Robert's Rants
Robert's Rants
A personal blog on the Canadian pesticide industry and other pet peeves and interests

Call backs this Summer – Pyrethroid Performance

I am starting to get a few calls and questions on call backs and retreats needing to be done in some areas around the country.  Seems to be more spider related than anything.

There are three separate issues that need to be addressed with this;

The limited chemistry we have available,

The inherent physical properties of these chemistries,

And lastly the year we have been having weatherwise.

When you look at it, the only three products we have for outdoor structure and perimeter control are Demand CS, Prelude and Dragnet.  All three are good products, but every one is a pyrethroid.  That’s a sad reality we have to work with (PMRA, if you are reading this please approve a few more chemistries like chlorfenapyr!)

Part of the inherent properties of pyrethroids is they break down more rapidly with UV exposure, high heat and humidity.  This is especially true when not in contact with organic matter where they are heavily bound.

So this summer what are we seeing?  In many places high temps, high humidity and lots of sunshine.  This simply means we will be seeing a faster breakdown of the pyrethroid molecule and a greatly reduced residual activity.  Especially since the area of application is on houses, and not high levels of organic matter.

I think the perimeter apps on soil around structures are still holding for ant control, especially with the microcap Demand, but spiders are the problem.

Plus this weather is just what spiders love, so you are going to see heavy populations.

Unfortunately, a re-treat may be called for.

If you need more help, you know where to find me!