Apple Pest Report: Tuesday,
May 8, 2007
Vol. 15 No. 3
Growth stage
Here
are updated forecast phenology dates for McIntosh at Highmoor Farm. For what its worth, after the above
normal temperatures this week come to an end with lower temperatures and
potential rain on Friday-Sunday, May 11-13, the longer term forecast for May
16-22 calls for a cooling trend.
|
McIntosh (and similar cultivars) Growth Stage |
Estimated date |
|
Tight Cluster |
May 8 |
|
Open Cluster |
May 9 |
|
full Pink (extended
petioles) |
May 12 |
|
King Bloom |
May 18 |
|
Full Bloom |
May 20-21 |
|
95% Petal Fall |
May 27 |
|
100% Petal Fall |
May 29 |
|
Fruit Set |
June 2 |
Apple Scab
It seems that I can always come up with a reason to
worry about the apple scab situation, even in what has so far been a dry
spring. Here is the current version
of ascosporic angst. In a typical year
growers will have put on two or three fungicide applications before a scab
infection period at Pink. To reduce
the muddle in our fevered brains, we reduce fungicide spray decisions to
simplified rules such as “A full dose captan application prevents scab
for 7 days or 2 inches of rain, whichever ends first.” Those rules work,
but reality is probably a bit more complex.
I’ve heard at least
on prominent plant pathologist opine that multiple protectant fungicide sprays
have a cumulative longer term effect than their immediate 7-day protection
period. These multiple applications
provide some correction for imperfect spray coverage in any single
application. When a major infection
period hits at Pink, the rain redistributes the cumulative fungicide dose on
the foliage. Most of that fungicide
is from the most recent spray of course, but there is some contribution from
early sprays as well.
Now consider the situation
this year. My guess is that many growers
applied fungicide before the rain on April 27 when apples were between Green
Tip and Half Inch Green at all but the latest Maine locations. Given the earliness of that infection
event, other growers may have not sprayed for it. In either case, there is virtually no
leftover fungicide from earlier sprays to supplement the fungicide that I hope
you are planning to apply before the rain forecast to begin Friday morning, May
11. That is because there was very
little green tissue to capture fungicide deposit when that earlier application
was made. Since then we’ve
had 10 days of foliar expansion to dilute through spreading whatever fungicide
residue did remain after the 1.5 inch of rain received April 27-30. Clusters at Pink during a rain this
coming weekend will provide a much bigger landing target for scab ascospores,
and the susceptible foliar tissue being exposed with each passing day has not
any prior fungicide coverage, and isn’t going to benefit from residue
from earlier sprays redistributing to help prevent new infection.
Orchards that have received
a fungicide application since April 30 do not fall into this category, and for
those sites, if the rain arrives as forecast, then Friday – Sunday will
be a significant infection period representing about 20-25% of the
season’s total primary scab infection risk. That is a risk that needs attention, but
it is not extraordinary. We have a
couple of big infection periods like this every year. It is only the locations with only one
previous early season fungicide application this year that are the subject of
this additional concern.
The remedy for that concern
is nothing unusual. The concern
just increases the incentive to encourage excellent coverage for renewed
fungicide protection before the next forecast rain. That is because that application alone
is providing all the protection you will have in place. There is no redistribution from early
coverage to compensate for less than perfect coverage by an application made in
the days before the next rain.
Scab infection period
ratings for Highmoor Farm and vicinity are available in chart
and table
form. The whole list
of Orchard Radar estimates are online at http://pronewengland.org/AllModels/MEmodel/RADARME-Monmouth.htm
Insects and Mites
I’ll
be checking traps at Highmoor Farm tomorrow, but the scab situation called for
getting this newsletter sent ahead of the Wednesday and Thursday morning spray
window before the rain forecast for Friday, so I don’t have those numbers
to report. If the Tarnished plant
bug (TPB) or Leafminer traps show anything dramatic, I’ll send an
addendum tomorrow night, but I don’t expect that to happen.
