Bryan Davis and I have been working with a grower in Ashe County who treated multiple fields in 2009 with Dimethoate + Asana using a high pressure spraying for scale, starting June 26th and going all the way through September 7. Most of these fields had a very heavy incidence of scale.
What we're finding so far is that the fields treated in June and July and into the first 2 weeks of August had decent control -- mostly 90% or better. By later in August and into September, control really dropped off -- to about 70%.
Of the 8 or so fields we've looked at so far, all appear to have twig aphid control and only one had a heavy incidence of hemlock rust mites. The grower didn't use any Envidor. In the bigger sized trees, we'll go back and check on twig aphid control again, but hopefully it will be sufficient. In one spot where there had been balsam woolly adelgid, it had also been controlled.
At a meeting I had last night in Watauga County (which is sort of EHS central!), a grower shared that in a block of trees where he's had to treat for rosette bud mite, spraying Dimethoate by itself in June, he's had no EHS, even though there is plenty of scale all around him.
So, should we even be treating earlier for EHS? In June perhaps?
ALERT: Also wanted to let everyone know that a new scale which they are having problems with up north in Frasers and other firs -- Cryptomeria scale -- was identified last week in Macon County. It was the first reported incidence in North Carolina.
Scales are definitely becoming more of a problem. Is it the loss of Lindane? Warmer winters? More use of synthetic pyrethroids and Thionex? One thing's for sure, they will make international marketing a lot tougher, as the presence of most of these scales will stop sales.
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