Spider Control – A technical Review

When dealing with spiders, it is important to remember that they aren’t insects, but arachnids. Insecticides don’t affect them in the same way that insects are traditionally affected, except by contact spray. Most bugs you spray directly with a pesticide will die.

What I mean by insects being traditionally affected is this: when an insect walks across a dried residue of a pesticide product like…say, Talstar P, it gets the product on the ends of it’s legs. Insects groom themselves, and in doing so, they ingest the product and die. Well, spiders aren’t insects, and they don’t groom themselves. So…what do you do? Microencapsulated concentrates!

Microencapsulated pesticides use science to place tiny, microscopic droplets of the active ingredient inside little polymer shells. You apply the product in the same way you would any other pesticide used for structural pest control; following label directions of course, but you get the drift. When the product dries, it’s like microscopic bubble wrap. As spider’s walk across this barrier, they accumulate some of these microcapsules on their legs, which eventually rupture, killing the spider on contact! How cool is that?   

Two of the big dogs in microencapsulated concentrates are Syngenta, which makes Demand CS, and MGK, which makes Onslaught. Both are absolutely fantastic for spider control. My personal favorite is Demand CS, but only because I’ve been using it so long with success. Onslaught is definitely the newer of the two, but no less effective. Active ingredients differ between the two products. Demand CS comes in either an 8-ounce bottle, or a quart. It contains 9.7% Lambda-cyhalothrin. It can be mixed in several ratios, but when dealing with a heavy infestation, you want to mix it at the highest labeled rate, which is .06% you achieve this by mixing 0.8 ounces, or 24ml of product per gallon of water. After you have the infestation under control, you can use the lower rates of .015% or .03%, to maintain a bug free structure. Typical applications are spaced every 30-90 days apart, but can be done as often as every 21 days, to maintain control of the pest. When applying, you want to pay special attention to the areas where they may enter the structure, such as weep holes, window and doorframes, siding joints, eaves and overhangs, as well as any crack or crevice. Apply on the inside as a crack and crevice and/or spot treatment. Spots are usually considered 2 square feet. It may also be beneficial with a heavy infestation to dust the attic with a product like Tempo 1% dust. This can be applied with a standard bellows duster, or pump duster.

This dust will kill any spiders on contact, and because walking through the settled dust gets on the spiders’ bodies, contact kill can be achieved residually. Tempo will last up to one year. Onslaught has a slight odor, but not one that overpowers the applicator. Remember when applying any pesticide, it is necessary to read the label fully from front to back before use, to determine the recommended personal protective equipment which may or may not be necessary to don before application. Onslaught also has a much broader label, as concerning controlled pests (over 200!), although Demand is no slouch where covered pests are concerned. Onslaught contains 6.4% of an active ingredient with no common name. It’s called (S)-cyano(3-phenoxyphenyl)methyl-(S)-4-chloro-alpha-(1-methylethyl)benzenacetate. What a mouthful! It’s mixed at a rate of .5 oz. Per gallon for a .025% mixture, or 1 oz. Per gallon for a .05% mixture for heavy infestations. It’s applied just like Demand for spider control, but refer to the label for more detailed instructions. It’s available in a pint.


Disturbing feeding areas also work well as another tool in your arsenal to achieve maximum control. I recommend using a web broom to knock down cobwebs. After that’s done, use some Cobweb Eliminator to keep them from being able to put the webs back!

Hopefully this article was helpful. Our website has all of the products talked about today. Please refer to the index, and search for them today! Happy Hunting!