Apple Pest Report: Tuesday,
May 22, 2007
Vol. 15 No. 4
Growth stage
McIntosh
trees at Highmoor Farm are at full bloom.
Cortland and Red Delicious are in early bloom. Gala and Honeycrisp are at King Bloom.
|
McIntosh (and similar cultivars) Growth Stage |
Estimated date |
|
95% Petal Fall |
Sunday, May 27 |
|
100% Petal Fall |
Tuesday, May 29 |
|
Fruit Set |
Saturday, June 4 |
Apple Scab
The
rains on May 15-20 have posed some challenges for maintaining protection. Many growers took advantage of suitable
spraying weather to update protection during the break in the rain on May 17. Blocks that received last received
fungicide on May 12-14 without a refresher on May 17 should have had protection
through most but not all of the May 15-20 stretch of rain.
In low inoculum orchards where a properly
calibrated sprayer applied a full dose of captan or EBDC fungicide good canopy
coverage on May 12-14, even without the a May 17 refresh, there was probably
adequate production to last through the rain ending Saturday night/Sunday
morning May 19-20.
Of
course, as with any apple scab discussion it is all a question of numbers, or
more specifically a matter of percentage.
High inoculum orchards have so much more scab infection potential that
even a tiny fraction of the season’s spore load released during a time of
questionable protection represents a serious infection risk. And the very factors that led the orchard
having high inoculum load, unless corrected, can exacerbate the situation and
increase the infection risk again this year. If the high inoculum status this year is
from poor scab control last year caused by trees that were too large and thick,
or the sprayer fan too weak, or the amount of water used to carry fungicide too
little (i.e. concentrate spraying over 8X), or travel speed too fast etc. etc.,
and those constraints still apply, then scab control can be poor again this
year.
Petal
Fall is a good time to reevaluate sprayer output. Measure gallons per minute output, and
combine that with travel speed, tree row volume, and row spacing to find out
how accurate the overall pesticide delivery system is. With shoot elongation, sprayer delivery
errors that do not cause problems in covering sparse prebloom canopies can lead
to control problems when matched up against the far more challenging task of
getting good coverage on increasingly thick canopies and exposed fruit from
Bloom onward. Yes this is an
article about scab, but sprayer calibration is at least as important as
understanding scab biology or fungicide chemistry in preventing scab
infections.
Even where protection was
renewed on May 17, foliage newly emerged foliage will be beyond the range of
fungicide redistribution and vulnerable by the time the next rain. The current forecast (Tuesday night, May
22) shows low probability of rain from Bangor south until Monday, May 28, and
even that looks like a 50:50 proposition at this point. (Takes a minute to get used to, but a
great site to see rain probability for 12 hour intervals for coming 8 days is
at http://www.nws.noaa.gov/mdl/forecast/text/state/ME.MRF.htm)
Technically,
as long as there is very low chance of rain, then there is no need to reapply
fungicide. Practically though, some
growers have too much acreage or too little flexibility and rapid-response
capability should the forecast shift to play that game. But if you do have that flexibility, the
longer you wait to reapply fungicide the later that application will last when
it eventually goes on.
However
you get there, be sure to have solid fungicide protection in place before the
next rain because (barring a short quick-drying shower) it will bring with it
the most severe infection pressure of the year. At Highmoor Farm, all of this
season’s scab infection periods account for about 35% of the total
infection pressure. Another 25% is
ready to go and waiting for rain right now. With the high temperatures coming later
this week, by June 1, the whole of the remaining 65% will be ready to go.
And
with apple fruit tissue developing, infections from now on bring the risk of
spores landing directly on fruit.
And to top it off, any lesions that started during the early season
infection periods will start producing second generation conidial spores
starting around May 26 with the full 35% of previously release infection
potential into secondary scab cycle by June 1. The next scab infection period will be
the last big one of the year, but it will go out with a bang.
Sterol
inhibitors, despite the risk of resistance discussed in previous issues, are
still the best bet for long range kickback in most Maine orchards. But they are a very poor choice for this
situation where protective durability is the key. Captan, and EBDC (Dithane, Penncozeb,
Manzate, Polyram) and strobilurins (Flint, Sovran) are the best protective
options. If you get caught short on
protection when the next infection arrives, that’s when to consider
postinfection control with an SI (Indar, Nova, Rubigan, Procure) + protectant
fungicide combination.
Blossom end rot and Fire blight
Weather
during late bloom through Petal Fall for most orchards does not seem to pose
high risk of blossom end rot this year.
The temperatures into the
80s forecast for Thursday and Friday create high potential for fire blight
infection IF (and only if) there is rain or heavy dew on Friday, Saturday May
25-26. Rain or heavy dew on May 27
or 28 might also be enough to initiate conditions but the risk on those days is
lower. Fortunately there is no rain
or heavy dew in the forecast for any of those days. With scab and fire blight both ready to
hit hard, this is definitely a week to watch for rain in forecast.
If
it does look like rain, you would want to seriously consider applying
streptomycin to Gala, Honeycrisp, Gingergold, Golden Delicious, PaulaRed and
other susceptible cultivars, and to any tree on M26 or M9 rootstock. If it did rain on May 25 or 26, the
timing would be perfect for a serious fire blight blossom infection. This is because the heat units are
accumulating when most cultivars are between Full Bloom and Petal Fall.
