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.)