Sep 3, 2012 – Death to Black Widows

QUESTION:

What is the best pesticide for killing black widows?

ANSWER:

Based on their history of success I think that the synthetic pyrethroids still are excellent products for spiders of all kinds. We do have to keep in mind, though, the new labeling on all pyrethroid products and how this may affect our application. There are now restrictions on how much of the exterior surface of a structure can be treated, and this now allows only "spot" applications above that 3 feet above grade level. Since a spot is an area no larger than 2 square feet, as defined by EPA, the use of a power sprayer to treat for spiders may not be the most manageable way to apply the products. The new labeling does not further restrict applications to turf and ornamentals, so if the spider problem happens to be on and within shrubbery in the landscape then there are no changes. And, it appears that treatments to the "undersides of the eaves" also fall into the "exceptions" the EPA put into place and that treatment to this area is not restricted to spot application. 

Prior to the introduction of pyrethroids for our industry we had some tough times killing certain spiders, and in particular this was the cellar spiders (a.k.a. "daddy long legs spider") that make so many messy webs under the eaves and around windows. When cypermethrin was first used it seemed to resolve all these difficulties and spider management took a nice turn for the better. I still hope, however, that many customers can develop a tolerance and appreciation for many kinds of spiders that do not make messy webbing and which are not dangerous. This includes wolf spiders, ground spiders, and the fascinating jumping spiders. Given that all spiders are feasting on other kinds of bugs, having them around would seem to provide a benefit. 

The news media recently has headlined, in California at least, the appearance of the Brown Widow - Latrodectus geometricus - and since the best news headlines are the scary ones they also have "suggested" that the venom of this species "may" be more toxic than that of the black varieties. For decades this species has been present in Florida, but in 2000 began to show up in other surrounding states and in 2003 showed up in southern California. Now, there's nothing we folks in California like better than a good spider scare, so the media have accepted the brown widow with open arms. However, experts at U.C. Riverside tell us that the venom itself appears to be no more or less potent than the venom of black varieties and that the Brown Widow appears to be unable to inject as much venom with a bite, so the overall effect on people is less. 

The web of black widows is usually easy to distinguish. It is a haphazard pattern and not the neat geometric design of orb weavers. It is sticky and extremely tough, so that passing a stick through the web results in an actual audible "snap" as you break the strands. The spider itself will often be hiding nearby in some cozy crevice, so treating the surfaces around the web will be necessary. It also is handy to remove all the webbing so that you can tell if the job is successful. If new webs are built shortly after your treatment then the spiders somehow survived. 

Black widows are one group that disseminate by "ballooning". The very young nymphs release strands of silk into the breeze and then let go of the surface, allowing the wind to transport them to wherever it will, sometimes well up on buildings. The widow spiders are very clumsy on the ground and are far less likely to walk to a structure than to fly to it. This makes prevention more difficult but helps your customers to understand why they keep getting the darned things. 


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