Hi Art
There is no OBLR pheromone trap treatment threshold that I know of. As
Jon said, the traps are used for timing not threshold detection.
That said, and with a big "buyer beware" cautionary note that we really
can't extrapolate from one pest to another, I still find it "informative"
to note that the MidAtlantic Orchard Monitoring Guide mentions three
pheromone trap based thresholds for apple Lep pests: Codling moth (5 CM
per week per trap), Tufted apple budmoth (roughly 15 TABM per trap per week
based on Figure 11.1), and Lesser appleworm ( 5 LAW per trap per week,
which is based on the CM threshold, so maybe we can extrapolate between
pests!).
The problem with using pheromone traps for thresholds is that the traps
attract males and the pest population depends on number of females laying
eggs, and the number of larvae of both sexes, neither of which may be very
well correlated with male captures in pheromone traps. Add in the
variability caused by trap placement, wind direction, flight temperatures
etc., and it's not hard to see why pheromone traps are more useful as
presence/absence detectors for timing degree day models to estimate optimum
time for direct observation than for making population density measurements.
When populations are low, I don't even trust pheromone traps that much
as biofix detectors unless a large number of traps are used and are
regularly checked. My concern there is that with a low population and an
inefficient trapping system, the appearance of moths in the traps may be
delayed past the date when emergence began. Thus it may be better to use
both degree day model to estimate the adult emergence date or other biofix
and trapping and compare them to decide which seems more realistic for
setting biofix for subsequent degree day estimate to identify optimum
sampling date. Of course, is the population is high, only the pheromone
traps will indicate that.
My guess is that 7.5 per trap is definitely enough to schedule time for
making larval count, but not enough to lose sleep over until you get those
scouting results. The threshold for larval observation is 3 infested
terminals with living OBLR larvae per 100 terminals checked. The degree
day estimate for start of OBLR flight at Sanford Ag-Radar site near you was
June 18. Based on that, the optimum sampling date is July 11, with a July
15 followup if the first check is below threshold. ( I don't think the
July 3 egg hatch date is relevant because your trap catch levels are not
high enough to indicate convincing need for treatment, so better to wait
for scouting observations.)
I entered your June 20 biofix and that nudged the optimum scouting
date to July 13 with July 17 followup. We'll make that part of the
scouting visit that week, but we will only be able to do one check vs. the
recommended two check protocol.
- Glen
On Tue, Jul 1, 2014 at 6:25 PM, Jill Kelly <[email protected]> wrote:
> Thanks Jon.
> On Jul 1, 2014, at 12:42 PM, Jon Clements wrote:
>
> Art, there is no "threshold" as far as I know. Pheromone traps are
> typically used to establish a biofix to time the best treatment. See:
>
> http://www.fruitadvisor.info/tfruit/clements/models/oblr.html
>
> According to AgRadar, you should be out spraying for this pest July 3 so
> you can relax on the 4th. But, your namesake tropical
> depression/storm/hurricane Arthur may have something to say about that too!
>
> http://pronewengland.org/AllModels/MEmodel/ME-Sanford-InsectDates.htm
>
> Jon
>
>
> On Mon, Jun 30, 2014 at 2:55 PM, Arthur Kelly <[email protected]>
> wrote:
>
>> Is there a treatment threshold for pheromone trap captures for OBLR? We
>> averaged 7.5/trap today. We trapped the first adults on 6/20, one per trap.
>>
>> --
>> Art Kelly
>> Kelly Orchards
>> Acton, ME
>>
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>>
>>
>
>
> --
> Jon Clements
> aka 'Mr Honeycrisp'
> UMass Cold Spring Orchard
> 393 Sabin St.
> Belchertown, MA 01007
> 413-478-7219
> umassfruit.com
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>
>
>
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>
--
Glen Koehler
University of Maine Cooperative Extension
Pest Management Office
Voice: Office 207-581-3882, Cell 207-485-0918
491 College Avenue, Orono, ME 04473
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