This
situation is almost a rerun of the hot spell on May 8-10 that ended with
serious fire blight conditions on May 11 in Rhode Island, Connecticut and
Massachusetts. That event was no
problem for Maine because we weren’t into bloom yet. A lot of streptomycin was sold and
applied in Massachusetts over a few days prior to May 11. Apparently growers there have seen
enough fire blight to not want to see any more. By next week, apple growers in southern
New England will be able to tell if fire blight infections took hold.
As with any disease, it
takes inoculum in addition to susceptible host and suitable environmental
conditions. Nobody knows how much
fire blight inoculum there is in Maine orchards overall, but there are several
growers who can testify that the bacteria does live in here because
they’ve seen infections in their orchards in recent years. If the forecast for May 25-28 was not
looking as dry as it does tonight, I’d be more worried. Let’s hope that this week’s
little heat spell is just another trial run showing us that we can get the
temperature conditions during bloom to support fire blight, but that nothing
else comes of it because it stays dry on the critical days.
Insects and Mites
Prebloom trap captures of
Tarnished Plant Bug and Spotted Tentiform Leafminers at Highmoor Farm were very
low this year. It is too early to
judge European Apple Sawfly (EAS) captures, but as of Monday May 21 when
McIntosh were a day short of full bloom, only one EAS had been caught on 14
traps that had been set at Pink in four different blocks. EAS have been much more numerous by
bloom at Highmoor in past years, but the final trap capture comparison against
threshold is not made until Petal Fall.
With the hot weather later this week, that single trapped EAS could turn
into many.
Keep an eye out for various
caterpillars that can become numerous at this time of year. Normally the damage they cause is
insignificant, but if more than 5% of fruit clusters are affected, you may want
to consider control options. If an
insecticide is needed and trees are still in bloom, a Bt insecticide can
control caterpillars without harming bees and other pollinators.
Green fruitworm, Eastern
tent caterpillar, Winter moth, Green pug moth, Gypsy moth, and Obliquebanded
leafroller are all possible visitors.
For tent caterpillars, the best control is just to remove the nests by
hand as getting spray penetration is difficult.
Mullein
plant bug (MPB) is one of the most exasperating apple insect pests because it
strikes so infrequently and because they are difficult to monitor until the
time at which they have already started to create damage. Normally they are beneficial mite
predators, but in some years, probably due to synchrony between MPB egg hatch
and availability of young apple fruit in the absence of mites to feed on, MPB
feed on apples leaving warty bumps.
Red Delicious is a favorite cultivar and unfortunately Reds react to the
damage more severely than other cultivars, becoming defaced and misshapen. The best you can for this best is to
check Red Delicious trees during late bloom by tapping 20 limbs in a block over
a two-foot square beating tray. If
doing this dislodges more than 8 fast moving aphid-like light green MPB nymphs,
they consider either an early evening application of Assail (timing to minimize
bee hazard). Petal Fall application
of Actara or a pyrethroid are other options.
Last but not least, the
main insect threat at Petal Fall is the mysterious plum curculio (PC). PC don’t usually start laying eggs
in apples until the fruit reach 7mm diameter, but delaying insecticide
protection more than a few days past Petal Fall makes the spray too late to
prevent initial EAS damage.
Standard procedure is to make a full block insecticide application after
bee hives have been removed and after petals have fallen, followed by one (or
two if weather turns cool and wet) perimeter applications to kill later
immigrating PC.
There
is an excellent overview of PC and other Petal Fall apple pests in this week's
Scaffolds newsletter by Dr. Art Agnello, online at http://www.nysaes.cornell.edu/ent/scaffolds/2007/070521.html#i2
Other News
New England Tree Fruit Pest Management
Guide
The 2007 edition can be purchased by sending a
check for $35 made out to Cooperative Extension to Highmoor Farm, PO Box 179,
Monmouth ME 04259.
Scouting Co-op and Orchard Radar
I am very pleased to announce that Rebecca Bubier
has been hired as the Maine State Pomological Society – Cooperative
Extension scouting co-op scout. Rebecca
will be calling next week to arrange introductory visits to growers who have
signed up for free weekly or bi-weekly visits to scout for apple scab, mites,
leafminers, leafhoppers, and apple maggot.
This is last call to sign up for scouting. Because of the travel logistics, it is
difficult to change the schedule once it is set. If you want scouting please sign up now. I can’t guarantee we can
accommodate late signups.
Good Agricultural Practices GAP Certification
Requirement
Beginning July 1, 2007,
GAP certification will be required for any fresh produce purchased by USDA
feeding and nutrition programs. As
I understand it, starting January 1, 2008 anyone wants to sell apples to
Hannaford Brothers (Shop & Save) will have to be able to provide GAP
certification. At a recent workshop
the news was that GAP is here to stay and other buyers will be requiring it
sooner than later.
Dr.
Steven Johnson, UMaine Cooperative Extension Potato Crops Specialist has taken
the lead on this. For a quick
intro, read his abstract from the winter potato meetings at http://www.umaine.edu/umext/potatoprogram/upcoming/abstracts.pdf
For
information on what certification requires, see the information Dr. Johnson has
developed and placed online at http://www.umaine.edu/umext/potatoprogram/gap_good_agricultural_practices.htm. That info is oriented to potato
production, but the same templates can easily be adapted for orchard use.
Workshop
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. Contact Dr. Kathy Murray,
Maine Department of Agriculture for details: 207-287-7616, kathy.murray@state.me.us
WHY SHOULD YOU 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