The problem is probably with the last two fungicide applications,
captan and Scala. These materials are not very effective against rust,
and if you had a bad rust year, they probably didn't do the job. A bad
rust year happens when you have frequent wetting during the time that
galls on cedar trees are releasing spores, from early tight cluster
through early fruit set. In addition, the other part of the disease
cycle involves infections on cedars in late summer and early fall, and
if you had a lot of wet weather during that period in 2007, it may
have produced a lot of infections on cedars that became inoculum
available to infect apples in 2008.
Since you've never had a problem before, I expect that there was an
unusually high amount of inoculum last year, and the two final sprays
of captan, then Scala, didn't do much to control it. Another
explanation might be that in previous years, you've used an EBDC
(Polyram, Dithane, Maneb, etc.) through the entire scab season, which
would have handled rust. The SI (Nova) would provide good post-
infection activity against rust as well as scab, so I doubt the
infections happened early.
On Apr 29, 2009, at 4:37 PM, Karl Townsend wrote:
After 28 years of growing, we had our first serious rust infection
last year. In the past, the thought always has been: control scab,
you won't get rust.
There was virtually perfect scab control last year. We pay great
attention to the mills table and try to spray just ahead of wetting
periods when not protected. I do remember we got caught once last
year and went in 24 hours after rain had started, not that unusual
an occurance(and the reason for back to back Nova). Scab materials
are polyram, polyram/nova (twice) and then captan. One spray of
scala to end the season. Five applications last year.
My question, is there a time or growth period when rust control
using scab control methods is known to not work?
Karl , grower in central Minnesota,USA
--------------------------------------------------------------------------
The 'Apple-Crop' LISTSERV is sponsored by the Virtual Orchard <http://www.virtualorchard.net
> and managed by Win Cowgill and Jon Clements <webmas...@virtualorchard.net
>.
Apple-Crop is not moderated. Therefore, the statements do not
represent "official" opinions and the Virtual Orchard takes no
responsibility for the content.
--------------------------------------------------------------------------
The 'Apple-Crop' LISTSERV is sponsored by the Virtual Orchard
<http://www.virtualorchard.net> and managed by Win Cowgill and Jon
Clements <webmas...@virtualorchard.net>.
Apple-Crop is not moderated. Therefore, the statements do not represent
"official" opinions and the Virtual Orchard takes no responsibility for
the content.
