Pessl Instruments C.beticola Risk Model
Bleiholder and Wetzien 1972 where looking deep into the reproduction of C.beticola. They found the pathogen to be well adopted to warm climate. Latency period and sporulation was strictly temperature dependend and the temperature optimum was found to be quite high. The findings of Wolf, P.F.J. et all (2001) where very similar to those of Bleiholder and Weltzien (1972). At temperatures below 14°C incubation period becomes longer than 14 days. If temperature undergoes 10°C there is very few progress in fungal development and at 5°C no fungal development is visible at all.
This explains the late occurence of the pathogen in the sugar beet fields in cool climate. Looking for publications made in the actual century we will find even for cooler places that C.beticola can be found to the end of June. Going back to the seventies and eighties of the last century C.beticola was found in this places during July and first sprays had to be applied at the end of July and the beginning of August.
Bleiholder and Weltzien where looking for the impact of temperature on conidia formation too. They found very few conidia formation below 15°C but an optimum of 25°C and 30°C. Wolf et al (2001) where looking for the germination and they found optimum temperatures at more than 22°C.
The simple risk model uses this findings to evaluate if we can expect C.beticola at all. For this it looks first if the incubation period could be fulfilled within the last 2 weeks. If yes we get 100% of incubation if not the percentage of incubation within the last 2 weeks will be below 100%. Beside of the incubation model the risk model uses a model for sporulation. Optimum Conditions of 48 hours of high relative humidity with an average temperature of 30°C is used as 100% sporulation.
The risk is 0 if the incubation period has been found to be longer than 2 weeks. If this is not the case the model output will be 1. If there si a sporulation model result of higher than 10% calculated within the last week the risk will be shown to be 2 and if the sporulation result is higher than 30% the risk will be outputted to be 3. If we are looking for the model result, here for the year 2010 for a iMETOS located in Styria Austria we can find the risk model displayed together with the DIV model. Both models will indicate the first reasonable risk and the first DIV values accumulated to 6 on two consequent days for the middle of June. This would indicate the first spray for susceptible varieties on this site. Moderate susceptible varieties could be sprayed a little later best in the beginning of the next period with high risk and DIV values.