North American Fruit Explorers mailing list at ibiblio

[Steve <sdw12986@aol.com>]

Thanks for the explanation, that makes sense. I have about 2 miles of 
water directly west of my yard then miles of native forest beyond that. 
I figure the number of disease spores drifting into my yard is less than 
the average person's yard (perhaps with neglected apple trees just 
upwind). If I can keep things under control in my own yard, I should be 
in good shape. This is the kind of information I signed onto this group 
for. I should have done it years ago!

Steve

Mark & Helen Angermayer wrote:
> Hi Steve,
>
> My experience with apple scab is mostly from reading, but what you describe
> seems to match up quite well with the literature.  Scab infections start
> with "primary" infections that result from last years leaf litter, fruit
> drops, and infected twigs.  The scab fungus waits till the spring to release
> the primary spores.  Interestingly, the fungus waits till a good wet period
> to release its spores, then it's pretty much done.  In other words, the leaf
> litter is like a roman candle.  Once it's shot, it's done.  So if you can
> protect your apples from the primary infection (if I recall from the period
> from tight cluster to first cover) then there is no more inoculum left to
> infect your apples.  However, if the current season's crop gets infected,
> the infected apples on the tree will continue to release spores all summer
> long and it becomes a constant battle to keep scab from spreading.  It also
> means you'll have more primary inoculum for next year.  So your early
> fungicide treatments probably were protecting you from scab in past years.
>
> No idea why Manzate has such a lengthy withdrawal time.  As you suggest, it
> doesn't have any systemic action and is considered a protectant fungicide
> with about 24 hours kickback activity.  Maybe it's a real 'sticky' fungicide
> that just takes a long time to wash all the residue off.
>
> Mark
> KS
> ----- Original Message ----- 
> From: "Steve" <>
> To: "NAFEx" <nafex@lists.ibiblio.org>
> Sent: Tuesday, July 15, 2008 10:28 PM
> Subject: [NAFEX] Apple Fungicide
>
>
>   
> > We had a stretch of damp weather and I have quite a bit of scab on my
> > apples this year. I had nice crops of apples the last 2 seasons with
> > absolutely no scab. What was the difference? Maybe it was the weather
> > but maybe not:
> >
> > Three or four years ago, I bought some Manzate. I actually bought it
> > with my other hobby in mind; I wanted to cure some problems on my orchid
> > plants that I assumed were fungal in nature. That didn't work out as I
> > hoped, so I read the label to see what fruit or garden plants I could
> > use it on. Pome fruits were listed so I used it on my apple trees. It
> > was labeled for use no later than 77 days before harvest. (I couldn't
> > help but wonder how they arrived at that exact number of days.) The last
> > 2 seasons, I did two sprays (I think, ... it may have been only one
> > spray last year) before and/or toward the end of bloom. (My earliest
> > apples probably were ready in slightly less than 77 days after the last
> > spray.)
> >
> > As I said, my apples were completely clean those 2 years. This year I
> > didn't use the Manzate and, even though I plucked off the worst of them
> > at my last thinning, I'm going to have a lot of blemished apples. This
> > is the only fungicide I have ever used on my apple trees. My question
> > is, is the Manzate so effective that it prevented scab right through the
> > entire season with no more than 2 early sprays, or was it really the
> > weather that made all the difference?
> >
> > One other thing. I wondered if Manzate was somewhat systemic and that
> > was the reason for the long 77 day requirement before harvest. This site
> > was shown by someone here a month or 2 ago:
> > http://www.ipm.osu.edu/fruit/03icm31.htm\
> > The third section down discusses the effects of rain on fungicides. Some
> > are listed as penetrating the leaves and fruit tissues and don't wash
> > off. Manzate is in the group that does wash off in the rain, making me
> > wonder why the 77 day preharvest requirement and making me seriously
> > question if the Manzate was really what saved my apples the last 2 years.
> >
> > Steve in the Adirondacks (Zone 4 on the map, zone 3 by the thermometer.)
> > _______________________________________________
> >