[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 
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
----- 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.

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