Nemaplot hyperspectral data analysis and population modellingEvaluation reinvented

 

Modeling the population dynamics and population density estimation of the beet cyst nematode Heterodera schachtii

Damage beet cyst nematode
Field symptoms of H. schachtii
Growth reduction by H. schachtii
Heterodera schachtii Cysts, eggs, Juveniles
Sugar beet canopies with BCN

Population density estimations of the beet cyst nematode (BCN) Heterodera schachtii are extremely tedious in field situations. Not only taking soil samples and the preparation in the lab, but also the counting under the microscope is simply a torture. In short, estimating the nematode population is cost intensive, defective and determined by a high variance due to spatial heterogeneity in the field and numerous other sources. Coefficient of variation above 100% are common. Nevertheless, the information is urgently needed for integrated nematode management techniques (i.e. choice of crop rotation, intercropping, nowadays the use of nematizide are of interest again). The all time objectives of the Nemaplot project have been to reduce the massive work load without loss of information. We developed different strategies on different scales and and build a parenthesis from the research of 1990 to remote sensing technologies of today. Starting with some parsimonious, discrete approaches, to more complex Leslie models, up to application of non-invasive methods as hyperspectral reflectance measurements of sugar beet canopies. As fascinating as hyperspectral measurements are, the full potential with respect to the H. schachtii density estimation problem is exploited by the combination of both, a Leslie model and the methods of hyperspectral reflectance data analysis. Hence, we see it of importance to report right from the beginning, even as it means to go back as far as 1990.

Project overview:

Chronology of model development, background, motivation ... more



What are the long term implications by choosing a certain type of crop rotation? A simple difference equation model for a start ... more



What happens during the season? Modeling the populations dynamics of H. schachtii under sugar beets with respect to the seasonal temperature pattern ... more



Which age-structured distributions are generated by the Leslie model? Each development stage is important ... more



Where the parameter estimates of age structured Leslie models are coming from? Beside a common calibration procedure to long term data, we used data from related experiments under constant temperatures in the range from 12°C to 30°C. These data determine both some of the transition probabilities from one stage to the next and the development rate of the stage. The temperature dependent development rate of the host has been determined ... more



How does the host-parasite interaction vary with different temperatures? What are the implications of a certain asymmetry of the host and nematode dynamics. The system explains some of the observations at higher temperatures of today ... more



A small (unplanned) excurse and contribution to the climate change or global warming discussion. The immediate comparison of the nematode population dynamics controlled by temperatures from 1970 to 1990 and from 2011 to 2014 promises a bright future for H. schachtii. Not for the sugar beet ... more



A projection to the future: What are the effects of the predicted temperatures of the coming decades for H. schachtii? Even a moderate temperature scenario increases the probability of population growth drastically and might limit sugar beet production ...more



The next step: applying non-invasive hyperspectral sensor to detect nematode related differences, some (not very promising) lab results ... more



Hyperspectral canopy measurements in the field, testing the possibilities and limits to detect nematode related density differences from sugar beet canopies ... more



Application of hyperspectral data analysis to estimate the populations density of H. schachtii from hyperspectral images ... more



Currently the last step: The parenthesis of Leslie model with hyperspectral data; measurements at the right (biological) time allow the quantification of cysts in the crop by hyperspectral signatures ... more






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