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nafex - Re: [NAFEX] Compatability of sulphur and BT (Bacillus thuragiensis)

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  • From: Ginda Fisher <list@ginda.us>
  • To: North American Fruit Explorers <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] Compatability of sulphur and BT (Bacillus thuragiensis)
  • Date: Thu, 22 May 2008 13:44:35 -0400

It sounds like you have the same problem with winter moths that I have -
those are the abundant, predator-free caterpllars who crawl into buds as soon
as the scales loosen and preferentially eat out the flowers-to-be. The long
term outlook on winter moths isn't too grim as various agencies are breeding
and releasing a predator from wherever they come from, but at the moment
there are pockets with phenonimal levels of infestation. I had about one
caterpillar per 3-5 fruiting apple buds this year (having treated the last
two years) but a nearby park was measured at 10 caterpillars per oak bud! My
sister had four fruit trees that were 100% defoliated by them last spring.
(the second flush of leaves survived, as the caterpillar's active life cycle
is very short - nearly over here in eastern Massachusetts.)

The caterpillar stage is a very small 'inchworm'. The moths emerge in
November or December to breed and lay eggs in the ground. They are very
noticible around light on early winter evenings if you have a lot of them.
U-Mass extension has a lot of good information on them.

My research suggests that spinosad is much more effective against winter moth
than is BT, and it's only slightly more toxic to beneficials. You can buy
formulations of spinosad that are labelled 'organic'. (At least, the tree
guys I hired to spray my oaks claimed that stuff they were using was
certified organic by some reputable registry, maybe OMRI.)

I've hired professionals for my oaks, but I monitor and treat my fruit trees
myself. When the weather begins to get warm and the apple buds begin to
swell I look at several buds closely every evening. At the first sign of
damage I assume the caterpillars have emerged and spray. Careful inspection
usually shows dead caterpillars the next day - they are tiny, I posted a
photo a year or two ago, maybe 1/16th of an inch long when they hatch. (the
tree guys I hired gave the same hatch-date that I did this year.) I then try
to spray about once every week or two until the flowers open, when I stop.
(that's two or three sprays.)

I just have a couple of young trees, and I can spray them in under an hour,
counting changing my clothes twice.

I have no idea if spinosad is compatible with sulfer. It's not alive, so
maybe?? Your local ag extension might be able to help you with that.
___
Ginda

..... Original Message .......
On Thu, 22 May 2008 12:42:58 -0300 David.Maxwell@dal.ca wrote:
>Most interesting issue.  I am more-or-less organic, currently using wettable
>sulphur for control of scab (I need it - we live on the Atlantic coast, and
>it is wet.) I also have a major problem with the spring caterpillar complex,
>who get into the flower clusters even before the blossoms open.  To combat
>these I want to spray BTK.  The question is whether this is even possible. 
>I supect that tank mixing is completely out, as the sulphur will change the
>pH and kill the living bacilli.  How about spraying sulphur one day, and BT
>the next day?  The sulphur will still be sitting around on the leaves - will
>it kill the BT?  Obviously I can't wait until all the sulphur has washed off
>with the next rain before spraying the BT.  Can the two coexist at least on
>the trees? If so, how long between the sulphur and the BT do I need to leave?
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