The first version (2005) of the
RIMpro-Cydia model is structured according to common knowledge and
literature data on biology of the codling moth. The principal structure
of the model is given in the flowdiagram.
Although the model is a
population model and has quantitative aspects, these are only used to
derive the biology of the codling moth in a qualitative way. For a real
quantitative model, much more information on the starting population,
reproduction and mortality of the insects as well as effects of crop
protection management practices is necessary. Most of these factors are
highly local.
Apart from the basic structure,
most of the simulation parameters can be changed by the user. This is
meant to test for susceptibility of the simulation outcomes for
different parameter settings. Normal users should play around with this
and relay on the basic settings.
Accuracy of input data
Special care should be taken for
the accuracy of the temperature measurements as most processes in the
program are temperature driven. As processes are simulated over a longer
time, errors in measurements accumulate. 0.5 °C temperature difference
ands op in 50 HU difference in developmental time half way summer
which leads to a shift of more then a week!
As flight takes place during a short period in sunset, the time readings in your dataset should be accurate The program expects local summertime.
Diapausing larvae
The model starts with an
population of over wintering codling moth larvae. These larvae end their
diapause during spring, and pupate. In the model these two processes are
combined to one process that leads to the emergence of female moths. The
process is driven by a non linear temperature relation according to the
curve in figure 1. The cure was constructed using data from different
sources. The same curve is used for the other temperature related
processes. 1st of January is chosen as Biofix for the model.
Principally the model needs a complete set of weather data beginning 1st
of January. As there is no development below 10°C, this date is
relatively arbitrary, and it wont disturb the outcomes when then model
is run with a dataset that starts after 1st of January as
long as it start before air temperature comes above 10°C for more then a
few moments per day. The average process length is 260 Heat Units. With
a relative dispersion of 0.25 the very first female moths in the model
emerge around 100 Heat Units. But they will not been seen in the model
(and not in the field) until the evening conditions allow for the first
flight.
Flight of unmated females
Newly emerged females need the
chance to get mated before they can lay their eggs. For this they need
probably one or two evenings with suitable flight conditions. This pre-oviposition
period is in literature however mostly described as a temperature sum
over 10°C between emergence and first egg deposition. This period is
reported as on average being longer for the first generation that for
the second generation. Which is logical, as most probably the females
that emerge in spring have on average to wait longer uniting flight
conditions are suitable than the females for the second generation.
Although in future versions of
the RIMpro-Cydia model it would be better to define the pre-oviposition
time as a relation to (evening) flight conditions, in the current model
version the pre-oviposition period is described in the traditional way
as a number of heat units.
The flight activity
From geographical position and
date, the program calculates the time of sunset. The window of possible
flight activity is predefined (but user adjustable) from 60 minutes
before until 120 minutes after calculated sunset. This is probably to
long and should be zoomed in to get maximal performance of the model.
During active rain flight activity is zero.
Within the window around sunset,
and under the condition that it is not raining, the relative flight
activity is depending on air temperature. Flight activity increases
gradually form 12 tot 20 °C , an decreases above that. (figure 2)
The flight activity per hour in
the model is calculated as number of living females * relative flight
activity.
Egg deposition
Almost all information on flight
activity refers to the mating flight of male moths. Most egg deposition
by mated females seems to take place in the same time interval around
sunset, but also partly around sunrise and to a very limited extend also
on other moments during the day. Within the model eggs are only
deposited during the sunset window. Egg deposition requires higher
temperatures than (male) flight activity. The temperature relations for
the flight and egg deposition process for the model drawn in figure 2
are interpretations form data from various sources. The user can not
change these relations.
Mortality of female moths
As the female moths deposit
their eggs in the first 7-10 days of their live, they are given an
active live of 30 Heat Units, with a relative dispersion of 0.1. After
that, they are of no importance for the reproduction anymore, and
disappear in the model. In reality male and female moths may live
longer and can still be captured in the field, but do not contribute to
the next generation anymore.
Embryonal development
Embryonal development time is
relatively well documented in literature. The preset values in the model
are an average of 88 Heat Units, and a relative dispersion of 0.1.
Larval and pupae development
The preset value for total
larval development is an average of 300 Heat Units, and 160 Heat Units
for pupation. Both processes have a relative dispersion of 0.1.
Questionable is whether the larvae that develop in the fruits receive
the same temperature as the air temperature that we measure and use as
input for this model. This is almost sure a source of deviation between
model outcomes and field data.
Diapause induction
The model accounts for a poly
votile population. Individuals that reach 300 Heat Units of their larval
development before the critical day length pupate the same year and form
a second generation. Larvae hat reach this developmental stage later,
stop their development en pupate next spring. 1st of august
is preset as critical date for diapause induction, with a RD of 7 days.
Success rate
As there are no mortality
factors for the first generation included in the model. To prevent the 2nd
generation to over flood the program procedures, an arbitrary fraction
0.01 is set as success rate for the first generation.
Bio Fruit Advies Dorpsstraat 32 4111 KT Zoelmond marc.trapman@biofruitadvies.nl