I read on another forum that reducing the water PH to around a PH of 5 would increase the efficiency of pesticides and herbicides. Anyone doing this and if so do you really notice a difference?
Thanks Karl

it depends on the pesticide and the pest. For example, some eggs of codling moth will not hatch if there was dramatic change in pH of their environment (IIRC, will have to look it up) and has nothing to do with pesticide. The pH effect for example could also change the sex ratio like towards all males hatched. And of course, the pesticides themselves may be more toxic at lower pH, but it could lose potency too, depending on what type.

It is one of those things that you would need to know from the manufacturer or developer of the product as to the effectivity of their pesticide and possible effects by mixing it with others. Then if you can't find them, what were the experiences of others.

There are many possible interactions by adding pH reducer or increasing it. Copper fungicides will not be as effective if mixed together with some insecticides.

As Joe said-- it depends on the pesticide. Organophosphorus pesticides like Malathion are more stable under mild acid condition and hydrolize readily above pH 9. I do not know about the pyrethroids which are more common now, but in general they are more stable in either pH than the OPs.

Did the other forum actually say "pesticides and herbicides"? Pesticides is a broad term that includes herbicides, insecticides, fungicides, and rondenticides (and maybe something else I forgot).

Some commercial pesticides I use are put into water that I have first mixed a buffer into. I don't actually know what effects some of the materials I use have...I just follow the directions of the experts.

One thing I do know is that many folks waste Roundup by not first treating their water with something like ammonia sulfate (I use a liquid product because it is easier and still inexpensive). As I understand it, this isn't for the pH but, rather, that it binds with things such as clay and iron particles that would otherwise bind with the Roundup. Not all water needs to be treated but it is best to treat your water unless you've had your water previously tested for this purpose.

Harveyc
My mistake, they mentioned pestacides and fungacides only. Here is the link for the product.
http://rosemania.com/shopsite_sc/store/html/product40.html

They claim the product is the choice of expert growers but then do not use correct (expert) terminology. I imagine they mean "insecticides" when say "pesticides". The point I was making is that all of the classes are pesticices. Weeds, insects, fungi, and rodents are all pests and the chemicals we use to control them are all called pesticides.

The products label can be read at http://www.brandtconsolidated.com/clawel/pdf/Labels/Indicate5.pdf and describes the product as also treating hard water. It is used at the rate of 5-30 oz (or more) per 100 gallons depending on water hardness and it conveniently changes color to orange to indicate when the proper amount has been added. This may also make it easier for you to see the spray you are applying and aid in uniform coverage.

I have acquired 5 gallons of 75% Phosphoric acid that I use in hydroponics so if there is merit here it would not be much trouble to obtain superior performance by using a little acid One tsp in 5 gallons lowers my 7.3 PH water to 5.8. Anyway it seems like a cheap fix to get better protection or is it not worth the bother?
Karl

I believe it is well worth the bother.

Here are two sites that explain PH and Pesticide with tables to show the longevity of some pesticides at higher PH.
It’s interesting to see that Captan has a half life of 2 minutes at a PH of 9.

http://www.umass.edu/umext/floriculture/fact_sheets/greenhouse_management/ph_pesticides.htm

http://extension.missouri.edu/explore/agguides/pests/ipm1017.htm#tableone