As mentioned last week, leafminer populations are so unpredictable
that I prefer a “wait and see at First Cover” approach regardless
of what the traps show. But the
traps are useful to provide early warning.
As for TPB, trap counts can be useful to indicate if a Pink
insecticide might be justified in a monitored block. In recent years at Highmoor, TPB trap
counts in most monitored blocks have not been over threshold. TPB can vary greatly between blocks even
on a single farm, and certainly between distant orchards in different settings
with respect to surrounding host vegetation. So there is probably limited scientific
value in reporting Highmoor Farm trap counts to growers spread around the state
of Maine. But as with leafminer
traps, that information has some use as anecdotal fodder about whether TPB are
generally higher or lower this year.
If you don’t have your own traps up, check your trees for buds
oozing a drop of clear/yellowish liquid.
That is an indication of recent TPB feeding.
Regarding TPB, the following quotes are excerpts from a recent
newsletter article by Dr. Art Agnello, Cornell University:
“According to your personal philosophy, RAA and TPB can be either perennial challenges, puzzling but non-fatal
occurrences, or else a complete flip of the coin. Do you have them, do you need
to treat for them, are you able to control them if you do, and does it matter
if you don’t?”
“You’ll have to decide for yourself whether this bug
is of sufficient concern to you to justify treating. We have seen few orchards
in western NY where TPB control is warranted (and only slightly more in the Hudson
Valley), simply because the most effective treatment to use is still a
pyrethroid, which a) kills predator mites, and b) still rarely lowers TPB
damage enough to be economically justified.”
“…consider
potential impacts on non-target species such as beneficials, and be aware of
your bee supplier’s concerns about effects on pollinating bees.”
2007 New England
Tree Fruit Pest Management Guide
The 2007 edition of the guide has been mailed and
should be at Highmoor by May 10. Dr.
Renae Moran will send out order forms in her newsletter.
Scouting Co-op
I still don’t have anyone hired to be the
Apple IPM Scout. If you know of a
person at least 18 years old with a Maine driver’s license, a clean
driving record, and who lives within commuting distance of Highmoor Farm,
encourage them to pick up an application at Highmoor Farm, or to give me a call
at 207-581-3882.
Meeting
announcement
Apple growers in some of the other Northeast states get government
support for IPM activities and expenditures. It would be nice to have that working
for us in Maine. The following
workshop is a step in that direction.
While the workshop is about vegetable and small fruits, even apple
growers who do not grow those crops might it find it an interesting
introduction to Natural Resource Conservation Service (NRCS) farm support programs.
On-Farm Workshop Will Link IPM
Practices With NRCS Goals
On June 25, the Maine
Department of Agriculture will host an on-farm workshop that demonstrates
conservation-based integrated pest management (IPM) practices for vegetable
production. Funded by USDA-CSREES through the Northeastern IPM Center, this
workshop will focus on using IPM practices to promote NRCS conservation goals, with
the objective of helping growers improve crop yield and pest control while
minimizing environmental impacts. Participants will
learn how IPM and conservation practices complement one another and benefit
vegetable production, and how growers can earn financial assistance from NRCS
for using IPM practices. Topics will include: cover cropping, insect and weed
identification and management, soil quality, economic thresholds, pest
monitoring, zone till demonstration, conservation planning and practices, and plant
nutrition and health.
WHEN AND WHERE
The workshop will be held June 25, 2007 from 9:00 AM
to 3:30 PM at two vegetable farms located in the central coast region in Nobleboro and Jefferson, Maine. See attached flyer for
details.
WHY YOU SHOULD ATTEND? Growers will learn about different IPM
practices and their conservation benefits, and how NRCS conservation programs
can help their farms
Sincerely,
Glen
Glen Koehler
Pest Management Office
491 College Avenue
Orono, ME 04473
Voice: 207-581-3882
Email: gkoehler@umext.maine.edu
Web: PRONewEngland.org
Fax: 207-581-3881
What we call the secret of happiness is no more a secret
than our willingness to choose life.
- Leo Buscaglia