[NAFEX] Definition requested
list at ginda.us
Mon Apr 23 21:19:38 EDT 2007
The low-tech way to do the approximate the same thing is to learn which
plants react to temperatures similarly to whatever you need to monitor.
For instance, yard-care people will tell you the time (in NE) to spread
pre-emergent weed killer on the grass is when the forsythia blooms, or a
bit before. I have a problem with winter moths. Last year I caught them
the day they hatched on the apples by careful observation. This year I
remembered that they hatched when the scilla first opened, and the apple
bud scales bagan to separate. So I timed my first spray accordingly.
Judging by the size of the dying caterpillars I found the next day, I was
one or two days past the optimal time, but the prior two days had been both
work days and rainy, so I figure I did about as well as I could.
If you are a commercial farmer, degree day models probably work better.
But if you are a weekend backyard gardener, watching the plants is a decent
...... Original Message .......
On Mon, 23 Apr 2007 19:27:06 -0500 <dmnorton at royaloakfarmorchard.com> wrote:
>Sorry guys! I'm so used to working with these timing devices I forget
>a lot of folks are not familiar with fruit tree phenology. If you visit
>http://www.nysaes.cornell.edu/pubs/fls/OCRPDF/58a.pdf you will find nice
>color photos of the growth stages of fruit trees and at
>http://extension.unh.edu/pubs/HGPubs/Gsftdb.pdf where you can see all the
>different varieties of fruit on one black and white chart.
>Growing Degree Days (GDD) is a heat index that relates the development of
>plants, insects, and disease organisms to environmental air temperature.
>index varies depending on whether it is a cool, warm, or very warm season
>plant. For example, a corn growing degree day (GDD) is an index used to
>express crop maturity. The index is computed by subtracting a base
>temperature of 50 degrees F from the average of the maximum and minimum
>temperatures for the day. Minimum temperatures less than 50 are set to 50,
>and maximum temperatures greater than 86 are set to 86. These
>indicate that no appreciable growth is detected with temperatures lower
>50 or greater than 86. If the maximum and minimum temperatures were 85 and
>52, you would calculate the GDD by ((85+52/2) - 50) = 18.5 GDD.
>290 GDD50 means 290 Growing Degree Days based on 50 degrees F lower
>threshold. For example:
>Our codling moth program includes pheromone traps used to monitor 1st
>generation flight. Biofix is reached on the date of the first sustained
>catch which means trapping moths on 2 consecutive days and using the date
>the first catch prior to the second catch. If I catch moths on April 24,
>and 27, my biofix date would be April 26 because I did not catch any on
>April 25 so there was no sustained catch until April 27. My weather
>monitors the daily temps every 10 minutes, establishes the daily low temp
>and daily high temp from the date of biofix forward, calculates the DD
>(Degree Days), then uses the 50 degree DD base model to time sprays for
>1st and 2nd generations.
>My codling moth program for this season is:
>100 DD..............................Place traps in orchard
>150-200 DD.......................First moths expected to fly, check traps
>every day until biofix is established
>50-75 DD after biofix..........Pre-egg laying: Spray Rimon .83EC
>100-200 DD after biofix......Early egg laying: Spray Superior oil or
>220-250 DD after biofix......First egg hatch: Spray Assail
>340 -640 DD after biofix.....Peak egg hatch (80%) Critical protection
>period: Spray Imidan
>Plum Curculio also emerges around this time so Imidan is used for both pests
>at same time.
>Everything is based on temperature. A certain sustained temperature is
>necessary for the eggs of insect pests to hatch; in the case of codling
>moth, 50 DD.
>Oblique Banded Leaf Roller is a base of 43 DD
>Oriental Fruit Moth is 45 DD
>Plum Curculio is 50 DD
>Spotted Tentiform Leaf Miner is 43 DD and so on.
>Tree phenology is not the most efficient method to use, but is based on
>degree days as well. But when we get weather like we have had this
>the trees can take giant leaps in phenology within 24-48 hours. This
>weekend we went from 1/4" green to pink from Saturday (high 75) to Sunday
>night (high 77). During that same time we picked up 27 DD, but are still
>only 148 DD for the year. I expect to begin seeing codling moths this
>if we reach 200DD.
>Hope this helps explain some things!
>Royal Oak Farm Orchard
>----- Original Message -----
>From: "Jim Fruth" <jfruth at tds.net>
>To: "NAFEX" <nafex at lists.ibiblio.org>
>Sent: Saturday, April 21, 2007 7:47 AM
>Subject: [NAFEX] Definition requested
>> What does "shuck split" mean?
>> The critical timing period for plum curculio has historically been at
>> set just as the fruit begins to swell. However, recent research has shown
>> that plum curculio females are reproductively mature well in advance of
>> stage. We estimate 95 percent of the females are mated after 290 GDD50,
>> which is typically right at shuck split in stone fruits and fruit set in
>> pome fruits. Females are ready to oviposit long before fruit are large
>> enough to support the developing larvae.
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