Evaluation reinvented
Modeling and density estimation of Heterodera schachtii populations
Interval of density by the choice of crop rotation and no of generations, a parsimonious difference equation
Formerly a Java applet for online applications have been placed at this position. The security demands of Java or browsers of today are so strict, the applet does not even run on my own computer anymore. Alternatively, we produced the results graphically for all combinations available and provide the basic backgrounds.
The model predicts the long term dynamics of BCN Heterodera schachtii
on a discrete year axis. An initial value of the population Pi is required. The following difference equation
calculates the population size
at year n+1 as a function of the Pi value at n, the number of generations and the type of cultured crop. This autumn
value is reduced by a constant overwintering rate pov (= 0.6) determining the target size eggs & juveniles/100 ml soil
for the next spring. The population decreases under the chosen non-host of the crop rotation with certain probabilities, and
finally results in a Pi value at pre-planting next time sugar beet.
The objectives are to keep the population density of BCN below the threshold level of 500 E&J/100 ml soil at planting sugar beet.
The images reflect the hypothetical frame of the population dynamics as controlled by the simple input variables. The "real" dynamics
are somewhat within these confidence interval.
