longlegs spiders.
Master Weavers- Includes St Andrews Cross, Garden and Golden Orb spiders.
The following is a brief outline of most of our common spiders and their biology and how to best target these spiders. And thus ultimately reduce those annoying call-backs.
Wolf spiders – Lycosa sp.
There is currently more than 100 described species of Wolf spider, however, it has been suggested by many that there is really more than 1000 different species. Wolf spiders are easily identified by their eye arrangement having two prominent eyes above a row of 4 smaller eyes, with two small eyes set laterally behind the prominent eyes. This spider also has the unique habit of carrying its young around on its back. The most commonly encountered of these is the Garden Wolf spider Lycosa godeffroyi. This spider has been implicated to potentially cause necrosis. Wolf spiders are classed as open range hunters and are extremely common in open farmland areas where by day they hide in shallow burrows and by night wander significant distances in search of prey. Wolf spiders lack claw tufts thus cannot climb smooth surfaces.
Treatment: The key to the successful treatment of wolf spiders is creating a broad horizontal residual treated zone, particularly around porch areas where they are often attracted to by flying insects drawn to the lights. Pay special attention to garage entries and other doorways where these “SCARY” spiders will often find their way inside. The wider the horizontal treated zone the better. If large areas of porous surfaces such as concrete are required to be treated a suspension concentrate is considered to give a quicker knockdown with its larger particle size.
Redback Spider – Lactrodectus hasselti
The Redback’s reputation is unparalleled yet there has not been a recorded death since 1956 which incidentally was the year that a successful antivenom was produced. The Redback spider is considered to be the same species as New Zealand’s Katipo and America’s Black Widow spider. These spiders are extremely prolific. Potentially reaching maturity within 6 months and producing 6-8 egg sacs with up to 300 young in each sac. Without predation, Redback spider numbers can explode in a relatively short time. Redback spiders are referred to as gum footed tangle web spiders, meaning they tend to hide beneath things and construct sticky strands of web radiating down to the ground. Many similar shaped spiders are incorrectly identified as Redback spiders or especially male Redback spiders. The female Redback spider is easily identified by an hourglass-shaped red stripe on the ventral side of the spider, whereas the male is significantly smaller and white and brown in colour.
Treatment: The key to successful treatment of Red-back spiders is getting the product up under the objects where they are hiding. A space spray, fog, or mist can be easier to deliver to these areas than a coarse spray.
White-Tailed Spider – Lampona sp.
This spider’s reputation is great for pest control business; nothing prompts a phone call from a homeowner to their local pest control company more than the sighting of a White-Tailed spider.
Unfortunately for this spider, its reputation is probably unjustified according to the following paper.
Isbister, G.K. and Gray, M.R. 2003. White-tail spider bite: a prospective study of 130 definite bites by Lampona species. Medical Journal of Australia 179, 199-202.
White-Tailed spiders are nocturnal hiding in dark voids during the day then actively wandering around within our homes looking for prey, particularly other spiders.
Treatment: The key to successful treatment of White-Tailed spiders is the treatment of their frequented areas, residual surface sprays of skirting areas and a thorough dusting of roof and wall voids.
This spider is an arachnophobes worst nightmare, big, hairy and they love the shelter that our homes provide. Huntsman spiders are perfectly adapted to living in tight crevices such as the loose bark of trees and the timber weatherboards of our homes. Huntsman spiders are distinguished from other spiders by having two rows of four small eyes, rear pointing elbows and excellent climbing ability. Huntsman spiders are generally considered harmless, except for members of the genus Neosparassus (Badge Huntsman).
Treatment: The key to the successful treatment of huntsman spiders is to focus on vertical surfaces internally and externally. These are large hairy spiders that take some stopping, so once again a suspension concentrate formulation can have a quicker knockdown.
Black House spiders – Badumna sp.
This extremely common spider makes itself at home in virtually every household. Often referred to as Window spiders it is also sometimes incorrectly called a Funnel-web spider due to the funnel-shaped web it makes in any available nook or cranny. These spiders have also been implicated as possibly causing necrosis from a bite, yet don’t receive the hysteria normally associated with White-Tailed spiders. This is most likely due to a Black House spider’s habit of not leaving its retreat and wandering around the house like that of White-Tailed spiders.
Treatment: The key to successful treatment of Black House spiders is thoroughness, treatment of every accessible crack and crevice, focussing on the door and window frames, downpipes, veranda attachments, weep holes, the list is endless, but basically anywhere you see webbing. A long residual isn’t as critical as these spiders vary rarely leave their web.
Funnel-web and Trapdoor Spiders
These spiders can occur in large numbers in suitable habitats. As females reproduce the young leave their mothers to burrow only to walk a short distance to start a new burrow. They normally favour moist shady areas of the lawn or garden. Spiders normally don’t leave their burrow unless disturbed or during the warmer months of the year when mature males go in search of females. Not all Trapdoor spiders have a trapdoor on their burrow. Although the Sydney Funnel-web is well known, Funnel-webs actually occurs along the entire east coast of Australia. There have been no recorded deaths since 1981.
Treatment: The key to successful treatment of these spiders is the treatment of suitable habitat for them particularly if burrows can be located, then using a broad, residual surface spray over these areas. Avoid using repellent chemicals as this will drive them out of their burrows rather than killing them in situ.
Personally, I don’t see the point, however many customers request it. All orb-weaving spiders including Garden and Golden Orbs, St Andrews Cross spiders are considered harmless. These spiders utilise structures and vegetation around our homes to construct their wheel-shaped webs to catch the bountiful insects drawn to our houses and gardens.
Treatment: The key to the successful treatment of orb-weaving spiders is getting a very fine spray to drift through and around surrounding vegetation and structure used for web construction. A knapsack misting unit is perfect for this task.
Assessing the site
As with any pest treatment, a spider treatment should always begin with an inspection. By no means am I suggesting a two-hour inspection like a termite inspection, but simply a quick assessment that begins as we arrive at the site. What kind of environment is it? If it’s open farmland then Wolf spiders and webbing spiders are likely to be a problem. If it’s woodland then Huntsman spiders might be an issue. A quick lap around the house will also identify problem areas and finally and most importantly ask the client. What spiders is she concerned with and where? No point in treating her gardens for orb-weaving spiders when it’s big hairy spiders like Huntsman spiders in her house that she is concerned about.
We as humans create an environment perfectly suited for many spider species, we build a structure for them to build their webs on or seek refuge and we then turn our lights on to lure in every flying insect straight to their laps. Many of these spiders would never reach the population densities that occur around our house, in a natural undisturbed environment. It’s our role as pest managers to restore this balance; using the resources we have available to us including our brains!!
It is agreed that a typical spider treatment will manage most spider species but a targeted treatment will yield better results and hopefully eliminate that annoying callback.