Peter,
I'm not sure about what TOH is recommending but I would be cautious about their recommendations. Do a search at TR**buzz for " another TOH groaner". My original letter to them is there as well as others comments about TOH and arboriculture.
My preferred method of treatment is Merit soil injection. It is very effective and causes no damages like the injections do.
Mike,
I'm not sure about the quantities used in soil drenches but the injections with a Kioritz injector are only 1 oz per inch of DBH. If someone insisted on trunk injections for HWA, I feel imidacloprid will do just fine. I see no need to use a class B poison with a "danger" label when a "caution" label material will do the job. For those wondering, the ratings for labels are
"Danger" - most toxic (skull & cross bones included),
"Warning" - intermediate,
"Caution" - least toxic.
Besides, who wants all the extra PPE needed for Bidrin? Of course if your picture is in a magazine of a major TV program you can use shorts and short sleeves when doing Bidrin.
Paul,
Unless there is a new label in the last few months, there is no distance listed on the Merit label, just vague talk about being close to water and intertidal areas. If you call Bayer they will tell you not to apply directly to water and not in intertidal areas. You can go much closer but I will not say here, call Bayer for further information.
I'm not trying to criticize anyone, sorry if sounds that way, just trying to clarify some things.