Spider spray does not last a set number of days. A knockdown spray kills the spider it hits and does little after that. A residual surface spray keeps working for longer, but how long depends on the label, the surface, sunlight, rain and cleaning. For pets and kids, the main rule is simple: keep them away until the spray is dry, and keep the can locked away.
Knockdown sprays and residual sprays
Knockdown sprays kill the spider you aim at, and kill it fast. Some use pyrethrins, a natural insecticide made from a kind of chrysanthemum flower. The Victorian Department of Health guide to pesticide classes says pyrethrins break down easily in air and light, so they do not stay active on a surface for long. The label tells you whether a can is a knockdown or a surface spray. Residual sprays are made to stay on a surface and kill spiders and insects that walk over it later. Common ones use synthetic pyrethroids, which are man-made versions of pyrethrins. The same guide says pyrethroids are more stable and stick tightly to materials such as wood and soil. It still rates them as usually low in persistence, so even a residual spray does not last forever. Redbacks that keep coming back under the back steps of a Birrong home a week after someone emptied a can on them were never touched by a lasting treatment, so book spider control in Birrong and have the steps and the gaps beside them treated where the spiders shelter.
What makes a residual spray wear off
The Victorian guide says sunlight and tiny living things such as bacteria break pyrethroids down. It also says pesticides can last longer indoors, because the sunlight, rain and soil microbes that speed up breakdown outside are missing there. So one spray can last different lengths of time on the same house.
- Sunny outside walls lose it faster, because sunlight breaks the chemical down.
- Garden beds and soil have microbes that break it down.
- Paths and walls in the rain lose it faster too.
- Indoor skirting boards and cornices stay out of sun and rain, so the residue can last longer.
- Surfaces you wipe or mop often lose some of it each time. Webs that return within weeks along a sun-baked garage door in Sefton are a sign the spray on that face has broken down, so ask for spider control in Sefton that focuses on the shaded edges and gaps where spiders actually hide. For an exact answer, read the label. Every pesticide sold in Australia is registered with the Australian Pesticides and Veterinary Medicines Authority (APVMA), and following the label directions is what keeps the product safe and effective. The Victorian guide says a technician should tell you the full name of the pesticide they used, so ask them how long it should work on your surfaces.
Is spider spray safe for pets?
Yes, if you follow the label and keep pets away until it dries. The NSW EPA advice on engaging a pest management technician tells householders to cover or remove bird cages and fish tanks, and to move other pets, before pesticides are used. Fish need the most care. The Victorian guide says pyrethroids are quite toxic to fish and other water animals, and warns users to take care near fish ponds and fish tanks. Cats and dogs should stay out of the treated area until it is dry, with their bowls covered or moved. Cats clean their paws by licking them, so a wet treated path is a quick way into a cat's mouth. A Villawood family with a fish tank in the lounge room and webs in the cornices should mention the tank when they book spider control in Villawood, so the room can be planned around it.
Is spider spray safe for kids and babies?
The NSW EPA says to leave the treatment area while the pesticide takes effect and to keep young children, pregnant women and older people away. Before anyone goes back in, the area should be dry and well aired. The Victorian guide gives "generally 4 to 6 hours" as the time to stay out until a spray is dry, but the label and your technician set the real time. It also suggests covering or removing toys, bedding, toothbrushes and food, and wiping benches and utensils before you cook again. In a Riverwood unit where a toddler crawls along the skirting boards, ask about timing when you book quick spider control in Riverwood, so the child can be out until the treated edges are dry. The can in the cupboard needs care too. Store sprays up high, in a locked cupboard, in their original containers. If a child swallows spray or gets it on their skin, the NSW Poisons Information Centre first aid advice is clear:
- Do not make them vomit, and give no food or drink until you have spoken to the centre.
- For spray on skin, take off wet clothes and flood the skin with cool running water.
- Take a photo of the label, then call 13 11 26.
- If the child is not breathing, start CPR and call 000.
When is the best time to spray for spiders?
The best time is just before spiders get busy. NSW Health guidance on snake and spider bites notes that spider bites happen more often in the warmer months, so late spring is a good time to deal with webs around doors, eaves and garages. Pick a dry spell, and clear old webs and clutter first.
Before you book
Note where you see spiders and webs, any pets, fish or young children, and when the house can be empty for a few hours. Send those details when you contact Bankstown pest control, and you will get pre-visit and post-visit steps to keep pets, kids and food areas safe.