# [NAFEX] Definition requested

dmnorton at royaloakfarmorchard.com dmnorton at royaloakfarmorchard.com
Mon Apr 23 20:27:06 EDT 2007

```Sorry guys!  I'm so used to working with these timing devices I forget that
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. The
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 substitutions
indicate that no appreciable growth is detected with temperatures lower than
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 of
the first catch prior to the second catch.  If I catch moths on April 24, 26
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 station
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 the
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
Intrepid
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 spring,
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 at
only 148 DD for the year.  I expect to begin seeing codling moths this week
if we reach 200DD.

Hope this helps explain some things!

Dennis Norton
Royal Oak Farm Orchard
http://www.royaloakfarmorchard.com
http://www.theorchardkeeper.blogspot.com
http://www.revivalhymn.com
----- 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
> fruit
> set just as the fruit begins to swell. However, recent research has shown
> that plum curculio females are reproductively mature well in advance of
> this
> 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.
>
>

```